Publications

2020

• Tachyon condensation in magnetic compactifications
  
  • Buchmuller Wilfried
  • Dudas Emilian
  • Tatsuta Yoshiyuki
  , 2020. Intersecting D-brane models and their T-dual magnetic compactifications provide an attractive framework for particle physics, allowing for chiral fermions and supersymmetry breaking. Generically, magnetic compactifications have tachyons that are usually removed by Wilson lines. However, quantum corrections prevent local minima for Wilson lines. We therefore study tachyon condensation in the simplest case, the magnetic compactification of type I string theory on a torus to eight dimensions. We find that tachyon condensation restores supersymmetry, which is broken by the magnetic flux, and we compute the mass spectrum of vector- and hypermultiplets. The gauge group $\text{SO}(32)$ is broken to $\text{USp}(16)$. We give arguments that the vacuum reached by tachyon condensation corresponds to the unique 8d superstring theory already known in the literature, with discrete $B_{ab}$ background or, in the T-dual version, the type IIB orientifold with three $\text{O}7_-$-planes, one $\text{O}7_+$-plane and eight D7-branes coincident with the $\text{O}7_+$-plane. The ground state after tachyon condensation is supersymmetric and has no chiral fermions.
• Nonlinear Spectroscopy of Collective Modes in an Excitonic Insulator
  
  • Golež Denis
  • Sun Zhiyuan
  • Murakami Yuta
  • Georges Antoine
  • Millis Andrew
  Physical Review Letters, American Physical Society, 2020, 125 (25), pp.257601. The nonlinear optical response of an excitonic insulator coupled to lattice degrees of freedom is shown to depend in strong and characteristic ways on whether the insulating behavior originates primarily from electron-electron or electron-lattice interactions. Linear response optical signatures of the massive phase mode and the amplitude (Higgs) mode are identified. Upon nonlinear excitation resonant to the phase mode, a new in-gap mode at twice the phase mode frequency is induced, leading to a huge second harmonic response. Excitation of in-gap phonon modes leads to different and much smaller effects. A Landau-Ginzburg theory analysis explains these different behaviors and reveals that a parametric resonance of the strongly excited phase mode is the origin of the photoinduced mode in the electron-dominant case. The difference in the nonlinear optical response serves as a measure of the dominant mechanism of the ordered phase. (10.1103/PhysRevLett.125.257601)
  DOI : 10.1103/PhysRevLett.125.257601
• On concentration inequalities for equilibrium states in lattice and symbolic dynamical systems
  
  • Moles Jordan
  , 2020. This thesis deals with the existence of Gaussian concentration for sufficiently mixing equilibrium states for lattice systems. Moreover, we show that such a property ensures uniqueness.In the first chapter, we show that if an equilibrium state associated to a shift-invariant and absolutely summable potential satisfies a Gaussian concentration bound then it is à fortiori mixing and unique em i.e. there is no phase transition.Thereafter, We study numerically a particular physical model which allows phase transition to occur: the ferromagnetic Ising model in two dimensions. We evaluate concentration constants through classical estimates at all temperature. Thank to the behavior of these parameters, we emphasize divergence of the Gaussian concentration constant at the critical temperature deduce that such property doesn't hold.Later on, we prove that the Gaussian concentration behavior holds for all temperature above the critical one for this model.Then, we dedicate a chapter to the study of an unidimensional symbolic dynamics on a finite alphabet: chains with complete connections. In particular, we study the concentration properties of a unique equilibrium state associated to a potential (or transition probability) satisfying Walters' condition.In the end, we review the high-noise regime in probabilistic cellular automata. In particular, we prove that in this regime, the probabilistic cellular automata satisfies a Gaussian concentration for a certain class of spatio-temporal observables. (10.70675/ac2422e1za412z4271zafa9z1c42a1752a60)
  DOI : 10.70675/ac2422e1za412z4271zafa9z1c42a1752a60
• Quasi-many-body localization of interacting fermions with long-range couplings
  
  • Thomson S J
  • Schiró M
  Physical Review Research, American Physical Society, 2020, 2. A number of experimental platforms for quantum simulations of disordered quantum matter, from dipolar systems to trapped ions, involve degrees of freedom which are coupled by power-law decaying hoppings or interactions, yet the interplay of disorder and interactions in these systems is far less understood than in their short-ranged counterpart. Here, we consider a prototype model of interacting fermions with disordered longranged hoppings and interactions and use the flow equation approach to map out its dynamical phase diagram as a function of hopping and interaction exponents. We demonstrate that the flow equation technique is ideally suited to problems involving long-range couplings due to its ability to accurately simulate very large system sizes. We show that at large on-site disorder and for short-range interactions, a transition from a delocalized phase to a quasi-many-body localized (MBL) phase exists as the hopping range is decreased. This quasi-MBL phase is characterized by intriguing properties such as a set of emergent conserved quantities which decay algebraically with distance. Surprisingly, we find that a crossover between delocalized and quasi-MBL phases survives even in the presence of long-range interactions. (10.1103/physrevresearch.2.043368)
  DOI : 10.1103/physrevresearch.2.043368
• Global symmetries, hidden sectors and emergent (dark) vector interactions
  
  • Betzios P.
  • Kiritsis E.
  • Niarchos V.
  • Papadoulaki O.
  Journal of High Energy Physics, Springer, 2020, 2020 (12), pp.53. A bstract Hidden theories coupled to the SM may provide emergent (dark) vectors, that are composites/bound-states of the hidden fields. This is motivated by paradigms emerging from the AdS/CFT correspondence but it is a more general phenomenon. We explore the general setup and find that UV interactions among currents or charged fields give rise to emergent vectors in the IR. We study the general properties of such vectors and argue that they can be generically different from fundamental dark photons that have been studied so far. (10.1007/JHEP12(2020)053)
  DOI : 10.1007/JHEP12(2020)053
• Nonlinear dynamics of the fishbone-induced alpha transport on ITER
  
  • Brochard G.
  • Dumont R.
  • Lütjens H.
  • Garbet X.
  • Nicolas Thimothée
  • Maget P.
  Nuclear Fusion, IOP Publishing, 2020, 60 (12), pp.126019. (10.1088/1741-4326/abb14b)
  DOI : 10.1088/1741-4326/abb14b
• Efficient One-Loop-Renormalized Vertex Expansions with Connected Determinant Diagrammatic Monte Carlo
  
  • Šimkovic Fedor
  • Rossi Riccardo
  • Ferrero Michel
  Physical Review B, American Physical Society, 2020, 102 (19), pp.195122. We present a technique that enables the evaluation of perturbative expansions based on one-loop-renormalized vertices up to large expansion orders. Specifically, we show how to compute large-order corrections to the random phase approximation in either the particle-hole or particle-particle channels. The algorithm's efficiency is achieved by the summation over contributions of all symmetrized Feynman diagram topologies using determinants, and by integrating out analytically the two-body long-range interactions in order to yield an effective zero-range interaction. Notably, the exponential scaling of the algorithm as a function of perturbation order leads to a polynomial scaling of the approximation error with computational time for a convergent series. To assess the performance of our approach, we apply it to the nonperturbative regime of the square-lattice fermionic Hubbard model away from half-filling and report, as compared to the bare interaction expansion algorithm, significant improvements of the Monte Carlo variance as well as the convergence properties of the resulting perturbative series. (10.1103/PhysRevB.102.195122)
  DOI : 10.1103/PhysRevB.102.195122
• Tachyon condensation in magnetic compactifications
  
  • Buchmuller Wilfried
  • Dudas Emilian
  • Tatsuta Yoshiyuki
  , 2020. Intersecting D-brane models and their T-dual magnetic compactifications provide an attractive framework for particle physics, allowing for chiral fermions and supersymmetry breaking. Generically, magnetic compactifications have tachyons that are usually removed by Wilson lines. However, quantum corrections prevent local minima for Wilson lines. We therefore study tachyon condensation in the simplest case, the magnetic compactification of type I string theory on a torus to eight dimensions. We find that tachyon condensation restores supersymmetry, which is broken by the magnetic flux, and we compute the mass spectrum of vector- and hypermultiplets. The gauge group $\text{SO}(32)$ is broken to $\text{USp}(16)$. We give arguments that the vacuum reached by tachyon condensation corresponds to the unique 8d superstring theory already known in the literature, with discrete $B_{ab}$ background or, in the T-dual version, the type IIB orientifold with three $\text{O}7_-$-planes, one $\text{O}7_+$-plane and eight D7-branes coincident with the $\text{O}7_+$-plane. The ground state after tachyon condensation is supersymmetric and has no chiral fermions.
• Perturbative aspects of the deconfinement transition -- Physics beyond the Faddeev-Popov model
  
  • Reinosa Urko
  , 2020. In the case of non-abelian gauge theories, the standard Faddeev-Popov (FP) gauge-fixing procedure in the Landau gauge is known to be incomplete due to the presence of gauge-equivalent field configurations. A widespread belief is that the proper analysis of the low energy properties in this gauge requires the extension of the gauge-fixing procedure beyond the FP recipe. This manuscript reviews various applications of the Curci-Ferrari (CF) model, a phenomenological proposal for such an extension, based on the decoupling properties of Landau gauge correlators as computed on the lattice. We investigate the predictions of the model concerning the deconfinement transition of strongly interacting matter at finite temperature, first in the case of pure Yang-Mills theory and then in the case of heavy-quark Quantum Chromodynamics. We show that most qualitative aspects and also many quantitative features of the deconfinement transition can be accounted for within the CF model, with only one additional parameter, adjusted from comparison to lattice simulations. Moreover, these features emerge in a systematic and controlled perturbative expansion, as opposed to the ill-defined perturbative expansion within the FP model in the infrared. Applications at finite temperature and/or density require one to consider a background extension of the Landau gauge, the so-called Landau-deWitt gauge. The manuscript is also intended as a thorough but pedagogical introduction to these techniques, including the rationale for introducing a background, the role of the Weyl chambers, and the complications that emerge due to the sign problem in the case of a real quark chemical potential. It also investigates the fate of the correlation functions as computed in the CF model and conjectures a specific behavior for the corresponding functions evaluated on the lattice, in the case of the SU(2) gauge group.
• Renormalized perturbation theory at large expansion orders
  
  • Rossi Riccardo
  • Šimkovic Fedor
  • Ferrero M.
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2020, 132 (1), pp.11001. We present a general formalism that allows for the computation of large-order renormalized expansions, effectively doubling the numerically attainable perturbation order of renormalized Feynman diagrams. We show that this formulation compares advantageously to the currently standard techniques due to its high efficiency, simplicity, and broad range of applicability. Our formalism permits to easily complement perturbation theory with non-perturbative information, which we illustrate by implementing expansions renormalized by the addition of a gap or the inclusion of Dynamical Mean-Field Theory. As a result, we present numerically exact results for the square-lattice hole-doped Fermi-Hubbard model in the low-temperature non-Fermi-liquid regime, relevant to study the pseudogap of cuprate superconductors, and show the momentum-dependent suppression of fermionic excitations in the antinodal region. (10.1209/0295-5075/132/11001)
  DOI : 10.1209/0295-5075/132/11001
• Optical properties of LaNiO3 films tuned from compressive to tensile strain
  
  • Ardizzone I.
  • Zingl M.
  • Teyssier J.
  • Strand H.
  • Peil O.
  • Fowlie J.
  • Georgescu A.
  • Catalano S.
  • Bachar N.
  • Kuzmenko A.
  • Gibert M.
  • Triscone J.-M.
  • Georges A.
  • van der Marel D.
  Physical Review B, American Physical Society, 2020, 102 (15), pp.155148. Materials with strong electronic correlations host remarkable—and technologically relevant—phenomena such as magnetism, superconductivity, and metal-insulator transitions. Harnessing and controlling these effects is a major challenge, on which key advances are being made through lattice and strain engineering in thin films and heterostructures, leveraging the complex interplay between electronic and structural degrees of freedom. Here we show that the electronic structure of La⁢Ni⁢O3 can be tuned by means of lattice engineering. We use different substrates to induce compressive and tensile biaxial epitaxial strain in La⁢Ni⁢O3 thin films. Our measurements reveal systematic changes of the optical spectrum as a function of strain and, notably, an increase of the low-frequency free carrier weight as tensile strain is applied. Using density functional theory (DFT) calculations, we show that this apparently counterintuitive effect is due to a change of orientation of the oxygen octahedra. The calculations also reveal drastic changes of the electronic structure under strain, associated with a Fermi surface Lifshitz transition. We provide an online applet to explore these effects. The experimental value of integrated spectral weight below 2 eV is significantly (up to a factor of 3) smaller than the DFT results, indicating a transfer of spectral weight from the infrared to energies above 2 eV. The suppression of the free carrier weight and the transfer of spectral weight to high energies together indicate a correlation-induced band narrowing and free carrier mass enhancement due to electronic correlations. Our findings provide a promising avenue for the tuning and control of quantum materials employing lattice engineering. (10.1103/PhysRevB.102.155148)
  DOI : 10.1103/PhysRevB.102.155148
• Strongly-correlated one-dimensional bosons in continuous and quasiperiodic potentials
  
  • Yao Hepeng
  , 2020. In this thesis, we investigate the properties of one-dimensional bosons in various types of systems, focusing on the phase transitions or crossovers between different quantum degeneracy regimes. Combining quantum Monte Carlo with other standard techniques such as exact diagonalization and thermal Bethe ansatz, we can compute the behavior of 1D bosons in different cases where the results are still lacking. First, in the case of harmonically trapped continuous bosons, we provide a full characterization of a quantity called Tan's contact. By computing the universal scaling function of it, we identify the behavior of the contact in various regimes of degeneracy for 1D bosons. We show that the contact exhibits a maximum versus temperature and that it is a signature of the crossover to fermionization in the strongly-interacting regime. Secondly, we study the localization and fractal properties of 1D ideal gases in shallow quasiperiodic potentials. The quasiperiodic system provides an appealing intermediate between long-range ordered and genuine disordered systems with unusual critical properties. While the tight-binding Aubry-Andr'e (AA) model has been widely studied, the shallow lattice case behaves differently. We determine the critical localization properties of the system, the critical potential, mobility edges and critical exponents which are universal. Moreover, we calculate the fractal dimension of the energy spectrum and find it is non-universal but always smaller than unity, which shows the spectrum is nowhere dense. Finally, we move to the study of the interacting case. With the quantum Monte Carlo calculations, we compute the phase diagram of Lieb-Liniger bosons in shallow quasiperiodic potentials. A Bose glass, surrounded by superfluid and Mott phases, is found. At finite temperature, we show that the melting of the Mott lobes is characteristic of a fractal structure and find that the Bose glass is robust against thermal fluctuations up to temperatures accessible in experiments. (10.70675/4fc8d5edzab6cz4aa7zabddzb50578158cd8)
  DOI : 10.70675/4fc8d5edzab6cz4aa7zabddzb50578158cd8
• Statistics of the number of records for random walks and Lévy flights on a 1D lattice
  
  • Mounaix Philippe
  • Majumdar Satya
  • Schehr Grégory
  Journal of Physics A: Mathematical and Theoretical, IOP Publishing, 2020, 53 (41), pp.415003. We study the statistics of the number of records R n for a symmetric, n-step, discrete jump process on a 1D lattice. At a given step, the walker can jump by arbitrary lattice units drawn from a given symmetric probability distribution. This process includes, as a special case, the standard nearest neighbor lattice random walk. We derive explicitly the generating function of the distribution P (R n) of the number of records, valid for arbitrary discrete jump distributions. As a byproduct, we provide a relatively simple proof of the generalized Sparre Andersen theorem for the survival probability of a random walk on a line, with discrete or continuous jump distributions. For the discrete jump process, we then derive the asymptotic large n behavior of P (R n) as well as of the average number of records E(R n). We show that unlike the case of random walks with symmetric and continuous jump distributions where the record statistics is strongly universal (i.e., independent of the jump distribution for all n), the record statistics for lattice walks depends on the jump distribution for any fixed n. However, in the large n limit, we show that the distribution of the scaled record number R n /E(R n) approaches a universal, half-Gaussian form for any discrete jump process. The dependence on the jump distribution enters only through the scale factor E(R n), which we also compute in the large n limit for arbitrary jump distributions. We present explicit results for a few examples and provide numerical checks of our analytical predictions. (10.1088/1751-8121/abac97)
  DOI : 10.1088/1751-8121/abac97
• Long-range multi-scalar models at three loops
  
  • Benedetti Dario
  • Gurau Razvan
  • Harribey Sabine
  • Suzuki Kenta
  Journal of Physics A: Mathematical and Theoretical, IOP Publishing, 2020, 53 (44), pp.445008. We compute the three-loop beta functions of long-range multi-scalar models with general quartic interactions. The long-range nature of the models is encoded in a kinetic term with a Laplacian to the power 0 < ζ < 1, rendering the computation of Feynman diagrams much harder than in the usual short-range case (ζ = 1). As a consequence, previous results stopped at two loops, while seven-loop results are available for short-range models. We push the renormalization group analysis to three loops, in an ϵ = 4ζ − d expansion at fixed dimension d < 4, extensively using the Mellin–Barnes representation of Feynman amplitudes in the Schwinger parametrization. We then specialize the beta functions to various models with different symmetry groups: O(N), , and O(N) × O(M). For such models, we compute the fixed points and critical exponents. (10.1088/1751-8121/abb6ae)
  DOI : 10.1088/1751-8121/abb6ae
• Crossed beam energy transfer between optically smoothed laser beams in inhomogeneous plasmas
  
  • Hüller Stefan
  • Raj Gaurav
  • Luo Mufei
  • Rozmus Wojciech
  • Pesme Denis
  Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Royal Society, The, 2020. Crossed beam energy transfer, CBET, in high-intensity laser plasma interaction is investigated for the case of optically smoothed laser beams. In the two approaches to laser-driven inertial confinement fusion (ICF) experiments, the direct-drive and the indirect-drive, CBET is of great importance because it governs the coupling of laser energy to the plasma. We use the two-dimensional wave-coupling code Harmony to simulate the transfer between two laser beams with speckle structure that overlap in a plasma with an inhomogeneous flow profile. We compare the CBET dynamics for laser beams with spatial incoherence and with spatio-temporal incoherence; in particular we apply the smoothing techniques using random phase plates (RPP) and smoothing by spectral dispersion (SSD), respectively. It is found that for laser beams (wave length λ0) with intensities (IL) above IL ∼ 2 × 10 15 W cm −2 (λ0/0.35µm) −2 (Te/keV), both the so-called plasma-induced smoothing as well as self-focusing in intense laser speckles induce temporal incoherence; the latter affects the CBET and the angular distribution of the light transmitted behind the zone of beam overlap. For RPP-smoothed incident beams, the resulting band width of the transmitted light can already be of the same order as the effective band width of the SSD available at major laser facilities. We examine the conditions when spatio-temporal smoothing techniques become efficient for CBET. (10.1098/rsta.2020.0038)
  DOI : 10.1098/rsta.2020.0038
• Models and data analysis tools for the Solar Orbiter mission
  
  • Rouillard A.
  • Pinto R F
  • Vourlidas A.
  • de Groof A.
  • Thompson W T
  • Bemporad A.
  • Dolei S
  • Indurain M.
  • Buchlin Eric
  • Sasso C
  • Spadaro D
  • Dalmasse K.
  • Hirzberger J
  • Zouganelis I.
  • Strugarek Antoine
  • Brun A S
  • Alexandre M.
  • Berghmans D.
  • Raouafi N E
  • Wiegelmann T.
  • Pagano P
  • Arge C N
  • Nieves-Chinchilla T
  • Lavarra M.
  • Poirier N.
  • Amari T.
  • Aran A.
  • Andretta V.
  • Antonucci E
  • Anastasiadis A
  • Auchère F.
  • Rubio L Bellot
  • Nicula B.
  • Bonnin X.
  • Bouchemit M.
  • Budnik E.
  • Caminade S.
  • Cecconi B.
  • Carlyle J
  • Cernuda I
  • Davila J.
  • Etesi L
  • Lara F Espinosa
  • Fedorov A.
  • Fineschi S.
  • Fludra A.
  • Genot V.
  • Georgoulis M K
  • Gilbert H R
  • Giunta A
  • Gomez-Herrero R
  • Guest S.
  • Haberreiter M.
  • Hassler D
  • Henney C J
  • Howard R A
  • Horbury T.
  • Janvier M.
  • Jones S I
  • Kozarev K
  • Kraaikamp E
  • Kouloumvakos A
  • Krucker S
  • Lagg A
  • Linker J.
  • Lavraud B.
  • Louarn P.
  • Maksimovic M
  • Maloney S.
  • Mann G.
  • Masson A.
  • Muller D.
  • Önel H
  • Osuna P.
  • Orozco Suarez D
  • Owen C J
  • Papaioannou A
  • Pérez-Suárez D
  • Rodriguez-Pacheco J
  • Parenti S.
  • Pariat E.
  • Peter H
  • Plunkett S
  • Pomoell J
  • Raines J M
  • Riethmuller T.
  • Rich N
  • Rodriguez L
  • Romoli M.
  • Sanchez L
  • Solanki S K
  • St Cyr O C
  • Straus T
  • Susino R.
  • Teriaca L.
  • del Toro Iniesta J C
  • Ventura R
  • Verbeeck C.
  • Vilmer Nicole
  • Warmuth A
  • Walsh A.
  • Watson C
  • Williams D
  • Wu Y
  • Zhukov A N
  Astronomy & Astrophysics - A&A, EDP Sciences, 2020. Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in-situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk. Aims. The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency (ESA)'s Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies. Methods. Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter. Results. This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission. Conclusions. The ongoing community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission. (10.1051/0004-6361/201935305)
  DOI : 10.1051/0004-6361/201935305
• Topological Majorana fermions models and new applications
  
  • Yang Fan
  , 2020. We present a theoretical study of topological models hosting Majorana fermion which is its own anti-particle, with relevant probe of quantum entanglement and experimental protocol for quantum engineering in cQED. In the first part, by proximity effects we address the topological superconducting wire systems, where Majorana fermions emerge as zero-energy modes at edges. By varying strengths of inter-wire couplings and changing fluxes of orbital magnetic fields, we show an interplay between topological p-wave superconductivity and quantum Hall states. For the remaining two parts of the thesis, we focus on Kitaev spin liquids that can be exactly solved in a Majorana fermion representation. We introduce valence bond fluctuations to characterize phase transitions between Abelian and non-Abelian phases, and find a general relation with the entanglement entropy. To simulate these many-body Majorana states, we propose a driven superconducting box circuit with generalizations to coupled box ensembles. There, a variety of models can be implemented including the toric code, the random Ising chain as well as the SYK Majorana model. (10.70675/7fac0383ze2cdz44b5z9e3az03d03c277671)
  DOI : 10.70675/7fac0383ze2cdz44b5z9e3az03d03c277671
• Liouville theory and matrix models: a Wheeler DeWitt perspective
  
  • Betzios P.
  • Papadoulaki O.
  Journal of High Energy Physics, Springer, 2020, 2020 (9), pp.125. A bstract We analyse the connections between the Wheeler DeWitt approach for two dimensional quantum gravity and holography, focusing mainly in the case of Liouville theory coupled to c = 1 matter. Our motivation is to understand whether some form of averaging is essential for the boundary theory, if we wish to describe the bulk quantum gravity path integral of this two dimensional example. The analysis hence, is in a spirit similar to the recent studies of Jackiw-Teitelboim (JT)-gravity. Macroscopic loop operators define the asymptotic region on which the holographic boundary dual resides. Matrix quantum mechanics (MQM) and the associated double scaled fermionic field theory on the contrary, is providing an explicit “unitary in superspace” description of the complete dynamics of such two dimensional universes with matter, including the effects of topology change. If we try to associate a Hilbert space to a single boundary dual, it seems that it cannot contain all the information present in the non-perturbative bulk quantum gravity path integral and MQM. (10.1007/JHEP09(2020)125)
  DOI : 10.1007/JHEP09(2020)125
• Coulomb logarithm accuracy in a Yukawa potential
  
  • Mora P.
  Physical Review E, American Physical Society (APS), 2020, 102 (3), pp.033206. (10.1103/PhysRevE.102.033206)
  DOI : 10.1103/PhysRevE.102.033206
• New opportunities at the photon energy frontier
  
  • Adam Jaroslav
  • Aidala Christine
  • Angerami Aaron
  • Audurier Benjamin
  • Bertulani Carlos
  • Bierlich Christian
  • Blok Boris
  • Brandenburg James Daniel
  • Brodsky Stanley
  • Bylinkin Aleksandr
  • Canoa Roman Veronica
  • Celiberto Francesco Giovanni
  • Cepila Jan
  • Chachamis Grigorios
  • Cole Brian
  • Contreras Guillermo
  • d'Enterria David
  • Dumitru Adrian
  • Fernández Téllez Arturo
  • Frankfurt Leonid
  • Gay Ducati Maria Beatriz
  • Geurts Frank
  • Gil da Silveira Gustavo
  • Giuli Francesco
  • Goncalves Victor P.
  • Grabowska-Bold Iwona
  • Guzey Vadim
  • Harland-Lang Lucian
  • Hentschinski Martin
  • Hobbs Timothy J.
  • Jalilian-Marian Jamal
  • Khoze Valery A.
  • Kim Yongsun
  • Klein Spencer R.
  • Knapen Simon
  • Kłusek-Gawenda Mariola
  • Krelina Michal
  • Kryshen Evgeny
  • Lappi Tuomas
  • Loizides Constantin
  • Luszczak Agnieszka
  • Machado Magno
  • Mäntysaari Heikki
  • Martins Daniel
  • Mcnulty Ronan
  • Murray Michael
  • Nemchik Jan
  • Noronha-Hostler Jacquelyn
  • Nystrand Joakim
  • Papa Alessandro
  • Pire Bernard
  • Ploskon Mateusz
  • Przybycien Marius
  • Ralston John P.
  • Rebello Teles Patricia
  • Royon Christophe
  • Schenke Björn
  • Schmidke William
  • Seger Janet
  • Stasto Anna
  • Steinberg Peter
  • Strikman Mark
  • Szczurek Antoni
  • Szymanowski Lech
  • Tapia Takaki Daniel
  • Ulrich Ralf
  • Villalobos Baillie Orlando
  • Vogt Ramona
  • Wallon Samuel
  • Winn Michael
  • Xie Keping
  • Xu Zhangbu
  • Yang Shuai
  • Zhalov Mikhail
  • Zhou Jian
  , 2020. Ultra-peripheral collisions (UPCs) involving heavy ions and protons are the energy frontier for photon-mediated interactions. UPC photons can be used for many purposes, including probing low-x gluons via photoproduction of dijets and vector mesons, probes of beyond-standard-model processes, such as those enabled by light-by-light scattering, and studies of two-photon production of the Higgs.
• Two-point functions of Neumann–Dirichlet open-string sector moduli
  
  • Coudarchet Thibaut
  • Partouche Hervé
  , 2021, 36 (34n35), pp.2141008. (10.1142/S0217751X21410086)
  DOI : 10.1142/S0217751X21410086
• Local quench spectroscopy of many-body quantum systems
  
  • Villa L.
  • Despres J.
  • Thomson S. J
  • Sanchez-Palencia L.
  Physical Review A, American Physical Society, 2020, 102 (3). Quench spectroscopy is a relatively new method which enables the investigation of spectral properties of many-body quantum systems by monitoring the out-of-equilibrium dynamics of real-space observables after a quench. So far the approach has been devised for global quenches or using local engineering of momentum-resolved excitations. Here, we extend the quench spectroscopy method to local quenches. We show that it allows us to extract quantitative information about global properties of the system, and in particular the elementary excitation spectrum. Using state-of-the-art numerical methods, we simulate the out-of-equilibrium dynamics of a variety of quantum systems following various local quench protocols and demonstrate a general scheme for designing an appropriate local quench protocol for any chosen model. We provide detailed examples of how the local quench protocol can be realised in realistic current generation experiments, including ultracold atomic gases and trapped ion systems. (10.1103/PhysRevA.102.033337)
  DOI : 10.1103/PhysRevA.102.033337
• An analytic model for the collisional transport and poloidal asymmetry distribution of impurities in tokamak plasmas
  
  • Maget Patrick
  • Manas Pierre
  • Frank Judith
  • Nicolas Timothée
  • Agullo Olivier
  • Garbet Xavier
  Plasma Physics and Controlled Fusion, IOP Publishing, 2020, 62, pp.105001. The coupling between the poloidal distribution and the collisional flux of impurities can be exploited to derive a simplified analytical model covering toroidal rotation and electrostatic potential asymmetry effects, valid in the Pfirsh-Schlüter regime. This model is compared with earlier works and with the drift-kinetic code NEO, which includes the full Fokker-Planck collision operator. The low computational cost of the model, compared to NEO, is particularly adapted for fast integrated simulation purposes. (10.1088/1361-6587/aba7f9)
  DOI : 10.1088/1361-6587/aba7f9
• Electronic correlations and transport in iron at Earth’s core conditions
  
  • Pourovskii L. V
  • Mravlje J.
  • Pozzo M.
  • Alfè D.
  Nature Communications, Nature Publishing Group, 2020, 11. The transport properties of iron under Earth's inner core conditions are essential input for the geophysical modelling but are poorly constrained experimentally. Here we show that the thermal and electrical conductivity of iron at those conditions remains high even if the electron-electron-scattering (EES) is properly taken into account. This result is obtained by ab initio simulations taking into account consistently both thermal disorder and electronic correlations. Thermal disorder suppresses the non-Fermi-liquid behavior of the bodycentered cubic iron phase, hence, reducing the EES; the total calculated thermal conductivity of this phase is 220 Wm −1 K −1 with the EES reduction not exceeding 20%. The EES and electron-lattice scattering are intertwined resulting in breaking of the Matthiessen's rule with increasing EES. In the hexagonal close-packed iron the EES is also not increased by thermal disorder and remains weak. Our main finding thus holds for the both likely iron phases in the inner core. (10.1038/s41467-020-18003-9)
  DOI : 10.1038/s41467-020-18003-9
• Orthorhombic-to-monoclinic transition in Ta 2 NiSe 5 due to a zone-center optical phonon instability
  
  • Subedi Alaska
  Physical Review Materials, American Physical Society, 2020, 4 (8). (10.1103/PhysRevMaterials.4.083601)
  DOI : 10.1103/PhysRevMaterials.4.083601