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• 251.
Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
Kahler-Poisson algebras2019In: Journal of Geometry and Physics, ISSN 0393-0440, E-ISSN 1879-1662, Vol. 136, p. 156-172Article in journal (Refereed)

We introduce Kahler-Poisson algebras as analogues of algebras of smooth functions on Kahler manifolds, and prove that they share several properties with their classical counterparts on an algebraic level. For instance, the module of inner derivations of a Kahler-Poisson algebra is a finitely generated projective module, and allows for a unique metric and torsion-free connection whose curvature enjoys all the classical symmetries. Moreover, starting from a large class of Poisson algebras, we show that every algebra has an associated Kahler-Poisson algebra constructed as a localization. At the end, detailed examples are provided in order to illustrate the novel concepts. (C) 2018 Elsevier B.V. All rights reserved.

• 252.
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.). KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
Fuzzy Riemann surfaces2009In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 6, p. 047-Article in journal (Refereed)

We introduce C-Algebras (quantum analogues of compact Riemann surfaces), defined by polynomial relations in non-commutative variables and containing a real parameter that, when taken to zero, provides a classical non-linear, Poisson-bracket, obtainable from a single polynomial C (onstraint) function. For a continuous class of quartic constraints, we explicitly work out finite dimensional representations of the corresponding C-Algebras.

• 253.
Max Planck Institute for Gravitational Physics (AEI), Am Mühlenberg 1, D-14476 Golm, Germany.
Université de Haute Alsace, Lab. de Mathématiques Informatique et Applications, 4, rue des Frères Lumière, F-68093 Mulhouse, France. Mälardalen University, School of Education, Culture and Communication.
Construction of n-Lie algebras and n-ary Hom-Nambu-Lie algebras2011In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 52, no 12, p. 123502-Article in journal (Refereed)

As n-ary operations, generalizing Lie and Poisson algebras, arise in many different physical contexts, it is interesting to study general ways of constructing explicit realizations of such multilinear structures. Generically, they describe the dynamics of a physical system, and there is a need of understanding their quantization. Hom-Nambu-Lie algebras provide a framework that might be an appropriate setting in which n-Lie algebras (n-ary Nambu-Lie algebras) can be deformed, and their quantization studied. We present a procedure to construct (n + 1)-ary Hom-Nambu-Lie algebras from n-ary Hom-Nambu-Lie algebras equipped with a generalized trace function. It turns out that the implications of the compatibility conditions, that are necessary for this construction, can be understood in terms of the kernel of the trace function and the range of the twisting maps. Furthermore, we investigate the possibility of defining (n + k)-Lie algebras from n-Lie algebras and a k-form satisfying certain conditions. (C) 2011 American Institute of Physics. [doi:10.1063/1.3653197]

• 254.
Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
On the Chern-Gauss-Bonnet theorem for the noncommutative 4-sphere2017In: JOURNAL OF GEOMETRY AND PHYSICS, ISSN 0393-0440, Vol. 111, p. 126-141Article in journal (Refereed)

We construct a differential calculus over the noncommutative 4-sphere in the framework of pseudo-Riemannian calculi, and show that for every metric in a conformal class of perturbations of the round metric, there exists a unique metric and torsion-free connection. Furthermore, we find a localization of the projective module corresponding to the space of vector fields, which allows us to formulate a Chern-Gauss-Bonnet type theorem for the noncommutative 4-sphere. (C) 2016 Elsevier B.V. All rights reserved.

• 255.
Solid State & Supramolecular Structural Chemistry Unit, Division of Organic Chemistry, National Chemical Laboratory.
Solid State & Supramolecular Structural Chemistry Unit, Division of Organic Chemistry, National Chemical Laboratory. Solid State & Supramolecular Structural Chemistry Unit, Division of Organic Chemistry, National Chemical Laboratory.
Supramolecular synthesis of some molecular adducts of 4,4′-bipyridine N,N′-dioxide2009In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 33, no 1, p. 57-63Article in journal (Refereed)

Molecular adducts (1a–1e) of 4,4′-bipyridine N,N′-dioxide, 1, respectively with cyanuric acid, trithiocyanuric acid, 1,3,5-trihydroxybenzene (phloroglucinol), 1,3-dihydroxybenzene (resorcinol) and 1,2,4,5-benzenetetracarboxylic acid have been reported. The major interactions observed in the structures 1a–1e are N–H⋯O, N–H⋯S, O–H⋯O and C–H⋯O, in the form of homomeric and heteromeric patterns of the constituents, either as a single or cyclic hydrogen-bonded motifs. While in the adduct 1a, both homomeric and heteromeric units of both the constituents were observed, no heteromeric interactions were observed in 1b and 1c. In addition, in 1b, homomeric aggregation of molecules of 1 occurred in association with water molecules. However, while heteromeric interactions prevail between the constituents in 1d and 1e, only one of the co-crystallizing species gave homomeric interactions (4,4′-bipyridine N,N′-dioxide in 1d; 1,2,4,5-benzenetetracarboxylic acid in 1e). Further, in either type of the patterns, the cyclic motifs are formed as a pair-wise hydrogen bonds comprising of strong and weak hydrogen bonds (N–H⋯O/C–H⋯O or O–H⋯O/C–H⋯O). In three-dimensions, the ensembles of molecules yield planar sheets, ladders and pseudorotaxane type assemblies

• 256. Arslanov, Temirlan R.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Pressure control of magnetic clusters in strongly inhomogeneous ferromagnetic chalcopyrites2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, p. 7720-Article in journal (Refereed)

Room-temperature ferromagnetism in Mn-doped chalcopyrites is a desire aspect when applying those materials to spin electronics. However, dominance of high Curie-temperatures due to cluster formation or inhomogeneities limited their consideration. Here we report how an external perturbation such as applied hydrostatic pressure in CdGeP2:Mn induces a two serial magnetic transitions from ferromagnet to non-magnet state at room temperature. This effect is related to the unconventional properties of created MnP magnetic clusters within the host material. Such behavior is also discussed in connection with ab initio density functional calculations, where the structural properties of MnP indicate magnetic transitions as function of pressure as observed experimentally. Our results point out new ways to obtain controlled response of embedded magnetic clusters.

• 257. Arutyunov, Gleb
Integrability of the eta-deformed Neumann-Rosochatius model2017In: JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, ISSN 1751-8113, Vol. 50, no 3, article id 035401Article in journal (Refereed)

An integrable deformation of the well-known Neumann-Rosochatius system is studied by considering generalised bosonic spinning solutions on the eta-deformed AdS(5) x S-5 background. For this integrable model we construct a 4x4 Lax representation and a set of integrals of motion that ensures its Liouville integrability. These integrals of motion correspond to the deformed analogues of the Neumann-Rosochatius integrals and generalise the previously found integrals for the.-deformed Neumann and (AdS(5) x S-5)(eta) geodesic systems. Finally, we briefly comment on consistent truncations of this model.

• 258.
Univ Hamburg, Inst Theoret Phys, Luruper Chaussee 149, D-22761 Hamburg, Germany.;Univ Hamburg, Zentrum Math Phys, Bundesstr 55, D-20146 Hamburg, Germany.;Steklov Math Inst, Moscow, Russia..
Univ Hamburg, Inst Theoret Phys, Luruper Chaussee 149, D-22761 Hamburg, Germany.;Univ Hamburg, Zentrum Math Phys, Bundesstr 55, D-20146 Hamburg, Germany.. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. KTH Royal Inst Technol, NORDITA, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden.;Stockholm Univ, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
Superintegrability of geodesic motion on the sausage model2017In: Journal of Physics A: Mathematical and Theoretical, ISSN 1751-8113, E-ISSN 1751-8121, Vol. 50, no 24, article id 244002Article in journal (Refereed)

Reduction of the η-deformed sigma model on AdS5 x S5 to the two-dimensional squashed sphere (S2)η can be viewed as a special case of the Fateev sausage model where the coupling constant v is imaginary. We show that geodesic motion in this model is described by a certain superintegrable mechanical system with four-dimensional phase space. This is done by means of explicitly constructing three integrals of motion which satisfy the sl(2) Poisson algebra relations, albeit being non-polynomial in momenta. Further, we find a canonical transformation which transforms the Hamiltonian of this mechanical system to the one describing the geodesic motion on the usual two-sphere. By inverting this transformation we map geodesics on this auxiliary two-sphere back to the sausage model.

• 259. Arvanitidis, J.
High pressure study of the 2D polymeric phase of C60 by means of Raman spectroscopy2001In: High Pressure Research, ISSN 0895-7959, E-ISSN 1477-2299, Vol. 18, no 1-6, p. 145-151Article in journal (Refereed)

The effect of high hydrostatic pressure, up to 12GPa, on the intramolecular phonon frequencies and the material stability of the two-dimensional tetragonal Cm polymer has been studied by means of Raman spectroscopy in the spectral range of the radial intramolecular modes (200-800cm-1). A number of new Raman modes appear in the spectrum for pressures ≈ 1.4 and ≈ 5.0 GPa. The pressure coefficients for the majority of the phonon modes exhibit changes to lower values at P=4.0 GPa, which may be related to a structural modification of the 2D polymer to a more isotropic phase. The peculiarities observed in the Raman spectra are reversible and the material is stable in the pressure region investigated.

• 260. Arvanitidis, J.
Comparative Raman study of the 1D and 2D polymeric phases of C60 under pressure1999In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 215, no 1, p. 443-448Article in journal (Refereed)

The effect of symmetry lowering on the phonon spectra as well as the pressure effects on the vibrational spectrum of polymerized C60 were studied by Raman spectroscopy. Drastic changes related to the splitting of degenerate modes of the C60 molecule were observed together with selected softening of some of them. In spite of many similarities in the Raman spectra of the one- (1D) and two-dimensional (2D) polymeric forms of C60, some salient differences in the peak intensities and the appearance of complementary modes are evident. In the Raman spectrum of the 2D polymer under high pressure, new modes, which may be related to the deformations of molecular cages, appear. The observed pressure effects are reversible and the material remains stable for pressures up to 8.8 GPa.

• 261. Arvantidis, J.
Raman modes of the two-dimensional tetragonal polymeric phase of C60 under high pressure2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 114, no 20, p. 9099-9104Article in journal (Refereed)

The effect of high hydrostatic pressure, up to 12 GPa, on the phonon spectrum and the material stability of the two-dimensional (2D) tetragonal C60 polymer have been studied by means of Raman spectroscopy in the frequency range 100-2000 cm-1. A number of Raman modes appear in the spectrum for pressures above ~1.4 GPa, whose intensities increase with pressure. The pressure coefficients of the majority of the phonon modes change gradually to lower values for pressures around 4.0 GPa. The deformation of the C60 molecular cage along with the change of the material to a more isotropic state (as far as its elastic properties are concerned) resulting from the application of high pressure may be causing the observed effects in the Raman spectra. These effects are reversible upon pressure release and therefore the material is stable in the pressure region investigated.

• 262.
Luleå tekniska universitet.
Luleå tekniska universitet.
The NN-1, π and ΔN-1 delta decay modes in the nuclear medium1994In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 572, no 3-4, p. 600-620Article in journal (Refereed)

The dependence of the Δ-width on the Δ-decay channels is studied in the nuclear medium. We calculate the decay of the delta into a nucleon and a general pisobar mode consisting of NN-1-, π- and dN-1-modes. For the case of no width of the Δ in the pisobar we present partial contributions to the Δ-width from the Δ-decay channels: Δ→N+NN-1, Δ→N+π and Δ→N+ΔN-1. Results for a self-consistent treatment of the Δ-width in the pisobar is presented. The self-consistent treatment only modifies the results with no width in the pisobar to a small extent. It is found that NN-1 channel is not only dominating the decay at low energies of the Δ-resonance but at high densities (ρ>1.5ρ0) this channel also dominates the decay at higher energies. Qualitative agreement with inclusive and exclusive (p,n) and (3He,T) experiments is achieved

• 263.
Department of Psychology, Stockholm University.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Oy Keskuslaboratorio - Centrallaboratorium Ab. YKI Institute for Surface Chemistry. Oy Keskuslaboratorio - Centrallaboratorium Ab. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Department of Psychology, Stockholm University.
Haptic perception of fine surface texture: Psychophysical interpretation of the multidimensional spaceManuscript (preprint) (Other academic)
• 264.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
On the polarization of light reflected from beetle cuticle2017In: MATERIALS TODAY-PROCEEDINGS, ELSEVIER SCIENCE BV , 2017, Vol. 4, no 4, p. 4933-4941Conference paper (Refereed)

The use of Mueller matrices for studies of polarizing properties and cuticle structure of scarab beetles are partly reviewed. Specifically we show how the polarization of the reflected light can be quantified in terms of degree of polarization and ellipticity. It is also shown that sum decomposition of Mueller matrices reveals cuticle reflection characteristics in different spectral regions, e.g. in terms of mirrors and circular polarizers. With a differential decomposition of cuticle transmission Mueller matrices, we determine the spectral variation in the fundamental optical properties circular birefringence and dichroism. (C) 2017 Elsevier Ltd. All rights reserved.

• 265.
Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering. CNRS 91128 Palaiseau, France. CNRS 91128 Palaiseau, FranceCNRS 91128 Palaiseau, France. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering. CNRS 91128 Palaiseau, France.
Sum decomposition of Mueller matrices from beetle cuticles2015Conference paper (Other academic)

Spectral Mueller matrices are very rich in information about physical properties of a sample. We have recently shown that polarizing properties like ellipticity and degree of polarization can be extracted from a Mueller matrix measured on a beetle cuticle (exoskeleton). Mueller matrices can also be used in regression analysis to model nanostructures in cuticles. Here we present the use of sum decomposition of Mueller matrices from these depolarizing biological reflectors to explore the fundamental character of these reflectors. The objective is to decompose a Mueller matrix into well- defined ideal non-depolarizing matrices corresponding to mirrors, circular polarizers, halfwave retarders etc.Generally it is possible to decompose a measured depolarizing Mueller matrix M into four (or fewer) non-depolarizing matrices according to M=λ1M1+λ2M2+λ3M3+λ4M4, where λ1, λ2, λ3 and λ4 are eigenvalues of the covariance matrix of M. Two strategies for decomposition will be discussed. A Cloude decomposition will provide the eigenvalues and also the Mi’s although the latter will contain severe noise in some spectral regions. However, a major advantage with the Cloude decomposition is that the number of nonzero eigenvalues is directly obtained, i.e. the number of contributing Mi matrices. In an alternative decomposition, the Mi’s are assumed and the eigenvalues are found by regression analysis based on M. In the case with two non-zero eigenvalues we define a model Mueller matrix MD=αRM1+βRM2 with αR+βR=1. With αR as adjustable parameter, the Frobenius norm ||M-MD|| is minimized for each wavelength in the spectral range of M. For more complex structures, the regression can be extended by adding more matrices up to a total of four. Advantages with a regression approach are its simplicity and stability compared to a Cloude decomposition.Mueller-matrix spectra of beetle cuticles are recorded with a dual rotating compensator ellipsometer in the spectral range 400 – 900 nm at angles of incidence in the range 20 - 75°. The application of decomposition on biological reflectors is demonstrated on M measured on the beetle Cetonia aurata, which represents a narrow-band chiral Bragg reflector with two non-zero eigenvalues. A decomposition in an ideal mirror and a circular polarizer is feasible. In another example, the broad-band and gold-colored beetle Chrysina argenteola, we show that more than two eigenvalues can be nonzero, especially at oblique incidence, and additional matrices are involved.

• 266.
Umeå University, Faculty of Science and Technology, Department of Physics.
Functional and Flexible Light-Emitting Electrochemical Cells2015Doctoral thesis, comprehensive summary (Other academic)

The introduction of artificial illumination has brought extensive benefits to mankind, and during the last years we have seen a tremendous progress in this field with the introduction of the energy-efficient light-emitting diode (LED) and the high-contrast organic LED display. These high-end technologies are, however, produced using costly and complex processes, and it is anticipated that the next big thing in the field will be the advent of a low-cost and “green” illumination technology, which can be fabricated in a cost- and material-efficient manner using non-toxic and abundant raw materials, and which features attractive form factors such as flexibility, robustness and light-weight. The light-emitting electrochemical cell (LEC) is a newly invented illumination technology, and in this thesis we present results that imply that it can turn the above vision into reality.

The thin-film LEC comprises an active material sandwiched between a cathode and an anode as its key constituent parts. With the aid of a handheld air-brush, we show that functional large-area LECs can be fabricated by simply spraying three layers of solution -- forming the anode, active material, and cathode -- on top of a substrate. We also demonstrate that such “spray-sintered” LECs can feature multicolored emission patterns, and be fabricated directly on complex-shaped surfaces, with one notable example being the realization of a light-emission fork!

Almost all LECs up-to-date have been fabricated on glass substrates, but for a flexible and light-weight emissive device, it is obviously relevant to identify more appropriate substrate materials. For this end, we show that it is possible to spray-coat the entire LEC directly on conventional copy paper, and that such paper-LECs feature uniform light-emission even under heavy bending and flexing.

We have further looked into the fundamental aspects of the LEC operation and demonstrated that the in-situ doping formation, which is a characteristic and heralded feature of LECs, can bring problems in the form of doping-induced self-absorption. By quantitatively analyzing this phenomenon, we provided straightforward guidelines on how future efficiency-optimized LEC devices should be designed.

The in-situ doping formation process brings the important advantage that LECs can be fabricated from solely air-stabile materials, but during light emission the device needs to be protected from the ambient air. We have therefore developed a functional glass/epoxy encapsulation procedure for the attainment of LEC devices that feature a record-long ambient-air operational lifetime of 5600 h. For the light-emission device of the future, it is however critical that the encapsulation is flexible, and in our last study, we show that the use of multi-layer barrier can result in high-performance flexible LECs.

• 267.
Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC, Umeå, Sweden.
Umeå University, Faculty of Science and Technology, Department of Physics. Umeå University, Faculty of Science and Technology, Department of Physics.
Light-Emitting Paper2015In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 25, no 21, p. 3238-3245Article in journal (Refereed)

A solution-based fabrication of flexible and light-weight light-emitting devices on paper substrates is reported. Two different types of paper substrates are coated with a surface-emitting light-emitting electrochemical cell (LEC) device: a multilayer-coated specialty paper with an intermediate surface roughness of 0.4 μm and a low-end and low-cost copy paper with a large surface roughness of 5 μm. The entire device fabrication is executed using a handheld airbrush, and it is notable that all of the constituent layers are deposited from solution under ambient air. The top-emitting paper-LECs are highly flexible, and display a uniform light emission with a luminance of 200 cd m−2 at a current conversion efficacy of 1.4 cd A−1.

• 268. Asano, Masanari
Linnaeus University, Faculty of Technology, Department of Mathematics.
Quantum Information Biology2016In: Contextuality from Quantum Physics to Psychology / [ed] Ehtibar Dzhafarov, Scott Jordan, Ru Zhang, Victor Cervantes, World Scientific, 2016, p. 399-413Chapter in book (Refereed)

This chapter reviews quantum(-like) information biology (QIB). Here biology is treated widely as even covering cognition and its derivatives: psychology and decision making, sociology, and behavioral economics and finances. QIB provides an integrative description of information processing by bio-systems at all scales of life: from proteins and cells to cognition, ecological and social systems. Mathematically QIB is based on the theory of adaptive quantum systems (which covers also open quantum systems). Ideologically QIB is based on the quantum-like (QL) paradigm: complex bio-systems process information in accordance with the laws of quantum information and probability. This paradigm is supported by plenty of statistical bio-data collected at all bio-scales. QIB reflects the two fundamental principles: a) adaptivity; and, b) openness (bio-systems are fundamentally open). In addition, quantum adaptive dynamics provides the most generally possible mathematical representation of these principles.

• 269.
University of Bayreuth, Germany.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. University of Bayreuth, Germany.
Challenges for semilocal density functionals with asymptotically nonvanishing potentials2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 7, article id 075140Article in journal (Refereed)

The Becke-Johnson model potential [A. D. Becke and E. R. Johnson, J. Chem. Phys. 124, 221101 ( 2006)] and the potential of the AK13 functional [R. Armiento and S. Kummel, Phys. Rev. Lett. 111, 036402 ( 2013)] have been shown to mimic features of the exact Kohn-Sham exchange potential, such as step structures that are associated with shell closings and particle-number changes. A key element in the construction of these functionals is that the potential has a limiting value far outside a finite system that is a system-dependent constant rather than zero. We discuss a set of anomalous features in these functionals that are closely connected to the nonvanishing asymptotic potential. The findings constitute a formidable challenge for the future development of semilocal functionals based on the concept of a nonvanishing asymptotic constant.

KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
Hemispherical anomaly from asymmetric initial states2016In: PHYSICAL REVIEW D, ISSN 2470-0010, Vol. 94, no 4, article id 043009Article in journal (Refereed)

We investigate if the hemispherical asymmetry in the CMB is produced from "asymmetric" excited initial conditions. We show that in the limit where the deviations from the Bunch-Davies vacuum are large and the scale of new physics is maximally separated from the inflationary Hubble parameter, the primordial power spectrum is modulated only by position-dependent dipole and quadrupole terms. Requiring the dipole contribution in the power spectrum to account for the observed power asymmetry, A = 0.07 +/- 0.022, we show that the amount of quadrupole terms is roughly equal to A(2). The mean local bispectrum, which gets enhanced for the excited initial state, is within the 1 sigma bound of Planck 2015 results for a large field model, f(NL) similar or equal to 4.17, but is reachable by future CMB experiments. The amplitude of the local non-Gaussianity modulates around this mean value, depending on the angle that the correlated patches on the 2d CMB surface make with the preferred direction. The amount of variation is minimized for the configuration in which the short and long wavelength modes are around the preferred pole and vertical bar(k(3)) over right arrow vertical bar approximate to vertical bar(k) over right arrow (l approximate to 10)vertical bar << vertical bar(k(1)) over right arrow vertical bar approximate to vertical bar(k(2)) over right arrow vertical bar approximate to vertical bar(k) over right arrow (l approximate to 2500)vertical bar with f(NL)(min) approximate to 3.64. The maximum occurs when these modes are at the antipode of the preferred pole, f(NL)(max) approximate to 4.81. The difference of non-Gaussianity between these two configurations is as large as similar or equal to 1.17, which can be used to distinguish this scenario from other scenarios that try to explain the observed hemispherical asymmetry.

• 271.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
Effects of disorder in metallic systems from First-Principles calculations2010Doctoral thesis, comprehensive summary (Other academic)

In this thesis, quantum-mechanical calculations within density-functional theory on metallic systems are presented. The overarching goal has been to investigate effects of disorder. In particular, one of the properties investigated is the bindingenergy shifts for core electrons in binary alloys using different theoretical methods. These methods are compared with each other and with experimental results. One such method, the so-called Slater-Janak transition state method relies on the assumption that the single-particle eigenvalues within density-functional theory are linear functions of their respective occupation number. This assumption is investigated and it is found that while the eigenvalues to a first approximation show linear behavior, there are also nonlinearities which can influence the core-level binding energy shifts.

Another area of investigation has been iron based alloys at pressures corresponding to those in the Earth’s inner core. This has been done for the hexagonal close packed and face entered cubic structures. The effects of alloying iron with magnesium and nickel on the equation of state as well on the elastic properties have been investigated. The calculations have shown that the hexagonal close packed structure in FeNi is more isotropic than the face-centered cubic structure, and that adding Mg to Fe has a large impact on the elastic properties.

Finally, the effects of disorder due to thermal motion of the atoms have been investigated through ab-initio molecular dynamics simulations. Within the limits of this method and the setup, it is found that the face-centered cubic structure of molybdenum can be dynamically stabilized at high temperature, leading to a metastable structure, on the average. The dynamical stabilization of face-centered cubic molybdenum also rendered it possible to accurately calculate the lattice stability relative to the body-centered cubic phase. Inclusion of temperature effects for the lattice stability using ab-initio molecular dynamics simulations resolves the disagreement between ab-initio calculations and thermochemical methods.

• 272. Aslak, Ulf
Umeå University, Faculty of Science and Technology, Department of Physics.
Constrained information flows in temporal networks reveal intermittent communities2018In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 97, no 6, article id 062312Article in journal (Refereed)

Many real-world networks represent dynamic systems with interactions that change over time, often in uncoordinated ways and at irregular intervals. For example, university students connect in intermittent groups that repeatedly form and dissolve based on multiple factors, including their lectures, interests, and friends. Such dynamic systems can be represented as multilayer networkswhere each layer represents a snapshot of the temporal network. In this representation, it is crucial that the links between layers accurately capture real dependencies between those layers. Often, however, these dependencies are unknown. Therefore, current methods connect layers based on simplistic assumptions that do not capture node-level layer dependencies. For example, connecting every node to itself in other layers with the same weight can wipe out dependencies between intermittent groups, making it difficult or even impossible to identify them. In this paper, we present a principled approach to estimating node-level layer dependencies based on the network structure within each layer. We implement our node-level coupling method in the community detection framework Infomap and demonstrate its performance compared to current methods on synthetic and real temporal networks. We show that our approach more effectively constrains information inside multilayer communities so that Infomap can better recover planted groups in multilayer benchmark networks that represent multiple modeswith different groups and better identify intermittent communities in real temporal contact networks. These results suggest that node-level layer coupling can improve the modeling of information spreading in temporal networks and better capture intermittent community structure.

• 273.
Universit́e de Haute Alsace, France .
Universit́e de Haute Alsace, France . Lund University.
Generalization of n-ary Nambu algebras and beyond2009In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 50, no 8, p. Article number 083501-Article in journal (Refereed)

The aim of this paper is to introduce n-ary Hom-algebra structures generalizing the n-ary algebras of Lie type including n-ary Nambu algebras, n-ary Nambu-Lie algebras and n-ary Lie algebras, and n-ary algebras of associative type including n-ary totally associative and n-ary partially associative algebras. We provide examples of the new structures and present some properties and construction theorems. We describe the general method allowing one to obtain an n-ary Hom-algebra structure starting from an n-ary algebra and an n-ary algebra endomorphism. Several examples are derived using this process. Also we initiate investigation of classification problems for algebraic structures introduced in the article and describe all ternary three-dimensional Hom-Nambu-Lie structures with diagonal homomorphism.

• 274.
KTH, School of Engineering Sciences (SCI), Theoretical Physics.
A kernel function approach to exact solutions of Calogero-Moser-Sutherland type models2016Doctoral thesis, comprehensive summary (Other academic)

This Doctoral thesis gives an introduction to the concept of kernel functionsand their signicance in the theory of special functions. Of particularinterest is the use of kernel function methods for constructing exact solutionsof Schrodinger type equations, in one spatial dimension, with interactions governedby elliptic functions. The method is applicable to a large class of exactlysolvable systems of Calogero-Moser-Sutherland type, as well as integrable generalizationsthereof. It is known that the Schrodinger operators with ellipticpotentials have special limiting cases with exact eigenfunctions given by orthogonalpolynomials. These special cases are discussed in greater detail inorder to explain the kernel function methods with particular focus on the Jacobipolynomials and Jack polynomials.

• 275.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
Integral representation of solution to the non-stationary Lamé equationManuscript (preprint) (Other academic)

We consider methods for constructing explicit solutions of the non-stationary Lame equation,which is a generalization of the classical Lame equation, that has appeared in works on integrablemodels, conformal eld theory, high energy physics and representation theory. We also present ageneral method for constructing integral representations of solutions to the non-stationary Lameequation by a recursive scheme. Explicit integral representations, for special values of the modelparameters, are also presented. Our approach is based on kernel function methods which can benaturally generalized to the non-stationary Heun equation.

• 276.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
Source Identities and Kernel Functions for Deformed (Quantum) Ruijsenaars Models2014In: Letters in Mathematical Physics, ISSN 0377-9017, E-ISSN 1573-0530, Vol. 104, no 7, p. 811-835Article in journal (Refereed)

We consider the relativistic generalization of the quantum A (N-1) Calogero-Sutherland models due to Ruijsenaars, comprising the rational, hyperbolic, trigonometric and elliptic cases. For each of these cases, we find an exact common eigenfunction for a generalization of Ruijsenaars analytic difference operators that gives, as special cases, many different kernel functions; in particular, we find kernel functions for Chalykh-Feigin-Veselov-Sergeev-type deformations of such difference operators which generalize known kernel functions for the Ruijsenaars models. We also discuss possible applications of our results.

• 277.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
Series solutions of the non-stationary Heun equationManuscript (preprint) (Other academic)

We consider the non-stationary Heun equation, also known as quantum PainlevéVI, which has appeared in dierent works on quantum integrable models and conformaleld theory. We use a generalized kernel function identity to transform the problemto solve this equation into a dierential-dierence equation which, as we show, canbe solved by ecient recursive algorithms. We thus obtain series representations ofsolutions which provide elliptic generalizations of the Jacobi polynomials. These seriesreproduces, in a limiting case, a perturbative solution of the Heun equation due toTakemura, but our method is dierent in that we expand in non-conventional basisfunctions that allow us to obtain explicit formulas to all orders;

• 278. Aubin, G.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
Highly dispersive photonic crystal-based guiding structures2006In: CLEO/QELS 2006, Optical Society of America, 2006, p. 972-974Conference paper (Refereed)

Propagating modes supported by Photonic-Crystal guiding structures can demonstrate very high group velocity dispersion close to a cut-off. We investigate here the wavelength dependence of the dispersion for different Photonic Crystal structures.

• 279.
KTH, School of Computer Science and Communication (CSC), Computational Biology, CB.
The physics of distributed information systems2013In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 473, no 1, p. 012017-Article in journal (Refereed)

This paper aims to introduce Distributed Systems as a field where the ideas and methods of physics can potentially be applied, and to provide entry points to a wide literature. The contributions of Leslie Lamport, inspired by Relativity Theory, and of Edsger Dijkstra, which has the flavor of a growth process, are discussed at some length. The intent of the author is primarily to stimulate interest in the statistical physics community, and the discussions are therefore framed in a non-technical language; the author apologizes in advance to readers from the computer science side for the unavoidable impreciseness and ambiguities.

• 280.
Division of Structural Mechanics, Lund Institute of Technology.
Kari, LeifKTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
Constitutive Models for Rubber IV: proceedings of the 4th European Conference for Constitutive Models for Rubber, ECCMR 2005, Stockholm, Sweden, 27-29 June 20052005Collection (editor) (Refereed)

The unique properties of elastomeric materials are taken advantage of in many engineering applications. Elastomeric units are used as couplings or mountings between stiff parts. Examples are shock absorbers, vibration insulators, flexible joints, seals and suspensions etc.

However, the complicated nature of the material behavior makes it difficult to accurately predict the performance of these units, using for example finite element modelling. It is therefore necessary that the constitutive model accurately capture relevant aspects of the mechanical behavior.

The latest development concerning constitutive modelling of rubber is collected in these proceedings. It is the fourth ECCMR-European Conference on Constitutive Modelling in a series on this subject.

Topics included in this volume are, Hyperelastic models, Strength, fracture & fatigue, Dynamic properties & the Fletcher-Gent effect, Micro-mechanical & statistical approaches, Stress softening, Viscoelasticity, Filler reinforcement, and Tyres, fiber & cord reinforced rubber.

• 281.
Department of Physics and I3N, University of Aveiro, Aveiro, Portugal.
Institute of Mathematical Problems of Biology, Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, 142290 Moscow Region, Russian Federation. Department of Physics and I3N, University of Aveiro, Aveiro, Portugal. Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Institute of Mathematical Problems of Biology, Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, 142290 Moscow Region, Russian Federation. Physics Faculty, Southern Federal University, Rostov-on-Don 344090, Russian Federation.
Optoelectronics and defect levels in hydroxyapatite by first-principles2018In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 148, no 15, article id 154706Article in journal (Refereed)

Hydroxyapatite (HAp) is an important component of mammal bones and teeth, being widely used in prosthetic implants. Despite the importance of HAp in medicine, several promising applications involving this material (e.g., in photo-catalysis) depend on how well we understand its fundamental properties. Among the ones that are either unknown or not known accurately, we have the electronic band structure and all that relates to it, including the bandgap width. We employ state-of-the-art methodologies, including density hybrid-functional theory and many-body perturbation theory within the dynamically screened single-particle Green's function approximation, to look at the optoelectronic properties of HAp. These methods are also applied to the calculation of defect levels. We find that the use of a mix of (semi-)local and exact exchange in the exchange-correlation functional brings a drastic improvement to the band structure. Important side effects include improvements in the description of dielectric and optical properties not only involving conduction band (excited) states but also the valence. We find that the highly dispersive conduction band bottom of HAp originates from anti-bonding σ* states along the ⋯OH-OH-⋯ infinite chain, suggesting the formation of a conductive 1D-ice phase. The choice of the exchange-correlation treatment to the calculation of defect levels was also investigated by using the OH-vacancy as a testing model. We find that donor and acceptor transitions obtained within semi-local density functional theory (DFT) differ from those of hybrid-DFT by almost 2 eV. Such a large discrepancy emphasizes the importance of using a high-quality description of the electron-electron interactions in the calculation of electronic and optical transitions of defects in HAp.

• 282. Axelsson, O.
Reactive evaporation of potassium in CO2 and the formation of bulk intermediates1994In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 12, no 1, p. 158-160Article in journal (Refereed)

Potassium vapor condensed in CO2 has been studied by transmission infrared spectroscopy and by total pressure thermal desorption spectroscopy. The results are compared with surface spectroscopic data for CO2 adsorbed on alkali metal overlayers. Both systems show the formation of bulk coordinated oxalate species at cryogenic temperatures and the conversion to carbonate intermediates upon annealing.

• 283. Axelsson, O.
A theoretical and experimental study of reaction pathways for the interaction of CO2 with alkali-modified surfaces1995In: Journal of Physical Chemistry, ISSN 0022-3654, Vol. 99, no 18, p. 7028-7035Article in journal (Refereed)
• 284.
Turkish Atomic Energy Authority, Ankara Nuclear Research and Training Center.
Turkish Atomic Energy Authority, Ankara Nuclear Research and Training Center. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.

The aim of the study is to reduce the environmental impact of ash deposits. Ash from coal and biomass combustion, containing uranium and thorium from Yatagan-Silopi and Tuncbilek coal; cesium-137 from forests in northeastern Turkey and central Sweden. Turkey is dependent on coal for power generation and huge volumes of ash (>15 Mton/yr) are produced every year. Because of that certain coals, in particular Yatagan, with known problems from Mo and U leaching to the ground water, and Silopi oil shales/asphaltites were studied. Biomass ash comes from branches, bark and other unused parts of the trees and plants. This ash has low concentration of environmentally hazardous metals, but {sup 137}Cs is a problem in certain regions and it is of interest to investigate the possibilities to leach this metal from the ash. Washing ash through rapid chemical leaching at low pH reduces the slow release of metals from ash due to precipitation and besides it may lead to metal recovery from the ash. Initial experiments were done in batch form, in which the neutralizing capacity at pH 1-1.5 was measured by adding sulfuric acid to maintain pH for mixtures of ash and water. Subsequent experiments were done in bench scale. The process also reduced the metal content of the ash, due to chemical leaching of metal oxides and ion exchange at the surfaces of stable oxides. This means that treated ash will not release further metals and, eventually, relaxes the requirements on depositories and allows the ash from coal to be used as an admixture in cement, and to be used as a fertilizer following after treatment of ash from biomass

• 285.
Univ Oslo, Dept Phys, Ctr Mat Sci & Nanotechnol, POB 1048, N-0316 Oslo, Norway.;Natl Ctr Nucl Res, A Soltana 7, PL-05400 Otwock, Poland..
Univ Oslo, Dept Phys, Ctr Mat Sci & Nanotechnol, POB 1048, N-0316 Oslo, Norway.. Univ Oslo, Dept Phys, Ctr Mat Sci & Nanotechnol, POB 1048, N-0316 Oslo, Norway.. KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Integrated devices and circuits. Univ Oslo, Dept Phys, Ctr Mat Sci & Nanotechnol, POB 1048, N-0316 Oslo, Norway.. Univ Oslo, Dept Phys, Ctr Mat Sci & Nanotechnol, POB 1048, N-0316 Oslo, Norway..
Defect annealing kinetics in ZnO implanted with Zn substituting elements: Zn interstitials and Li redistribution2019In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, no 7, article id 075703Article in journal (Refereed)

It is known that the behavior of residual Li in ion implanted ZnO depends on the preferential localization of the implants, in particular, forming characteristic Li depleted or Li pile-up regions for Zn or O sublattice occupation of the implants due to the corresponding excess generation of Zn and O interstitials in accordance with the so-called "+1 model." However, the present study reveals that conditions for the radiation damage annealing introduce additional complexity into the interpretation of the Li redistribution trends. Specifically, four implants residing predominantly in the Zn-sublattice, but exhibiting different lattice recovery routes, were considered. Analyzing Li redistribution trends in these samples, it is clearly shown that Li behavior depends on the defect annealing kinetics which is a strong function of the implanted fluence and ion species. Thus, Li depleted and Li pile-up regions (or even combinations of the two) were observed and correlated with the defect evolution in the samples. It is discussed how the observed Li redistribution trends can be used for better understanding a thermal evolution of point defects in ZnO and, in particular, energetics and migration properties of Zn interstitials.

• 286.
Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
Quantum Holonomy for Many-Body Systems and Quantum Computation2013Doctoral thesis, comprehensive summary (Other academic)

The research of this Ph. D. thesis is in the field of Quantum Computation and Quantum

Information. A key problem in this field is the fragile nature of quantum states. This

becomes increasingly acute when the number of quantum bits (qubits) grows in order to

perform large quantum computations. It has been proposed that geometric (Berry) phases

may be a useful tool to overcome this problem, because of the inherent robustness of such

phases to random noise. In the thesis we investigate geometric phases and quantum

holonomies (matrix-valued geometric phases) in many-body quantum systems, and elucidate

the relationship between these phases and the quantum correlations present in the systems.

An overall goal of the project is to assess the feasibility of using geometric phases and

quantum holonomies to build robust quantum gates, and investigate their behavior when the

size of a quantum system grows, thereby gaining insights into large-scale quantum

computation.

In a first project we study the Uhlmann holonomy of quantum states for hydrogen-like

atoms. We try to get into a physical interpretation of this geometric concept by analyzing its

relation with quantum correlations in the system, as well as by comparing it with different

types of geometric phases such as the standard pure state geometric phase, Wilczek-Zee

holonomy, Lévay geometric phase and mixed-state geometric phases. In a second project we

establish a unifying connection between the geometric phase and the geometric measure of

entanglement in a generic many-body system, which provides a universal approach to the

study of quantum critical phenomena. This approach can be tested experimentally in an

interferometry setup, where the geometric measure of entanglement yields the visibility of

the interference fringes, whereas the geometric phase describes the phase shifts. In a third

project we propose a scheme to implement universal non-adiabatic holonomic quantum

gates, which can be realized in novel nano-engineered systems such as quantum dots,

molecular magnets, optical lattices and topological insulators. In a fourth project we propose

an experimentally feasible approach based on “orange slice” shaped paths to realize non-

Abelian geometric phases, which can be used particularly for geometric manipulation of

qubits. Finally, we provide a physical setting for realizing non-Abelian off-diagonal

geometric phases. The proposed setting can be implemented in a cyclic chain of four qubits

with controllable nearest-neighbor interactions. Our proposal seems to be within reach in

various nano-engineered systems and therefore opens up for first experimental test of the

non-Abelian off-diagonal geometric phase.

• 287.
University of Isfahan, Iran.
Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Uppsala University.
Spin-electric Berry phase shift in triangular molecular magnets2016In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 23, article id 235423Article in journal (Refereed)

We propose a Berry phase effect on the chiral degrees of freedom of a triangular magnetic molecule. The phase is induced by adiabatically varying an external electric field in the plane of the molecule via a spin-electric coupling mechanism present in these frustrated magnetic molecules. The Berry phase effect depends on spin-orbit interaction splitting and on the electric dipole moment. By varying the amplitude of the applied electric field, the Berry phase difference between the two spin states can take any arbitrary value between zero and Ï, which can be measured as a phase shift between the two chiral states by using spin-echo techniques. Our result can be used to realize an electric-field-induced geometric phase-shift gate acting on a chiral qubit encoded in the ground-state manifold of the triangular magnetic molecule.

• 288.
Stockholm University, Faculty of Science, Department of Physics.
Creation and Detection of Single Photons2016Doctoral thesis, comprehensive summary (Other academic)

A growing number of technologies employ quantum properties in order to produce solutions that surpass the performance of conventional devices, or to execute operations that are fundamentally impossible with classical systems alone. In the field of optical quantum information science, photons are utilized to encode, communicate and manipulate information, making them vitally important. While photon production always constitutes the first step in any optical experiment, in the field of quantum information science, the recording of data through the process of photon detection is an equally crucial final step.

This thesis deals with both the single photons generation (based on diamond color defects) and their detection, utilizing a novel type of superconducting detectors. In particular, part one of this thesis is devoted to the construction of custom designed microscope setup, and the development of laboratory experiments, to enable the generation of single photons as well as the investigation of the optical and spin properties of diamond color centers. Confocal microscopy is used for this purpose, as it allows for the identification and addressing of individual color centers that emit only single photons. This microscope also feature an integrated self-built microwave and magnetic hardware setup, which allows for a wide range of spin environment spectroscopy studies. Single photon emission is demonstrated through both photon anti-bunching and Rabi oscillations at room temperature.

The second part of the thesis offers an exploration of superconducting single photon detectors through experiment. Since electronics are an essential part of these detectors, the possibility of using a novel alternative scheme based on capacitive readout combined with fast gating to enable simplified readout is demonstrated. This scheme overcomes the limitations of conventional readout schemes, which require large bandwidth amplification and complex counting electronics. Besides photon detection, the capabilities of these detectors are also expanded to include high-energy particles in the MeV energy range, and the detectors are demonstrated to not only detect single α- and β-particles, but to do so with near unity efficiency. Finally, a multipurpose testing station for superconducting detectors is demonstrated with a central objective of optimizing the coupling efficiency of light to the active area of the detector, as well as to allow for a fast exchange of the optical fiber, thereby facilitating an efficient characterization of the detector. The optimization of this coupling efficiency was demonstrated through proof-of-principle experiments.

• 289.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Nuclear and Particle Physics.
Department of Physics and Astronomy.
Hard and soft QCD in charmonium production2000Conference paper (Other scientific)

We show that both hard perturbative and soft non-perturbative QCD effects are important in hadroproduction of charmonium. Observed $x_F$ and $p_\perp$ distributions of J/psi in fixed target experiments can be well described by our Monte Carlo model based

• 290.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics. KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
Type-1.5 superconductivity in multiband systems: Magnetic response, broken symmetries and microscopic theory - A brief overview2012In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 479, p. 2-14Article in journal (Refereed)

A conventional superconductor is described by a single complex order parameter field which has two fundamental length scales, the magnetic field penetration depth lambda and the coherence length xi. Their ratio kappa determines the response of a superconductor to an external field, sorting them into two categories as follows; type-I when kappa < 1/root 2 and type-II when kappa > 1/root 2. We overview here multicomponent systems which can possess three or more fundamental length scales and allow a separate "type-1.5" superconducting state when, e. g. in two-component case xi(1) < root 2 lambda < xi(2). In that state, as a consequence of the extra fundamental length scale, vortices attract one another at long range but repel at shorter ranges. As a consequence the system should form an additional Semi-Meissner state which properties we discuss below. In that state vortices form clusters in low magnetic fields. Inside the cluster one of the component is depleted and the superconductor-to-normal interface has negative energy. In contrast the current in second component is mostly concentrated on the cluster's boundary, making the energy of this interface positive. Here we briefly overview recent developments in Ginzburg-Landau and microscopic descriptions of this state.

• 291.
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
Rotational response of superconductors: Magnetorotational isomorphism and rotation-induced vortex lattice2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 10, p. 104501-Article in journal (Refereed)

The analysis of nonclassical rotational response of superfluids and superconductors was performed by Onsager [Onsager, Nuovo Cimento, Suppl. 6, 279 (1949)] and London [Superfluids (Wiley, NewYork, 1950)] and crucially advanced by Feynman [Prog. Low Temp. Phys. 1, 17 (1955)]. It was established that, in the thermodynamic limit, neutral superfluids rotate by forming-without any threshold-a vortex lattice. In contrast, the rotation of superconductors at angular frequency Omega-supported by uniform magnetic field B-L proportional to Omega due to surface currents-is of the rigid-body type (London law). Here we show that, neglecting the centrifugal effects, the behavior of a rotating superconductor is identical to that of a superconductor placed in a uniform fictitious external magnetic field (H) over tilde = -B-L. In particular, the isomorphism immediately implies the existence of two critical rotational frequencies in type-2 superconductors.

• 292. Babkevich, P.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. Ecole Polytech Fed Lausanne, ICMP, Lab Quantum Magnetism, Switzerland.
Dimensional Reduction in Quantum Dipolar Antiferromagnets2016In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 116, no 19, article id 197202Article in journal (Refereed)

We report ac susceptibility, specific heat, and neutron scattering measurements on a dipolar-coupled antiferromagnet LiYbF4. For the thermal transition, the order-parameter critical exponent is found to be 0.20(1) and the specific-heat critical exponent -0.25(1). The exponents agree with the 2D XY/h(4) universality class despite the lack of apparent two-dimensionality in the structure. The order-parameter exponent for the quantum phase transitions is found to be 0.35(1) corresponding to (2 + 1)D. These results are in line with those found for LiErF4 which has the same crystal structure, but largely different T-N, crystal field environment and hyperfine interactions. Our results therefore experimentally establish that the dimensional reduction is universal to quantum dipolar antiferromagnets on a distorted diamond lattice.

• 293.
Mainz University, Department of Mathematics.
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.). KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
Dynamical Symmetries in Supersymmetric Matrix2008In: Documenta Mathematica, ISSN 1431-0635, E-ISSN 1431-0643, Vol. 13, p. 103-116Article in journal (Refereed)

We reveal a dynamical SU(2) symmetry in the asymptotic description of supersymmetric matrix models. We also consider a recursive approach for determining the ground state, and point out some additional properties of the model(s).

• 294.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Analytical Design and Optimization of a WR-3 Waveguide Diplexer Synthesized using Direct Coupled Resonator Cavities2017Report (Other academic)

A WR-3 coupled waveguide resonator diplexer is designed, analytically, using the insertion loss method, and subsequently simulated and optimized in HFSS. The design features ten iris coupled resonator cavities, assembled with a power divider in a T-junction topology. The diplexer channel filters yield a 5th order Chebyshev type frequency response, centered around 265 GHz and 300 GHz, respectivley. The resulting diplexer channels have bandwidths of 13 GHz and 11.6 GHz, respectivley, and a maximum passband return loss of -6.35 dB for channel A and -6.95 dB for channel B. A usable diplexer should have a passband return loss of at most -20 dB. Further optimization or, alternatively, changing the features of the design is needed to reduce the passband ripple to a level for which the diplexer is usable in practice. Possible improvements can be made by making the channel passbands narrower or, alternatively, increasing the number of resonators in the channel filters.

• 295.
Linköping University, The Department of Physics, Chemistry and Biology.
Future Upgrades of the LHC Beam Screen Cooling System2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis

The topic of this thesis concerns the LHC, the next large particle accelerator at CERN which will start operating in 2007. Being based on superconductivity, the LHC needs to operate at very low temperatures, which makes great demands on the cryogenic system of the accelerator. To cope with the heat loads induced by the particle beam, a beam screen cooled with forced flow of supercritical helium is used.

There is an interest in upgrading the energy and luminosity of the LHC in the future and this would require a higher heat load to be extracted by the beam screen cooling system. The objective of this thesis is to quantify different ways to upgrade this system by mainly studying the effects of different pressure and temperatures levels as well as a different cooling medium, neon.

For this a numerical program which simulates one-dimensional pipe flow was constructed. The frictional forces were accounted for by the empirical concept of friction factor. For the fluid properties, software using empirically made correlations was used. To validate the numerical program, a comparison with previous experimental work was done. The agreement with experimental data was good for certain flow configurations, worse for others. From this it was concluded that further comparisons with experimental data must be made in order to tell the accuracy of the mathematical model and the correlations for fluid properties used.

When using supercritical helium, thermo-hydraulic instabilities may arise in the cooling loop. It was of special interest to see how well a numerical program could simulate and predict this phenomenon. It was found that the numerical program did not function for such unstable conditions; in fact it was much more sensitive than what reality is.

For the beam screen cooling system we conclude that to cope with the increased heat loads of future upgrades, an increase in pressure level is needed regardless if the coolant remains helium, or is changed to neon. Increasing the pressure level also makes that the problems with thermo-hydraulic instabilities can be avoided. Of the two coolants, helium gave the best heat extraction capacity. Unlike neon, it is also possible to keep the present temperature level when using helium.

• 296. Bae, Seung-Hee
Umeå University, Faculty of Science and Technology, Department of Physics.
Scalable and Efficient Flow-Based Community Detection for Large-Scale Graph Analysis2017In: ACM Transactions on Knowledge Discovery from Data, ISSN 1556-4681, E-ISSN 1556-472X, Vol. 11, no 3, article id 32Article in journal (Refereed)

Community detection is an increasingly popular approach to uncover important structures in large networks. Flow-based community detection methods rely on communication patterns of the network rather than structural properties to determine communities. The Infomap algorithm in particular optimizes a novel objective function called the map equation and has been shown to outperform other approaches in third-party benchmarks. However, Infomap and its variants are inherently sequential, limiting their use for large-scale graphs. In this article, we propose a novel algorithm to optimize the map equation called RelaxMap. RelaxMap provides two important improvements over Infomap: parallelization, so that the map equation can be optimized over much larger graphs, and prioritization, so that the most important work occurs first, iterations take less time, and the algorithm converges faster. We implement these techniques using OpenMP on shared-memory multicore systems, and evaluate our approach on a variety of graphs from standard graph clustering benchmarks as well as real graph datasets. Our evaluation shows that both techniques are effective: RelaxMap achieves 70% parallel efficiency on eight cores, and prioritization improves algorithm performance by an additional 20-50% on average, depending on the graph properties. Additionally, RelaxMap converges in the similar number of iterations and provides solutions of equivalent quality as the serial Infomap implementation.

• 297. Bae, Seung-Hee
Umeå University, Faculty of Science and Technology, Department of Physics.
Scalable Flow-Based Community Detection for Large-Scale Network Analysis2013In: 2013 IEEE 13TH INTERNATIONAL CONFERENCE ON DATA MINING WORKSHOPS (ICDMW) / [ed] Ding, W Washio, T Xiong, H Karypis, G Thuraisingham, B Cook, D Wu, X, IEEE, 2013, p. 303-310Conference paper (Refereed)

Community-detection is a powerful approach to uncover important structures in large networks. Since networks often describe flow of some entity, flow-based community-detection methods are particularly interesting. One such algorithm is called Infomap, which optimizes the objective function known as the map equation. While Infomap is known to be an effective algorithm, its serial implementation cannot take advantage of multicore processing in modern computers. In this paper, we propose a novel parallel generalization of Infomap called RelaxMap. This algorithm relaxes concurrency assumptions to avoid lock overhead, achieving 70% parallel efficiency in shared-memory multicore experiments while exhibiting similar convergence properties and finding similar community structures as the serial algorithm. We evaluate our approach on a variety of real graph datasets as well as synthetic graphs produced by a popular graph generator used for benchmarking community detection algorithms. We describe the algorithm, the experiments, and some emerging research directions in high-performance community detection on massive graphs.

• 298.
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
Equilibrium solution to the lowest unique positive integer game2010In: Fluctuation and Noise Letters, ISSN 0219-4775, E-ISSN 1793-6780, Vol. 9, no 1, p. 61-68Article in journal (Refereed)

We address the equilibrium concept of a reverse auction game so that no one can enhance the individual payoff by a unilateral change when all the others follow a certain strategy. In this approach the combinatorial possibilities to consider become very much involved even for a small number of players, which has hindered a precise analysis in previous works. We here present a systematic way to reach the solution for a general number of players, and show that this game is an example of conflict between the group and the individual interests.

• 299.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Zipf's law unzipped2011In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, p. 043004-Article in journal (Refereed)

Why does Zipf's law give a good description of data from seemingly completely unrelated phenomena? Here it is argued that the reason is that they can all be described as outcomes of a ubiquitous random group division: the elements can be citizens of a country and the groups family names, or the elements can be all the words making up a novel and the groups the unique words, or the elements could be inhabitants and the groups the cities in a country, and so on. A Random Group Formation (RGF) is presented from which a Bayesian estimate is obtained based on minimal information: it provides the best prediction for the number of groups with $k$ elements, given the total number of elements, groups, and the number of elements in the largest group. For each specification of these three values, the RGF predicts a unique group distribution $N(k)\propto \exp(-bk)/k^{\gamma}$, where the power-law index $\gamma$ is a unique function of the same three values. The universality of the result is made possible by the fact that no system specific assumptions are made about the mechanism responsible for the group division. The direct relation between $\gamma$ and the total number of elements, groups, and the number of elements in the largest group, is calculated. The predictive power of the RGF model is demonstrated by direct comparison with data from a variety of systems. It is shown that $\gamma$ usually takes values in the interval $1\leq\gamma\leq 2$ and that the value for a given phenomena depends in a systematic way on the total size of the data set. The results are put in the context of earlier discussions on Zipf's and Gibrat's laws, $N(k)\propto k^{-2}$ and the connection between growth models and RGF is elucidated.

• 300.
Umeå University, Faculty of Science and Technology, Department of Physics.
Dept. of Physics, Sungkyunkwan Univ., Suwon, Korea.
Numerical Study of Game Theory2010In: New Physics, ISSN 0374-4914, Vol. 60, no 9, p. 943-951Article in journal (Other academic)

Game-theoretic approach has been providing a powerful tool in qualitative understanding of macroscopic social phenomena in social sciences, e.g., in economics and political science. Recently, researchers in physics, especially in statistical physics, use these game-theoretic approaches but in more quantitative way and have been producing a variety of interesting results in the new research area called ’sociophysics’ by studying human society as a complex system. This work introduces recent works that have tackled combinatorial complexities arising in game-theoretic studies with the aid of simplified assumptions and numerical computations. We first show how cooperation emerges in the prisoner’s dilemma game when each player’s memory capacity is enhanced and suggest that the intelligent tit-for-tat strategy plays a crucial role in the history of cooperation. And then it is numerically shown that there is a certain case of simultaneous coordination among many players where the system has a high risk of failure when everyone is willing to follow the coordination, which is actually higher than when some are not concerned about it. Lastly, we discuss mathematical treatment of an equilibrium solution for a reverse auction game, which is a variant of the minority game, and its computational approach.

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