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García-García, Antonio M.; Jia, Yiyang; Verbaarschot, Jacobus J.M.
Funding organisation: SCOAP3, CERN, Geneva (Switzerland)
arXiv e-print [ PDF ]2018
Funding organisation: SCOAP3, CERN, Geneva (Switzerland)
arXiv e-print [ PDF ]2018
AbstractAbstract
[en] We analytically evaluate the moments of the spectral density of the -body Sachdev-Ye-Kitaev (SYK) model, and obtain order corrections for all moments, where is the total number of Majorana fermions. To order , moments are given by those of the weight function of the Q-Hermite polynomials. Representing Wick contractions by rooted chord diagrams, we show that the correction for each chord diagram is proportional to the number of triangular loops of the corresponding intersection graph, with an extra grading factor when is odd. Therefore the problem of finding corrections is mapped to a triangle counting problem. Since the total number of triangles is a purely graph-theoretic property, we can compute them for the and SYK models, where the exact moments can be obtained analytically using other methods, and therefore we have solved the moment problem for any to accuracy. The moments are then used to obtain the spectral density of the SYK model to order . We also obtain an exact analytical result for all contraction diagrams contributing to the moments, which can be evaluated up to eighth order. This shows that the Q-Hermite approximation is accurate even for small values of .
Primary Subject
Source
Available from http://dx.doi.org/10.1007/JHEP04(2018)146; Available from http://repo.scoap3.org/record/25405; PUBLISHER-ID: JHEP04(2018)146; ARXIV:1801.02696; OAI: oai:repo.scoap3.org:25405; Copyright (c) OPEN ACCESS, © The Authors; This article is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.; Country of input: International Atomic Energy Agency (IAEA)
Record Type
Journal Article
Journal
Journal of High Energy Physics (Online); ISSN 1029-8479;
; v. 2018(04); p. 146

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Capolupo, A.; Giampaolo, S.M.; Hiesmayr, B.C.; Vitiello, G., E-mail: capolupo@sa.infn.it
arXiv e-print [ PDF ]2018
arXiv e-print [ PDF ]2018
AbstractAbstract
[en] We analyze the non-cyclic geometric phase for neutrinos. We find that the geometric phase and the total phase associated to the mixing phenomenon provide a theoretical tool to distinguish between Dirac and Majorana neutrinos. Our results hold for neutrinos propagating in vacuum and through the matter. We feed the values of the experimental parameters in our formulas in order to make contact with experiments. Although it remains an open question how the geometric phase of neutrinos could be detected, our theoretical results may open new scenarios in the investigation of the neutrino nature.
Primary Subject
Source
S0370269318302053; Available from http://dx.doi.org/10.1016/j.physletb.2018.03.016; Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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Journal Article
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Hirsch, Martin; Srivastava, Rahul; Valle, José W.F., E-mail: mahirsch@ific.uv.es, E-mail: rahulsri@ific.uv.es, E-mail: valle@ific.uv.es
arXiv e-print [ PDF ]2018
arXiv e-print [ PDF ]2018
AbstractAbstract
[en] According to the “Black Box” theorem the experimental confirmation of neutrinoless double beta decay () would imply that at least one of the neutrinos is a Majorana particle. However, a null signal cannot decide the nature of neutrinos, as it can be suppressed even for Majorana neutrinos. In this letter we argue that if the null decay signal is accompanied by a quadruple beta decay signal, then at least one neutrino should be a Dirac particle. This argument holds irrespective of the underlying processes leading to such decays.
Primary Subject
Source
S0370269318302697; Available from http://dx.doi.org/10.1016/j.physletb.2018.03.073; Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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Journal Article
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AbstractAbstract
[en] A necessary condition for a particle to be its own Majorana particle is to have no charge. Quasi-particles are a concept that allows an easier description of the collective behaviour of electrons in a metal. The behaviour of independent quasi-particles is representative of the sum of a multitude of individual behaviours of electrons interacting with one another and with the surrounding ions. In the conditions of superconductivity quasi-particles have no longer charges and some Majorana quasi-particles have been recently discovered in superconducting nano-structures. (A.C.)
Original Title
Le spectre de Majorana
Source
14 refs.
Record Type
Journal Article
Journal
Reflets de la Physique; ISSN 1953-793X;
; (no.61); p. 4-10

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Sarazin, X, E-mail: sarazin@lal.in2p3.fr2015
AbstractAbstract
[en] This paper gives a review of the double beta experimental techniques and projects, in the search for the Majorana neutrino. The purpose of this review is to detail, for each technique, the different origins of background, how they can be identified, and how they can be reduced. Advantages and limitations of the different techniques are discussed
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1. Franco-Algerian workshop on neutrino physics; Constantine (Algeria); 22-23 Oct 2013; Available from http://dx.doi.org/10.1088/1742-6596/593/1/012006; Country of input: International Atomic Energy Agency (IAEA)
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Journal Article
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Conference
Journal
Journal of Physics. Conference Series (Online); ISSN 1742-6596;
; v. 593(1); [20 p.]

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AbstractAbstract
[en] We study the total and the geometric phase associated with neutrino mixing and we show that the phases produced by the neutrino oscillations have different values depending on the representation of the mixing matrix and on the neutrino nature. Therefore the phases represent a possible probe to distinguish between Dirac and Majorana neutrinos. (paper)
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Source
DICE2018: 9. International Workshop on Spacetime - Matter - Quantum Mechanics; Castiglioncello (Italy); 17-21 Sep 2018; Available from http://dx.doi.org/10.1088/1742-6596/1275/1/012053; Country of input: International Atomic Energy Agency (IAEA)
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Journal Article
Literature Type
Conference
Journal
Journal of Physics. Conference Series (Online); ISSN 1742-6596;
; v. 1275(1); [5 p.]

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Baranov, Mikhail; Cai, Z.; Hu, Y.; Zoller, P.
Joint Annual Meeting of the Austrian Physical Society and the Swiss Physical Society together with the Austrian and Swiss Societies for Astronomy and Astrophysics2015
Joint Annual Meeting of the Austrian Physical Society and the Swiss Physical Society together with the Austrian and Swiss Societies for Astronomy and Astrophysics2015
AbstractAbstract
No abstract available
Primary Subject
Source
Austrian Physical Society (Austria); Vienna University of Technology, Gusshausstraße 27-29, 1040 Vienna (Austria); 116 p; 2015; p. 77; Joint Annual Meeting of the Austrian Physical Society and the Swiss Physical Society together with the Austrian and Swiss Societies for Astronomy and Astrophysics; Gemeinsame Jahrestagung der Österreichischen Physikalischen Gesellschaft und der Schweizerischen Physikalischen Gesellschaft zusammen mit den Österreichischen und der Schweizerischen Gesellschaften für Astronomie und Astrophysik; Vienna (Austria); 1-4 Sep 2015; Available in abstract form only. Available from: https://www.oepg.at/index.php?page=meetings&subpage=abstracts&lang=de; Available from: Vienna University of Technology, Gusshausstraße 27-29, 1040 Vienna (AT)
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Miscellaneous
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Conference
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Herviou, Loic
Universite Paris-Saclay, Ecole doctorale no. 564 - Physique en Ile-de-France, Espace Technologique, Immeuble Discovery, Route de l'Orme aux Merisiers RD 128, 91190 Saint-Aubin (France); Ecole Polytechnique, CPHT (France)2017
Universite Paris-Saclay, Ecole doctorale no. 564 - Physique en Ile-de-France, Espace Technologique, Immeuble Discovery, Route de l'Orme aux Merisiers RD 128, 91190 Saint-Aubin (France); Ecole Polytechnique, CPHT (France)2017
AbstractAbstract
[en] In this thesis, we study theoretically different aspects of topological systems. These models present resilient properties due to a non-trivial topology of their band structures, and in particular exotic edge excitations such as Majorana fermions. Entanglement markers have been fundamental to the study of these systems and of gapless systems in general, but are challenging to measure. Bipartite charge fluctuations were proposed as a weak measurement of entanglement entropy. We extend results on standard Luttinger Liquids to generic families of one- and two-dimensional non-interacting topological systems. A volume law arises, and is linked to the Quantum Fisher information, with non-analyticities at the phase transitions. Critical points are characterized by universal coefficients that reveal the topological aspect of the transitions. In a second time, we include interactions and show that some of these signatures are preserved in interacting topological superconductors. Through analytical and numerical methods, we study two Coulomb-coupled topological superconducting wires. The interplay between unconventional superconductivity and strong interactions leads to exotic phases. We show the appearance of orbital currents spontaneously breaking the time-reversal symmetry, and of an unusual gapless phase that is the extension of two critical Majorana modes. Finally, we focus on electronic transport mediated by Majorana fermions. We study a floating superconducting island carrying several such impurities, a potential building block for a quantum computer. The Majorana fermions affect the statistics of the charge carriers, which leads to very resilient fractionalized transport. We extend previous studies to the charge degenerate case and map it to the Multi-Channel Kondo model at large interaction, reinterpreted in terms of a particle moving in a high-dimensional, dissipative lattice. (author)
[fr]
Dans cette these, nous etudions d'un point de vue theorique differents aspects de la matiere topologique. Ces systemes presentent des proprietes resistantes aux eventuelles perturbations grace a une topologie non-triviale de leur structure de bandes. Des excitations exotiques, par exemple des fermions de Majorana, peuvent apparaitre a leurs bords. L'etude des marqueurs d'intrication a ete fondamentale dans la comprehension de ces systemes, et des phases libres en general. 1 est cependant difficile de les mesurer. Les fluctuations de charge bipartites, permettant une mesure faible de l'intrication, ont ete proposees comme alternative. Nous generalisons les precedents travaux sur les Liquides de Luttinger a des familles generiques de supraconducteurs et isolants topologiques en une et deux dimensions. Les fluctuations suivent une loi de volume, liee a l'Information Quantique de Fisher et non-analytique aux transition de phase. Leurs points critiques sont caracterises par des coefficients universels, qui revelent leur topologie. Dans un second temps, nous considerons des systemes en interactions. Certaines des signatures des transitions topologiques survivent dans les supraconducteurs topologiques. Nous etudions ensuite le diagramme de phase de deux fils supraconducteurs couples par une interaction Coulombienne, presentant des phases exotiques grace a la competition avec la supraconductivite non-conventionnelle. Des courants orbitaux brisant spontanement la symetrie de renversement du temps peuvent apparaitre, ainsi qu'une phase de fermions libres, extension de deux chaines de Majorana critiques. Enfin, nous nous interessons aux effets des fermions de Majorana sur le transport electronique. Nous etudions un ilot supraconducteur ou plusieurs de ces fermions existent, pouvant etre l'un des composants elementaires d'un eventuel ordinateur quantique. Ces impuretes changent les statistiques des porteurs de charges, menant a une fractionalisation robuste de la conductance. Nous etendons les etudes precedentes au cas ou le nombre d'electrons dans la boite peut fluctuer, et montrons l'equivalence de ce probleme avec le modele Kondo a plusieurs canaux. Nous reinterpretons alors ce modele en terme du deplacement d'une particule dans un reseau fictif dissipatif. (auteur)Original Title
Phases topologiques et Fermions de Majorana
Primary Subject
Source
8 Sep 2017; 253 p; 299 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; These de doctorat de l'Universite Paris-Saclay
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Xiao, Jinpeng; An, Jin, E-mail: anjin@nju.edu.cn2015
AbstractAbstract
[en] We study the magnetic structures and their connections with topological superconductivity due to the proximity effect for coupled magnetic atomic chains deposited on a superconductor. Several magnetic phases are self-consistently determined, including both the coplanar and noncoplanar ones. For an N-chain triangular atomic ladder, topologically nontrivial superconducting states can always be realized, but strongly depend on its magnetic structure and the number of atomic chains. When N is even, the topologically nontrivial states with noncoplanar structures are characterized by invariants, while the topologically nontrivial noncoplanar states with an odd N are characterized by integer invariants, due to the presence of a new chiral symmetry. The new chiral symmetry for the noncoplanar states is found to be robust against the on-site disorder, as long as the crystal reflection symmetry is respected. (paper)
Source
Available from http://dx.doi.org/10.1088/1367-2630/17/11/113034; Country of input: International Atomic Energy Agency (IAEA)
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Journal Article
Journal
New Journal of Physics; ISSN 1367-2630;
; v. 17(11); [16 p.]

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Kauffman, Louis H.; Lomonaco, Samuel J., E-mail: kauffman@uic.edu, E-mail: lomonaco@umbc.edu2018
AbstractAbstract
[en] This paper is an introduction to relationships between topology, quantum computing, and the properties of Fermions. In particular, we study the remarkable unitary braid group representations associated with Majorana fermions.
Primary Subject
Source
Copyright (c) 2018 Springer Science+Business Media, LLC, part of Springer Nature; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA)
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Journal Article
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Quantum Information Processing (Print); ISSN 1570-0755;
; v. 17(8); p. 1-81

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