| 1. |
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| 2. |
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| 3. |
- Jonsson, Robert, 1987
(författare)
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Quantum signaling in relativistic motion and across acceleration horizons
- 2017
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8121 .- 1751-8113. ; 50:35, s. Article no 355401 -
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Tidskriftsartikel (refereegranskat)abstract
- The quantum channel between two particle detectors provides a prototype framework for the study of wireless quantum communication via relativistic quantum fields. In this article we calculate the classical channel capacity between two Unruh-DeWitt detectors arising from couplings within the perturbative regime. To this end, we identify the detector states which achieve maximal signal strength. We use these results to investigate the impact of relativistic effects on signaling between detectors in inertial and uniformly accelerated motion which communicate via a massless field in Minkowski spacetime.
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| 4. |
- Paquette, Natalie M., et al.
(författare)
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BPS algebras, genus zero and the heterotic Monster
- 2017
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 50
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 IOP Publishing Ltd. In this note, we expand on some technical issues raised in (Paquette et al 2016 Commun. Number Theory Phys. 10 433-526) by the authors, as well as providing a friendly introduction to and summary of our previous work. We construct a set of heterotic string compactifications to 0 + 1 dimensions intimately related to the Monstrous moonshine module of Frenkel, Lepowsky, and Meurman (and orbifolds thereof). Using this model, we review our physical interpretation of the genus zero property of Monstrous moonshine. Furthermore, we show that the space of (second-quantized) BPS-states forms a module over the Monstrous Lie algebras - some of the first and most prominent examples of Generalized Kac-Moody algebras - constructed by Borcherds and Carnahan. In particular, we clarify the structure of the module present in the second-quantized string theory. We also sketch a proof of our methods in the language of vertex operator algebras, for the interested mathematician.
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| 5. |
- Argun, Aykut, et al.
(författare)
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Classification, inference and segmentation of anomalous diffusion with recurrent neural networks
- 2021
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 54:29
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Tidskriftsartikel (refereegranskat)abstract
- Countless systems in biology, physics, and finance undergo diffusive dynamics. Many of these systems, including biomolecules inside cells, active matter systems and foraging animals, exhibit anomalous dynamics where the growth of the mean squared displacement with time follows a power law with an exponent that deviates from 1. When studying time series recording the evolution of these systems, it is crucial to precisely measure the anomalous exponent and confidently identify the mechanisms responsible for anomalous diffusion. These tasks can be overwhelmingly difficult when only few short trajectories are available, a situation that is common in the study of non-equilibrium and living systems. Here, we present a data-driven method to analyze single anomalous diffusion trajectories employing recurrent neural networks, which we name RANDI. We show that our method can successfully infer the anomalous exponent, identify the type of anomalous diffusion process, and segment the trajectories of systems switching between different behaviors. We benchmark our performance against the state-of-the art techniques for the study of single short trajectories that participated in the Anomalous Diffusion (AnDi) challenge. Our method proved to be the most versatile method, being the only one to consistently rank in the top 3 for all tasks proposed in the AnDi challenge.
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| 6. |
- Pestun, Vasily, et al.
(författare)
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Localization techniques in quantum field theories
- 2017
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Ingår i: Journal of Physics A. - : IOP PUBLISHING LTD. - 1751-8113 .- 1751-8121. ; 50:44
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This is the foreword to the special issue on localization techniques in quantum field theory. The summary of individual chapters is given and their interrelation is discussed.
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| 7. |
- Cirillo, Emilio N.M., et al.
(författare)
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Deterministic reversible model of non-equilibrium phase transitions and stochastic counterpart
- 2020
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Ingår i: Journal of Physics A. - : Institute of Physics (IOP). - 1751-8113 .- 1751-8121. ; 53:30
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Tidskriftsartikel (refereegranskat)abstract
- Npoint particles move within a billiard table made of two circular cavities connected by a straight channel. The usual billiard dynamics is modified so that it remains deterministic, phase space volumes preserving and time reversal invariant. Particles move in straight lines and are elastically reflected at the boundary of the table, as usual, but those in a channel that are moving away from a cavity invert their motion (rebound), if their number exceeds a given thresholdT. When the geometrical parameters of the billiard table are fixed, this mechanism gives rise to non-equilibrium phase transitions in the largeNlimit: lettingT/Ndecrease, the homogeneous particle distribution abruptly turns into a stationary inhomogeneous one. The equivalence with a modified Ehrenfest two urn model, motivated by the ergodicity of the billiard with no rebound, allows us to obtain analytical results that accurately describe the numerical billiard simulation results. Thus, a stochastic exactly solvable model that exhibits non-equilibrium phase transitions is also introduced.
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| 8. |
- Drukker, Nadav, et al.
(författare)
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Roadmap on Wilson loops in 3d Chern-Simons-matter theories
- 2020
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Ingår i: Journal of Physics A. - : Institute of Physics Publishing (IOPP). - 1751-8113 .- 1751-8121. ; 53:17
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Forskningsöversikt (refereegranskat)abstract
- This is a compact review of recent results on supersymmetric Wilson loops in ABJ(M) and related theories. It aims to be a quick introduction to the state of the art in the field and a discussion of open problems. It is divided into short chapters devoted to different questions and techniques. Some new results, perspectives and speculations are also presented. We hope this might serve as a baseline for further studies of this topic.
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| 9. |
- Fuchs, Jürgen, 1957-, et al.
(författare)
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From non-semisimple Hopf algebras to correlation functions for logarithmic CFT
- 2013
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Ingår i: Journal of Physics A. - : IOP Publishing. - 0305-4470 .- 1361-6447. ; 46:49
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Tidskriftsartikel (refereegranskat)abstract
- We use factorizable finite tensor categories, and specifically the representation categories of factorizable ribbon Hopf algebras H, as a laboratory for exploring bulk correlation functions in local logarithmic conformal field theories. For any ribbon Hopf algebra automorphism ω of H, we present a candidate for the space of bulk fields and endow it with a natural structure of a commutative symmetric Frobenius algebra. We derive an expression for the corresponding bulk partition functions as bilinear combinations of irreducible characters; as a crucial ingredient this involves the Cartan matrix of the category. We also show how for any candidate bulk state space of the type we consider, correlation functions of bulk fields for closed oriented world sheets of any genus can be constructed that are invariant under the natural action of the relevant mapping class group
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| 10. |
- Månsson, Teresia, 1974-
(författare)
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Is there a tower of charges to be discovered?
- 2007
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Ingår i: Journal of Physics A. - : Institute of Physics Publishing (IOPP). - 1751-8113 .- 1751-8121. ; 41, s. 194014-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate higher-loop integrability for a q-deformation of the -sector of SYM theory. First we construct a generalization of the long-range spin chain, which for the lowest orders describes the non-deformed dilatation operator. This generalized model is built up from Temperley–Lieb algebra generators and describes the deformed theory to at least two loops. When constructing the model we have demanded the existence of one commuting charge, which puts strong constraints on the parameters to three-loop orders. We also write the five first charges for this model at two-loops order. Our main goal is to obtain an explicit expression for an infinite number of commuting charges, all commuting with the dilatation operator. This would imply integrability. As a step towards this goal we present in this paper an expression for a generic local charge of the one-loop dilatation operator, which happens to be a generator of the Temperley–Lieb algebra.
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| 11. |
- Ammar, F., et al.
(författare)
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Ternary q-Virasoro-Witt Hom-Nambu-Lie algebras
- 2010
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 43:26, s. 265204-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we construct ternary q-Virasoro-Witt algebras which q-deform the ternary Virasoro-Witt algebras constructed by Curtright, Fairlie and Zachos using su(1, 1) enveloping algebra techniques. The ternary Virasoro-Witt algebras constructed by Curtright, Fairlie and Zachos depend on a parameter and are not Nambu-Lie algebras for all but finitely many values of this parameter. For the parameter values for which the ternary Virasoro-Witt algebras are Nambu-Lie, the corresponding ternary q-Virasoro-Witt algebras constructed in this paper are also Hom-Nambu-Lie because they are obtained from the ternary Nambu-Lie algebras using the composition method. For other parameter values this composition method does not yield a Hom-Nambu-Lie algebra structure for q-Virasoro-Witt algebras. We show however, using a different construction, that the ternary Virasoro-Witt algebras of Curtright, Fairlie and Zachos, as well as the general ternary q-Virasoro-Witt algebras we construct, carry a structure of the ternary Hom-Nambu-Lie algebra for all values of the involved parameters.
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| 12. |
- Anderson, Johan, 1973, et al.
(författare)
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The probability density function tail of the Kardar–Parisi–Zhang equation in the strongly nonlinear regime
- 2016
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8121 .- 1751-8113. ; 49:50, s. 505001-
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Tidskriftsartikel (refereegranskat)abstract
- An analytical derivation of the probability density function (PDF) tail describing the strongly correlated interface growth governed by the nonlinear Kardar–Parisi–Zhang equation is provided. The PDF tail exactly coincides with a Tracy–Widom distribution i.e. a PDF tail proportional to exp(-cw_2^(3/2)), where w_2 is the the width of the interface. The PDF tail is computed by the instanton method in the strongly non-linear regime within the Martin–Siggia– Rose framework using a careful treatment of the non-linear interactions. Inaddition, the effect of spatial dimensions on the PDF tail scaling is discussed. This gives a novel approach to understand the rightmost PDF tail of the interface width distribution and the analysis suggests that there is no uppercritical dimension.
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| 13. |
- Behrndt, Jussi, et al.
(författare)
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On the number of negative eigenvalues of the Laplacian on a metric graph
- 2010
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 43:47
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Tidskriftsartikel (refereegranskat)abstract
- The number of negative eigenvalues of self-adjoint Laplacians on metric graphs is calculated in terms of the boundary conditions and the underlying geometric structure. This extends and complements earlier results by Kostrykin and Schrader (2006 Contemp. Math. 415 201-25).
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| 14. |
- Bernland, Anders, et al.
(författare)
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Sum rules and constraints on passive systems
- 2011
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 44:14
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Tidskriftsartikel (refereegranskat)abstract
- A passive system is one that cannot produce energy, a property that naturally poses constraints on the system. A system in convolution form is fully described by its transfer function, and the class of Herglotz functions, holomorphic functions mapping the open upper half plane to the closed upper half plane, is closely related to the transfer functions of passive systems. Following a well-known representation theorem, Herglotz functions can be represented by means of positive measures on the real line. This fact is exploited in this paper in order to rigorously prove a set of integral identities for Herglotz functions that relate weighted integrals of the function to its asymptotic expansions at the origin and infinity. The integral identities are the core of a general approach introduced here to derive sum rules and physical limitations on various passive physical systems. Although similar approaches have previously been applied to a wide range of specific applications, this paper is the first to deliver a general procedure together with the necessary proofs. This procedure is described thoroughly, and exemplified with examples from electromagnetic theory.
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| 15. |
- Forini, V., et al.
(författare)
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One-loop spectroscopy of semiclassically quantized strings: bosonic sector
- 2015
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8121 .- 1751-8113. ; 48:8, s. Art. no. 085401-
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Tidskriftsartikel (refereegranskat)abstract
- We make a further step in the analytically exact quantization of spinning string states in semiclassical approximation, by evaluating the exact one-loop partition function for a class of two-spin string solutions for which quadratic fluctuations form a non-trivial system of coupled modes. This is the case of a folded string in the SU(2) sector, in the limit described by a quantum Landau-Lifshitz model. The same applies to the full bosonic sector of fluctuations over the folded spinning string in AdS(5) with an angular momentum J in S-5. Fluctuations are governed by a special class of fourth-order differential operators, with coefficients being meromorphic functions on the torus, which we are able to solve exactly.
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| 16. |
- Forini, V., et al.
(författare)
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The generalized cusp in AdS(4) x CP3 and more one-loop results from semiclassical strings
- 2013
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8121 .- 1751-8113. ; 46:11
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Tidskriftsartikel (refereegranskat)abstract
- We evaluate the exact one-loop partition function for fundamental strings whose world surface ends on a cusp at the boundary of AdS(4) and has a 'jump' in CP3. This allows us to extract the stringy prediction for the ABJM-generalized cusp anomalous dimension Gamma(ABJM)(cusp) (phi, theta) up to NLO in sigma-model perturbation theory. With a similar analysis, we present the exact partition functions for folded closed string solutions moving in the AdS(3) parts of AdS(4) x CP3 and AdS(3) x S-3 x S-3 x S-1 backgrounds. Results are obtained applying to the string solutions relevant for the AdS(4)/CFT3 and AdS(3)/CFT2 correspondence the tools previously developed for their AdS(5) x S-5 counterparts.
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| 17. |
- Iguri, Sergio, et al.
(författare)
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Some recursive formulas for Selberg-type integrals
- 2010
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Ingår i: JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 43:6
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Tidskriftsartikel (refereegranskat)abstract
- A set of recursive relations satisfied by Selberg-type integrals involving monomial symmetric polynomials are derived, generalizing previous results in Aomoto (1987) SIAM J. Math. Anal. 18 545-49 and Iguri (2009) Lett. Math. Phys. 89 141-58. These formulas provide a well-defined algorithm for computing Selberg-Schur integrals whenever the Kostka numbers relating Schur functions and the corresponding monomial polynomials are explicitly known. We illustrate the usefulness of our results discussing some interesting examples.
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| 18. |
- Karlström, Olov, et al.
(författare)
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A diagrammatic description of the equations of motion, current and noise within the second-order von Neumann approach
- 2013
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 46:6
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the second-order von Neumann approach from a diagrammatic point of view and demonstrate its equivalence with the resonant tunneling approximation. The investigation of higher order diagrams shows that the method correctly reproduces the equation of motion for the single-particle reduced density matrix of an arbitrary non-interacting many-body system. This explains why the method reproduces the current exactly for such systems. We go on to show, however, that diagrams not included in the method are needed to calculate exactly higher cumulants of the charge transport. This thorough comparison sheds light on the validity of all these self-consistent second-order approaches. We analyze the discrepancy between the noise calculated by our method and the exact Levitov formula for a simple non-interacting quantum dot model. Furthermore, we study the noise of the canyon of current suppression in a two-level dot, a phenomenon that requires the inclusion of electron-electron interaction as well as higher order tunneling processes.
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| 19. |
- Kieburg, Mario, et al.
(författare)
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Arbitrary rotation invariant random matrix ensembles and supersymmetry: orthogonal and unitary-symplectic case
- 2009
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 42:27
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Tidskriftsartikel (refereegranskat)abstract
- Recently, the supersymmetry method was extended from Gaussian ensembles to arbitrary unitarily invariant matrix ensembles by generalizing the Hubbard-Stratonovich transformation. Here, we complete this extension by including arbitrary orthogonally and unitary-symplectically invariant matrix ensembles. The results are equivalent to, but the approach is different from, the superbosonization formula. We express our results in a unifying way. We also give explicit expressions for all one-point functions and discuss features of the higher order correlations.
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| 20. |
- Kohler, Heiner, et al.
(författare)
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Survival probability of a doorway state in regular and chaotic environments
- 2010
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 43:21
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Tidskriftsartikel (refereegranskat)abstract
- We calculate the survival probability of a special state which couples randomly to a regular or chaotic environment. The environment is modeled by a suitably chosen random matrix ensemble. The exact results exhibit non-perturbative features as revival of probability and non-ergodicity. The role of background complexity and coupling complexity is discussed as well.
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| 21. |
- Lizana, Ludvig, et al.
(författare)
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Tracer particles in two-dimensional elastic networks diffuse logarithmically slow
- 2017
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 50:3
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Tidskriftsartikel (refereegranskat)abstract
- Several experiments on tagged molecules or particles in living systems suggest that they move anomalously slow - their mean squared displacement (MSD) increase slower than linearly with time. Leading models aimed at understanding these experiments predict that the MSD grows as a power law with a growth exponent that is smaller than unity. However, in some experiments the growth is so slow (fitted exponent ∼0.1-0.2) that they hint towards other mechanisms at play. In this paper, we theoretically demonstrate how in-plane collective modes excited by thermal fluctuations in a two dimensional membrane lead to logarithmic time dependence for the the tracer particle's MSD.
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| 22. |
- Lundholm, Douglas
(författare)
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Geometric extensions of many-particle Hardy inequalities
- 2015
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Ingår i: Journal of Physics A. - : Institute of Physics Publishing (IOPP). - 1751-8113 .- 1751-8121. ; 48:17
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Tidskriftsartikel (refereegranskat)abstract
- Certain many-particle Hardy inequalities are derived in a simple and systematic way using the so-called ground state representation for the Laplacian on a subdomain of R^n. This includes geometric extensions of the standard Hardy inequalities to involve volumes of simplices spanned by a subset of points. Clifford/multilinear algebra is employed to simplify geometric computations. These results and the techniques involved are relevant for classes of exactly solvable quantum systems such as the Calogero-Sutherland models and their higher-dimensional generalizations, as well as for membrane matrix models, and models of more complicated particle interactions of geometric character.
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| 23. |
- Manninen, M., et al.
(författare)
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Electron correlation in metal clusters, quantum dots and quantum rings
- 2009
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 42:21, s. 214019-214019
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Konferensbidrag (refereegranskat)abstract
- This paper presents a few case studies of finite electron systems for which strong correlations play a dominant role. In simple metal clusters, the valence electrons determine the stability and shape of the clusters. The ionic skeleton of alkali metals is soft, and cluster geometries are often solely determined by electron correlations. In quantum dots and rings, the electrons may be confined by an external electrostatic potential formed by a gated heterostructure. In the low-density limit, the electrons may form the so-called Wigner molecules, for which the many-body quantum spectra reveal the classical vibration modes. High rotational states increase the tendency for the electrons to localize. At low angular momenta, the electrons may form a quantum Hall liquid with vortices. In this case, the vortices act as quasi-particles with long-range effective interactions that localize in a vortex molecule, in much analogy with the electron localization at strong rotation.
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| 24. |
- Marlettta, Marco, et al.
(författare)
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A Laplace operator with boundary conditions singular at one point
- 2009
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Ingår i: JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 42:12
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Tidskriftsartikel (refereegranskat)abstract
- We discuss a recent paper of Berry and Dennis (J. Phys. A: Math. Theor. 2008 41 135203) concerning a Laplace operator on a smooth domain with singular boundary condition. We explain a paradox in the article (J. Phys. A: Math. Theor. 2008 41 135203) and show that if a certain additional condition is imposed, the result is a spectral problem for a self-adjoint operator having only eigenvalues and no continuous spectrum. The eigenvalues accumulate at ±∞ only, and we obtain the asymptotic behaviours of the counting functions n+(λ) and n−(λ) for positive and negative eigenvalues. The physical meaning of the additional boundary condition is not yet clear.
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| 25. |
- Marsland, Stephen, et al.
(författare)
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On conformal variational problems and free boundary continua
- 2014
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8121 .- 1751-8113. ; 47:14, s. Art. no. 145204-
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Tidskriftsartikel (refereegranskat)abstract
- We develop a framework for deriving governing partial differential equations for variational problems on spaces of conformal mappings. The main motivation is to obtain differential equations for the conformal motion of free boundary continua, of interest in image and shape registration. A fundamental tool in the paper, the Hodge–Morrey–Friedrichs decompositions of differential forms on manifolds with boundaries, is used to identify the orthogonal complement of the subspace of conformal mappings. A detailed presentation of these decompositions is included in the paper.
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| 26. |
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| 27. |
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| 28. |
- Sohl, Christian, et al.
(författare)
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Physical limitations on broadband scattering by heterogeneous obstacles
- 2007
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 40:36, s. 11165-11182
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, new physical limitations on the extinction cross section and broadband scattering are investigated. A measure of broadband scattering in terms of the integrated extinction is derived for a large class of scatterers based on the holomorphic properties of the forward scattering dyadic. Closed-form expressions of the integrated extinction are given for the homogeneous ellipsoids, and theoretical bounds are discussed for arbitrary heterogeneous scatterers. Finally, the theoretical results are illustrated by numerical computations for a series of generic scatterers
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| 29. |
- Splettstoesser, Janine, et al.
(författare)
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Two-particle Aharonov-Bohm effect in electronic interferometers
- 2010
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Ingår i: Journal Of Physics A-Mathematical And Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 43:35
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Konferensbidrag (refereegranskat)abstract
- We review recent theoretical investigations on the two-particle Aharonov-Bohm effect and its relation to entanglement production and detection. The difficulties of the entanglement detection due to dephasing and finite temperature are discussed regarding a recent experimental realization of a two-particle Aharonov-Bohm interferometer [15]. We also discuss a theoretical proposal for a two-particle Aharonov-Bohm interferometer, which as against the finite bias setup is driven with dynamical single-electron sources allowing for the tunable production of time-bin entanglement.
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| 30. |
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| 31. |
- Tejedor, Vincent, et al.
(författare)
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Encounter distribution of two random walkers on a finite one-dimensional interval
- 2011
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 44:39
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Tidskriftsartikel (refereegranskat)abstract
- We analyse the first-passage properties of two random walkers confined to a finite one-dimensional domain. For the case of absorbing boundaries at the endpoints of the interval, we derive the probability that the two particles meet before either one of them becomes absorbed at one of the boundaries. For the case of reflecting boundaries, we obtain the mean first encounter time of the two particles. Our approach leads to closed-form expressions that are more easily tractable than a previously derived solution in terms of the Weierstrass' elliptic function.
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| 32. |
- Åberg, Sven
(författare)
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Spectral density of autocorrelated Wishart-Levy matrices
- 2013
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 46:34
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Tidskriftsartikel (refereegranskat)abstract
- Spectral properties of time-correlated Wishart-Levy matrices are studied. The correlation matrices are built from ensembles of time series obtained from a deterministic chaotic one-dimensional map with Cauchy distributed entries. Dependence of the spectral density on autocorrelations of the time series is investigated. Two basically different regimes of the spectra appear: extended states with small eigenvalues and localized states with high eigenvalues. Autocorrelations in the time series imply a decrease of the fraction of localized states as 1/(1+tau(0)), where tau(0) is the correlation time. For sufficiently large time correlations only extended states remain with eigenvalues clustered around zero.
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| 33. |
- Ögren, Magnus, 1977-, et al.
(författare)
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On the dynamics of the Fermi-Bose model
- 2013
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Ingår i: Journal of Physics A. - : Institute of Physics (IOP). - 1751-8113 .- 1751-8121. ; 46:1
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Tidskriftsartikel (refereegranskat)abstract
- We consider the exponential matrix representing the dynamics of the Fermi-Bose model in an undepleted bosonic field approximation. A recent application of this model is molecular dimers dissociating into its atomic compounds. The problem is solved in D spatial dimensions by dividing the system matrix into blocks with generalizations of Hankel matrices, here referred to as D-block-Hankel matrices. The method is practically useful for treating large systems, i.e. dense computational grids or higher spatial dimensions, either on a single standard computer or a cluster. In particular the results can be used for studies of three-dimensional physical systems of arbitrary geometry. We illustrate the generality of our approach by giving numerical results for the dynamics of Glauber type atomic pair correlation functions for a non-isotropic three-dimensional harmonically trapped molecular Bose-Einstein condensate.
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| 34. |
- Aas, E., et al.
(författare)
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The exact phase diagram for a semipermeable TASEP with nonlocal boundary jumps
- 2019
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Ingår i: Journal of Physics A. - : Institute of Physics Publishing (IOPP). - 1751-8113 .- 1751-8121. ; 52:35
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Tidskriftsartikel (refereegranskat)abstract
- We consider a finite one-dimensional totally asymmetric simple exclusion process with four types of particles, {1, 0, 1, }, in contact with reservoirs. Particles of species 0 can neither enter nor exit the lattice, and those of species are constrained to lie at the first and last site. Particles of species 1 enter from the left reservoir into either the first or second site, move rightwards, and leave from either the last or penultimate site. Conversely, particles of species 1 enter from the right reservoir into either the last or penultimate site, move leftwards, and leave from either the first or last site. This dynamics is motivated by a natural random walk on the Weyl group of type D. We compute the exact nonequilibrium steady state distribution using a matrix ansatz building on earlier work of Arita. We then give explicit formulas for the nonequilibrium partition function as well as densities and currents of all species in the steady state, and derive the phase diagram.
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| 35. |
- Akemann, Gernot, et al.
(författare)
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Universal eigenvector correlations in quaternionic Ginibre ensembles
- 2020
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Ingår i: Journal of Physics A. - : IOP PUBLISHING LTD. - 1751-8113 .- 1751-8121. ; 53:14
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Tidskriftsartikel (refereegranskat)abstract
- Non-Hermitian random matrices enjoy non-trivial correlations in the statistics of their eigenvectors. We study the overlap among left and right eigenvectors in Ginibre ensembles with quaternion valued Gaussian matrix elements. This concept was introduced by Chalker and Mehlig in the complex Ginibre ensemble. Using a Schur decomposition, for harmonic potentials we can express the overlap in terms of complex eigenvalues only, coming in conjugate pairs in this symmetry class. Its expectation value leads to a Pfaffian determinant, for which we explicitly compute the matrix elements for the induced Ginibre ensemble with zero eigenvalues, for finite matrix size N. In the macroscopic large-N limit in the bulk of the spectrum we recover the limiting expressions of the complex Ginibre ensemble for the diagonal and off-diagonal overlap, which are thus universal.
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| 36. |
- Alday, Fernando, et al.
(författare)
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The Pollica perspective on the (super)-conformal world
- 2021
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Ingår i: Journal of Physics A. - : Institute of Physics Publishing (IOPP). - 1751-8113 .- 1751-8121. ; 54:30
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Forskningsöversikt (refereegranskat)abstract
- This manuscript samples a series of recent results in the quest for a systematic understanding of the space of conformal field theories, with a particular focus on theories with extended supersymmetry. The large majority of results reported here were presented during the second Pollica summer workshop which took place from June 3-21 2019 and focused on mathematical and geometric tools for superconformal field theories. This manuscript represents in many ways a partial summary of the workshop.
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| 37. |
- Andersson, Ole, et al.
(författare)
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Aligned SICs and embedded tight frames in even dimensions
- 2019
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Ingår i: Journal of Physics A. - : Institute of Physics (IOP). - 1751-8113 .- 1751-8121. ; 52:42
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Tidskriftsartikel (refereegranskat)abstract
- Alignment is a geometric relation between pairs of Weyl-Heisenberg SICs, one in dimension d and another in dimension d(d - 2), manifesting a well-founded conjecture about a number-theoretical connection between the SICs. In this paper, we prove that if d is even, the SIC in dimension d(d - 2) of an aligned pair can be partitioned into (d - 2)(2) tight d(2)-frames of rank d(d - 1)/2 and, alternatively, into d(2) tight (d - 2)(2) -frames of rank (d - 1) (d - 2)/2. The corresponding result for odd d is already known, but the proof for odd d relies on results which are not available for even d. We develop methods that allow us to overcome this issue. In addition, we provide a relatively detailed study of parity operators in the Clifford group, emphasizing differences in the theory of parity operators in even and odd dimensions and discussing consequences due to such differences. In a final section, we study implications of alignment for the symmetry of the SIC.
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| 38. |
- Andrei, N., et al.
(författare)
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Boundary and defect CFT : open problems and applications
- 2020
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Ingår i: Journal of Physics A: Mathematical and Theoretical. - : IOP PUBLISHING LTD. - 1751-8113 .- 1751-8121. ; 53:45
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Forskningsöversikt (refereegranskat)abstract
- A review of Boundary and defect conformal field theory: open problems and applications, following a workshop held at Chicheley Hall, Buckinghamshire, UK, 7-8 Sept. 2017. We attempt to provide a broad, bird's-eye view of the latest progress in boundary and defect conformal field theory in various sub-fields of theoretical physics, including the renormalization group, integrability, conformal bootstrap, topological field theory, supersymmetry, holographic duality, and more. We also discuss open questions and promising research directions in each of these sub-fields, and combinations thereof.
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| 39. |
- Arutyunov, Gleb, et al.
(författare)
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Superintegrability of geodesic motion on the sausage model
- 2017
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 50:24
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 40. |
- Aurell, Erik, et al.
(författare)
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A closure for the master equation starting from the dynamic cavity method
- 2023
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 56:17
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Tidskriftsartikel (refereegranskat)abstract
- We consider classical spin systems evolving in continuous time with interactions given by a locally tree-like graph. Several approximate analysis methods have earlier been reported based on the idea of Belief Propagation / cavity method. We introduce a new such method which can be derived in a more systematic manner using the theory of Random Point Processes. Within this approach, the master equation governing the system's dynamics is closed via a set of differential equations for the auxiliary cavity probabilities. The numerical results improve on the earlier versions of the closure on several important classes of problems. We re-visit here the cases of the Ising ferromagnet and the Viana-Bray spin-glass model.
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| 41. |
- Aurell, Erik, et al.
(författare)
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An operator derivation of the Feynman-Vernon theory, with applications to the generating function of bath energy changes and to an-harmonic baths
- 2020
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Ingår i: Journal of Physics A. - : Institute of Physics Publishing (IOPP). - 1751-8113 .- 1751-8121. ; 53:27
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Tidskriftsartikel (refereegranskat)abstract
- We present a derivation of the Feynman-Vernon approach to open quantum systems in the language of super-operators. We show that this gives a new and more direct derivation of the generating function of energy changes in a bath, or baths. As found previously, this generating function is given by a Feynman-Vernon-like influence functional, with only time shifts in the kernels coupling the forward and backward paths. We further show that the new approach extends to an-harmonic and possible non-equilibrium baths, provided that the interactions are bi-linear, and that the baths do not interact between themselves. Such baths are characterized by non-trivial cumulants. Every non-zero cumulant of certain environment correlation functions is thus a kernel in a higher-order term in the Feynman-Vernon action.
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| 42. |
- Azimi Mousolou, Vahid, et al.
(författare)
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Entangling power of holonomic gates in atom-based systems
- 2018
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 51:47
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Tidskriftsartikel (refereegranskat)abstract
- Entanglement is one of the main resources of quantum computation, and entangling power of a quantum system is a crucial element in the universality and efficiency of a proposed architecture for realization of quantum processing. Our goal here is to study the entangling power of holonomic gates in some particular systems. We explore the holonomy-induced entanglement, by means of nonadiabatic quantum holonomies, through different types of interactions in atom-based systems, namely, the tripod-type interaction induced by the quantum Zeno effect between three-level atoms, as well as the Λ-type interaction arising from dipole–dipole or van der Waals forces between high-lying states of two-level atoms in systems consisting of N optically trapped identical atoms. Our analysis shows that although the two schemes provide completely separate classes of entangling gates, both schemes permit for full entangling power and also in the sense of quantum efficiency both families of entanglers consist of holonomic gates that have the same efficiency in quantum algorithms. Besides, we observe that holonomy-induced entanglement characteristics remarkably depend on the interaction configuration of the system.
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| 43. |
- Basieva, Irina, 1974-, et al.
(författare)
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Conditional probability framework for entanglement and its decoupling from tensor product structure
- 2022
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Ingår i: Journal of Physics A. - : Institute of Physics Publishing (IOPP). - 1751-8113 .- 1751-8121. ; 55:39
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Tidskriftsartikel (refereegranskat)abstract
- Our aim is to make a step toward clarification of foundations for the notion of entanglement (both physical and mathematical) by representing it in the conditional probability framework. In Schrodinger's words, this is entanglement of knowledge which can be extracted via conditional measurements. In particular, quantum probabilities are interpreted as conditional ones (as, e.g., by Ballentine). We restrict considerations to perfect conditional correlations (PCC) induced by measurements ('EPR entanglement'). Such entanglement is coupled to the pairs of observables with the projection type state update as the back action of measurement. In this way, we determine a special class of entangled states. One of our aims is to decouple the notion of entanglement from the compound systems. The rigid association of entanglement with the state of a few body systems stimulated its linking with quantum nonlocality ('spooky action at a distance'). However, already by Schrodinger entanglement was presented as knotting of knowledge (about statistics) for one observable A with knowledge about another observable B.
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| 44. |
- Bengtsson, Ingemar, 1957-, et al.
(författare)
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Dimension towers of SICS: II. Some constructions
- 2022
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Ingår i: Journal of Physics a-Mathematical and Theoretical. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 55:21
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Tidskriftsartikel (refereegranskat)abstract
- A SIC is a maximal equiangular tight frame in a finite dimensional Hilbert space. Given a SIC in dimension d, there is good evidence that there always exists an aligned SIC in dimension d(d - 2), having predictable symmetries and smaller equiangular tight frames embedded in them. We provide a recipe for how to calculate sets of vectors in dimension d(d - 2) that share these properties. They consist of maximally entangled vectors in certain subspaces defined by the numbers entering the d dimensional SIC. However, the construction contains free parameters and we have not proven that they can always be chosen so that one of these sets of vectors is a SIC. We give some worked examples that, we hope, may suggest to the reader how our construction can be improved. For simplicity we restrict ourselves to the case of odd dimensions.
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| 45. |
- Berkolaiko, Gregory, et al.
(författare)
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Edge connectivity and the spectral gap of combinatorial and quantum graphs
- 2017
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 50:36
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Tidskriftsartikel (refereegranskat)abstract
- We derive a number of upper and lower bounds for the first nontrivial eigenvalue of Laplacians on combinatorial and quantum graph in terms of the edge connectivity, i.e. the minimal number of edges which need to be removed to make the graph disconnected. On combinatorial graphs, one of the bounds corresponds to a well-known inequality of Fiedler, of which we give a new variational proof. On quantum graphs, the corresponding bound generalizes a recent result of Band and Levy. All proofs are general enough to yield corresponding estimates for the p-Laplacian and allow us to identify the minimizers. Based on the Betti number of the graph, we also derive upper and lower bounds on all eigenvalues which are 'asymptotically correct', i.e. agree with the Weyl asymptotics for the eigenvalues of the quantum graph. In particular, the lower bounds improve the bounds of Friedlander on any given graph for all but finitely many eigenvalues, while the upper bounds improve recent results of Ariturk. Our estimates are also used to derive bounds on the eigenvalues of the normalized Laplacian matrix that improve known bounds of spectral graph theory.
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| 46. |
- Bern, Zvi, et al.
(författare)
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The SAGEX review on scattering amplitudes Chapter 2 : An invitation to color-kinematics duality and the double copy
- 2022
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 55:44
-
Forskningsöversikt (refereegranskat)abstract
- Advances in scattering amplitudes have exposed previously-hidden color-kinematics and double-copy structures in theories ranging from gauge and gravity theories to effective field theories such as chiral perturbation theory and the Born-Infeld model. These novel structures both simplify higher-order calculations and pose tantalizing questions related to a unified framework underlying relativistic quantum theories. This introductory mini-review article invites further exploration of these topics. After a brief introduction to color-kinematics duality and the double copy as they emerge at tree and loop-level in gauge and gravity theories, we present two distinct examples: (1) an introduction to the web of double-copy-constructible theories, and (2) a discussion of the application of the double copy to calculation relevant to gravitational-wave physics.
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| 47. |
- Berntson, Bjorn K., et al.
(författare)
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A new way to classify 2D higher order quantum superintegrable systems
- 2020
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 53:49
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Tidskriftsartikel (refereegranskat)abstract
- We revise a method by Kalnins, Kress and Miller (2010) for constructing a canonical form for symmetry operators of arbitrary order for the Schrodinger eigenvalue equation H psi equivalent to (Delta(2) + V)psi = E psi on any 2D Riemannian manifold, real or complex, that admits a separation of variables in some orthogonal coordinate system. We apply the method, as an example, to revisit the Tremblay and Winternitz (2010) derivation of the Painleve VI potential for a 3rd order superintegrable flat space system that separates in polar coordinates and, as new results, we give a listing of the possible potentials on the two-sphere that separate in spherical coordinates and all two-hyperbolic (two-sheet) potentials separating in horocyclic coordinates. In particular, we show that the Painleve VI potential also appears for a 3rd order superintegrable system on the two-sphere that separates in spherical coordinates, as well as a 3rd order superintegrable system on the two-hyperboloid that separates in spherical coordinates and one that separates in horocyclic coordinates. Our aim is to develop tools for analysis and classification of higher order superintegrable systems on any 2D Riemannian space, not just Euclidean space.
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| 48. |
- Berntson, Bjorn K., et al.
(författare)
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Multi-solitons of the half-wave maps equation and Calogero-Moser spin-pole dynamics
- 2020
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 53:50
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Tidskriftsartikel (refereegranskat)abstract
- We consider the half-wave maps (HWM) equation which provides a continuum description of the classical Haldane-Shastry spin chain on the real line. We present exact multi-soliton solutions of this equation. Our solutions describe solitary spin excitations that can move with different velocities and interact in a non-trivial way. We make an ansatz for the solution allowing for an arbitrary number of solitons, each described by a pole in the complex plane and a complex spin variable, and we show that the HWM equation is satisfied if these poles and spins evolve according to the dynamics of an exactly solvable spin Calogero-Moser (CM) system with certain constraints on initial conditions. We also find first order equations providing a Backlund transformation of this spin CM system, generalize our results to the periodic HWM equation, and provide plots that visualize our soliton solutions.
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| 49. |
- Bissi, Agnese, et al.
(författare)
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All loop structures in supergravity amplitudes on AdS(5) x S-5 from CFT
- 2021
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Ingår i: Journal of Physics A. - : Institute of Physics Publishing (IOPP). - 1751-8113 .- 1751-8121. ; 54:32
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Tidskriftsartikel (refereegranskat)abstract
- We compute a set of structures which appear in the four-point function of protected operators of dimension two in N = 4 super Yang Mills with SU(N) gauge group, at any order in a large N expansion. They are determined only by leading order CFT data. By focusing on a specific limit, we make connection with the dual supergravity amplitude in flat space, where such structures correspond to iterated s-cuts. We make several checks and we conjecture that the same interpretation holds for supergravity amplitudes on AdS(5) x S-5.
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| 50. |
- Borsato, Riccardo, et al.
(författare)
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Marginal deformations of WZW models and the classical Yang-Baxter equation
- 2019
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Ingår i: Journal of Physics A. - : IOP Publishing. - 1751-8113 .- 1751-8121. ; 52:22
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Tidskriftsartikel (refereegranskat)abstract
- We show how so-called Yang-Baxter (YB) deformations of sigma models, based on an R-matrix solving the classical Yang-Baxter equation (CYBE), give rise to marginal current-current deformations when applied to the Wess-Zumino-Witten (WZW) model. For non-compact groups these marginal deformations are more general than the ones usually considered, since they can involve a non-Abelian current subalgebra. We classify such deformations of the AdS(3) x S-3 string.
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