Publications

2024

• Cold atoms in two dimensional quasi crystals
  
  • Zhu Zhaoxuan
  , 2024. Quasicrystals are long-range-ordered solids without translational symmetry, showing rotational symmetries that are forbidden for normal crystals, for example 5 fold, 7 fold, 8 fold etc. Their discovery in the laboratory during the 1980s lead to a paradigm shift in crystallography, revolutionizing the basic idea on possible structure of solids.Since then on, quasicrystals have attracted much attentions, owing to their intriguing properties, including for examples phasonic quasiparticles, transport properties, intricate energy spectrum, nontrivial topological order and Anderson-like localization.A powerful tool to study the physical properties of quasicrystals is quantum simulation. With the realization of ultracold atomic systems in the 1990s and the rapid developments thereon, a new playground of quantum many body physics has opened. In particular, the strong control over the physical parameters and the various measurement tools in a cold atomic system make it a promising platform for quantum simulation.A one-dimensional quasiperiodic potential in cold atoms experiments can be created by superimposing several laser beams with incommensurable periods.In the past years, cold atoms in one-dimensional quasiperiodic potentials have been studied extensively. A two-dimensional optical lattice giving a quasicrystal potential can also be created by certain geometrical arrangements of laser beams. This was first proposed theoretically in 2005, and realized in cold atoms experiments in 2019 following a configuration proposed in 2013. Localization of weakly interacting bosons in that system has been reported.With these advancements in experiments, the theoretical studies of two dimensional cold atoms in quasicrystal potentials also start to gain momentum.In this thesis, we give a theoretical study of quantum simulation of two-dimensional quasicrystals with cold atoms. We discuss the single particle properties and the thermodynamic phase diagrams for two dimensional bosons in a shallow quasicrystal potential. (10.70675/f99ff7faz966cz487azbe2cz81efa45abf09)
  DOI : 10.70675/f99ff7faz966cz487azbe2cz81efa45abf09
• On energy and particle production in cosmology: the particular case of the gravitino
  
  • Casagrande Gabriele
  • Dudas Emilian
  • Peloso Marco
  , 2023. It is well-known that the number of particles produced in cosmology, commonly defined in the literature from the Fock space of the instantaneous hamiltonian of the canonically normalized fields, is ambiguous. On the other hand, the energy computed from the energy-momentum tensor should be physical. We compare the corresponding Fock spaces and relate them through a Bogolyubov transformation. We find that for particles of spin $0$, $1$ and $3/2$ the two Fock spaces are different, whereas they are the same for spin $1/2$ fermions. For spin $0$ and $1$, for particles of high momenta the two Fock spaces align, as intuitively expected. For the spin $3/2$, one finds two puzzles. The first one is that the two corresponding Fock spaces do not match even in the limit of high momenta. The second is that whereas we provide evidence for the equivalence theorem between longitudinal gravitinos and the goldstino in terms of an exact matching between the lagrangians and the instantaneous hamiltonians for the canonically normalized fields, the energy operator computed from the Rarita--Schwinger action does not seem to be captured in a simple way by the goldstino action. Our results suggest a re-analysis of non-thermal gravitino production in cosmology.
• Testing the Scalar Weak Gravity Conjecture in No-scale Supergravity
  
  • Dudas Emilian
  • Gherghetta Tony
  • Olive Keith A.
  • Verner Sarunas
  , 2023. We explore possible extensions of the Weak Gravity Conjecture (WGC) to scalar field theories. To avoid charged black hole remnants, the WGC requires the existence of a particle with a mass $m < g q M_P$, with charge $q$ and U(1) gauge coupling $g$, allowing the decay to shed the black hole charge. Although there is no obvious problem that arises in the absence of a U(1) charge, it has been postulated that gravity must remain the weakest force even when extended to scalar interactions. Quantifying this conjecture may be done by comparing scalar and gravitational amplitudes, or as we advocate here by comparing scattering cross sections. In theories with non-trivial field space geometries, by working out examples with perturbation theory around arbitrary field values and performing tadpole resummations, we argue that the conjecture must be applied only at the extrema of the scalar potential (when expressed in locally canonical coordinates). We consider several toy models in the context of no-scale supergravity and also consider examples of inflationary models.
• Scattering from an external field in quantum chromodynamics at high energies: from foundations to interdisciplinary connections
  
  • Angelopoulou Athanasia-Konstantina
  • Le Anh Dung
  • Munier Stéphane
  , 2023. We review the factorization of the $S$-matrix elements in the context of particle scattering off an external field, which can serve as a model for the field of a large nucleus. The factorization takes the form of a convolution of light cone wave functions describing the physical incoming and outgoing states in terms of bare partons, and products of Wilson lines. The latter represent the interaction between the bare partons and the external field. Specializing to elastic scattering amplitudes of onia at very high energies, we introduce the color dipole model, which formulates the calculation of the modulus-squared of the wave functions in quantum chromodynamics with the help of a branching random walk, and the scattering amplitudes as observables on this classical stochastic process. Methods developed for general branching processes produce analytical formulas for the asymptotics of such observables, and thus enable one to derive exact large-rapidity expressions for onium-nucleus cross sections, from which electron-nucleus cross sections may be inferred.
• Simple predictors of $T_c$ in superconducting cuprates reveal role of interactions between effective Wannier orbitals in the $d-p$ 3-band model
  
  • Vučičević Jakša
  • Ferrero Michel
  Physical Review B, American Physical Society, 2024, 109 (8), pp.L081115. At optimal doping, different cuprate compounds can exhibit vastly different critical temperatures for superconductivity ($T_c$), ranging from about 20 K to about 135 K. The precise properties of the lattice that determine the magnitude of the $T_c$ are currently unknown. In this paper, we investigate the dependence of the optimal doping $T_c$ on the parameters of the Emery ($d-p$) model for the CuO$_2$ planes in the cuprates. We show that the best scaling is obtained not with the parameters of the model written in the real ($d/p$-orbital) space, but rather written in the space of effective Wannier orbitals. In this basis, one obtains a model of three sublattices coupled through all possible 4-point interactions. We identify multiple predictor variables that fit the experimental $T_c$ to about $\pm4$ K and that depend on the coupling constants in the transformed Hamiltonian. (10.1103/PhysRevB.109.L081115)
  DOI : 10.1103/PhysRevB.109.L081115
• Saturation of fishbone instability through zonal flows driven by energetic particle transport in tokamak plasmas
  
  • Brochard G.
  • Liu C.
  • Wei X.
  • Heidbrink W.
  • Lin Z.
  • Falessi M.V.
  • Zonca F.
  • Qiu Z.
  • Gorelenkov N.
  • Chrystal C.
  • Du X.
  • Bao J.
  • Polevoi A.R.
  • Schneider M.
  • Kim S.H.
  • Pinches S.D.
  • Liu P.
  • Nicolau J.H.
  • Lütjens Hinrich
  , 2024, pp.016052. Gyrokinetic and kinetic-MHD simulations are performed for the fishbone instability in the DIII-D discharge #178631, chosen for validation of first-principles simulations to predict the energetic particle (EP) transport in an ITER prefusion baseline scenario. Fishbone modes are found to generate zonal flows, which dominate the fishbone saturation. The underlying mechanisms of the two-way fishbone-zonal flows nonlinear interplay are discussed in details. Numerical and analytical analyses identify the fishbone-induced EP redistribution as the dominant generation mechanism for zonal flows. The zonal flows modify the nonlinear dynamics of phase space zonal structures, which reduces the amount of EPs able to resonate with the mode, leading to an early fishbone saturation. Simulation results including zonal flows agree quantitatively with DIII-D experimental measurements of the fishbone saturation amplitude and EP transport, supporting this novel saturation mechanism by self-generated zonal flows. Moreover, the wave-particle mode-locking mechanism is shown to determine quantitatively the fishbone frequency down-chirping, as evident in GTC simulation results in agreement with predictions from analytical theory. Finally, the fishbone-induced zonal flows are possibly responsible for the formation of an ion-ITB in the DIII-D discharge. Based on the low EP transport and the large zonal flow shearing rates associated with the fishbone instability in gyrokinetic simulations of the ITER scenario, it is conjectured that high performance scenarios could be designed in ITER burning plasmas through fishbone-induced ITBs. (10.1088/1741-4326/ad8013)
  DOI : 10.1088/1741-4326/ad8013
• Saturation of Fishbone Instability by Self-Generated Zonal Flows in Tokamak Plasmas
  
  • Brochard G.
  • Liu C.
  • Wei X.
  • Heidbrink W.
  • Lin Z.
  • Gorelenkov N.
  • Chrystal C.
  • Du X.
  • Bao J.
  • Polevoi A. R.
  • Schneider M.
  • Kim S. H.
  • Pinches S. D.
  • Liu P.
  • Nicolau J. H.
  • Lütjens Hinrich
  Physical Review Letters, American Physical Society, 2024, 132 (7), pp.075101. (10.1103/PhysRevLett.132.075101)
  DOI : 10.1103/PhysRevLett.132.075101
• Doping-dependent charge- and spin-density wave orderings in a monolayer of Pb adatoms on Si(111)
  
  • Vandelli M.
  • Galler A.
  • Rubio A.
  • Lichtenstein A.
  • Biermann S.
  • Stepanov E.
  Npj Quantum Materials, Nature publishing, 2024, 9 (1), pp.19. Abstract In this work we computed the phase diagram as a function of temperature and doping for a system of lead adatoms allocated periodically on a silicon (111) surface. This Si(111):Pb material is characterized by a strong and long-ranged Coulomb interaction, a relatively large value of the spin-orbit coupling, and a structural phase transition that occurs at low temperature. In order to describe the collective electronic behavior in the system, we perform many-body calculations consistently taking all these important features into account. We find that charge- and spin-density wave orderings coexist with each other in several regions of the phase diagram. This result is in agreement with the recent experimental observation of a chiral spin texture in the charge density wave phase in this material. We also find that the geometries of the charge and spin textures strongly depend on the doping level. The formation of such a rich phase diagram in the Si(111):Pb material can be explained by a combined effect of the lattice distortion and electronic correlations. (10.1038/s41535-024-00630-w)
  DOI : 10.1038/s41535-024-00630-w
• Climate-Induced Economic Damages Can Lead to Private-Debt Tipping Points
  
  • Martin Hugo A.
  • Quiquet Aurélien
  • Nicolas T.
  • Giraud Gaël
  • Charbit Sylvie
  • Roche Didier M.
  , 2024. Designing climate change policies requires considering the feedback loops between mitigation and adaptation, since more mitigation efforts today will trigger lower adaptation costs. In this framework, carbon taxes are often seen as promising tools but at the risk of financially overburdening the private sector, depriving it of important economic resources. However, analyzing the financial feasibility of mitigation-adaptation policies using conventional Integrated Assessment Models (IAM) is limited, as they do not simultaneously endogenize economic growth, emissions, and damages. Here, we present IDEE (Integrated Dynamic Environment-Economic), a new IAM based on the coupling of an Earth Model of Intermediate Complexity and a non-linear macroeconomic model in continuous time. Then, we analyze the simultaneous effects of carbon taxes and public spending, both on climate and on the world economy. We show that, above a warming about +2.3°C, damages drastically foster the need for additional investments in productive capital—an adaptation necessity—that potentially leads private firms to a debt overhang and a worldwide cascade of defaults. This suggests that the Paris Agreement target should not only be motivated by the climatic non-linearities and tipping points arising beyond the +2°C threshold, but also by the emergence of financial tipping points. We also show that, provided public subsidies are high enough, a tax of USD 300 per tCO2e by 2030 enables reaching net-zero emissions in 2050, preventing firms from suffering global bankruptcy. We anticipate IDEE to be a starting point for a new class of IAMs that better represent the reciprocal feedback loops between the environment and the economy.
• Deconfinement transition within the Curci-Ferrari model -- Renormalization scale and scheme dependences
  
  • Surkau Victor Tomas Mari
  • Reinosa Urko
  , 2024, pp.094033. We analyze the confinement/deconfinement transition of pure Yang-Mills theories within the framework of the center-symmetric Landau gauge supplemented by a Curci-Ferrari mass term that models the effect of the associated Gribov copies in the infrared. In addition to providing details for earlier one-loop calculations in that framework, we explore how the results depend on the renormalization scale and/or on the renormalization scheme. We find that the predicted values for the transition temperatures of SU($2$) and SU($3$) Yang-Mills theories are similar in both schemes and are little sensitive to the renormalization scale $\mu$ over a wide range of values including the standard range $\smash{\mu\in[\pi T,4\pi T]}$. These values are also close both to those obtained from a minimal sensitivity principle and to those of lattice simulations, especially in the SU($3$) case. These results further confirm the good behavior of perturbative calculations within the Curci-Ferrari model and support the adequacy of the latter as an effective description of Yang-Mills theories in the infrared. We perform a similar analysis for the spinodal temperatures in the SU($3$) case and for the Polyakov loop, the order parameter associated to the breaking of center symmetry. (10.1103/PhysRevD.109.094033)
  DOI : 10.1103/PhysRevD.109.094033
• Strongly-correlated bosons in optical quasicrystals: Localization, fractality, and Bose-glass physics
  
  • Sanchez-Palencia Laurent
  , 2024.
• The surface counter-terms of the ϕ44 theory on the half space R+×R3
  
  • Borji Majdouline
  • Kopper Christoph
  Journal of Mathematical Physics, American Institute of Physics (AIP), 2024, 65 (2). In a previous work, we established perturbative renormalizability to all orders of the massive φ 4 4-theory on a half-space also called the semi-infinite massive φ 4 4-theory. Five counter-terms which are functions depending on the position in the space, were needed to make the theory finite. The aim of the present paper is to establish that for a particular choice of the renormalization conditions the effective action consists of a part which is independent of the boundary conditions (Dirichlet, Neumann and Robin) plus a boundary term in the case of the Robin and Neumann boundary conditions. The key idea of our method is the decomposition of the correlators into a bulk part, which is defined as the scalar field model on the full space R 4 with a quartic interaction restricted to the halfspace, plus a remainder which we call "the surface part". We analyse this surface part and establish perturbatively that the φ 4 4 theory in R + × R 3 is made finite by adding the bulk counter-terms and two additional counter-terms to the bare interaction in the case of Robin and Neumann boundary conditions. These surface counter-terms are position independent and are proportional to S φ 2 and S φ ∂ n φ. For Dirichlet boundary conditions, we prove that no surface counter-terms are needed and the bulk counter-terms are sufficient to renormalize the connected amputated (Dirichlet) Schwinger functions. A key technical novelty as compared to our previous work is a proof that the power counting of the surface part of the correlators is better by one scaling dimension than their bulk counterparts. (10.1063/5.0164178)
  DOI : 10.1063/5.0164178
• Strongly-correlated bosons in optical quasicrystals: Localization, fractality, and Bose- glass physics
  
  • Sanchez-Palencia Laurent
  , 2024.
• High-field magnetization of KEr ( MoO 4 ) 2
  
  • Kutko K.
  • Bernáth B.
  • Khrustalyov V.
  • Young O.
  • Engelkamp H.
  • Christianen P.
  • Prodan L.
  • Skourski Y.
  • Pourovskii L.
  • Khmelevskyi S.
  • Kamenskyi D.
  Physical Review B, American Physical Society, 2024, 109 (2), pp.024438. (10.1103/PhysRevB.109.024438)
  DOI : 10.1103/PhysRevB.109.024438
• Étudier la médiatisation de la Marche de 1983, un défi interdisciplinaire
  
  • Gebeil Sophie
  • Génois -Cpt Mathieu
  , 2024. Cette communication présente les travaux conduits dans le cadre du volet français du programme PICCH concernant la médiatisation audiovisuelle de la Marche pour l’égalité et contre le racisme de 1983. Je préciserai le contexte et les questionnements à l’origine de ce projet ainsi que les corpus mobilisés, notamment concernant les archives télévisuelles et web. Enfin, j’exposerai les enjeux méthodologiques et interdisciplinaires liés à l’utilisation de méthodes computationnelles à travers l’exemple du travail co-dirigé par P. Bellot, M. Génois et moi-même lors d’un stage réalisé à AMU en 2023. Mathieu Génois présentera ainsi l’apport méthodologique et technique en sciences de l’informatique.
• Valence-Ordered Thin-Film Nickelate with Tricomponent Nickel Coordination Prepared by Topochemical Reduction
  
  • Raji Aravind
  • Dong Zhengang
  • Porée Victor
  • Subedi Alaska
  • Li Xiaoyan
  • Mundet Bernat
  • Varbaro Lucia
  • Domínguez Claribel
  • Hadjimichael Marios
  • Feng Bohan
  • Nicolaou Alessandro
  • Rueff Jean-Pascal
  • Li Danfeng
  • Gloter Alexandre
  ACS Nano, American Chemical Society, 2024, 18 (5), pp.4077-4088. The metal-hydride-based "topochemical reduc-tion" process has produced several thermodynamically unstable phases across various transition metal oxide series with unusual crystal structures and nontrivial ground states. Here, by such an oxygen (de-)intercalation method we synthesis a samarium nickelate with ordered nickel valences associated with tri-component coordination configurations. This structure, with a formula of Sm 9 Ni 9 O 22 as revealed by four-dimensional scanning transmission electron microscopy (4D-STEM), emerges from the intricate planes of {303} pc ordered apical oxygen vacancies. X-ray spectroscopy measurements and ab initio calculations show the coexistence of square planar, pyramidal, and octahedral Ni sites with mono-, bi-, and tri-valences. It leads to an intense orbital polarization, charge-ordering, and a ground state with a strong electron localization marked by the disappearance of ligand-hole configuration at low temperature. This nickelate compound provides another example of previously inaccessible materials enabled by topotactic transformations and presents an interesting platform where mixed Ni valence can give rise to exotic phenomena. (10.1021/acsnano.3c07614)
  DOI : 10.1021/acsnano.3c07614
• Ascending the attractor flow in the D1-D5 system
  
  • Georgescu Silvia
  • Guica Monica
  • Kovensky Nicolas
  , 2024. We study maximally supersymmetric irrelevant deformations of the D1-D5 CFT that correspond to following the attractor flow in reverse in the dual half-BPS black string solutions of type IIB supergravity on K3. When a single, quadratic condition is imposed on the parameters of the 22 such irrelevant deformations, the asymptotics of the solution degenerate to a linear dilaton like spacetime. We identify each such degeneration limit with a known decoupling limit of string theory, which yields little string theory or deformations thereof (the so-called open brane LST, or ODp theories), compactified to two dimensions. This suggests that a 21-parameter family of the above deformations leads to UV-complete theories, which are string theories decoupled from gravity that are continuously connected to each other. All these theories have been argued to display Hagedorn behaviour; we show that including the F1 strings leads to an additional Cardy term. The resulting entropy formula closely resembles that of single-trace $T\bar T$-deformed CFTs, whose generalisations could provide possibly tractable effective two-dimensional descriptions of the above web of theories. We also consider the asymptotically flat black strings. At fixed temperature, the partition function is dominated by thermodynamically stable, small black string solutions, similar to the ones in the decoupled backgrounds. We show that certain asymptotic symmetries of these black strings bear a striking resemblance with the state-dependent symmetries of single-trace $T\bar T$, and break down precisely when the background solution reaches the large black string threshold. This suggests that small, asymptotically flat black strings may also admit a $T\bar T$ - like effective description.
• Magnetism and Metallicity in Moiré Transition Metal Dichalcogenides
  
  • Tscheppe Patrick
  • Zang Jiawei
  • Klett Marcel
  • Karakuzu Seher
  • Celarier Armelle
  • Cheng Zhengqian
  • Marianetti Chris
  • Maier Thomas
  • Ferrero Michel
  • Millis Andrew
  • Schäfer Thomas
  Proceedings of the National Academy of Sciences of the United States of America, National Academy of Sciences, 2024, 121 (3), pp.e2311486121. The ability to control the properties of twisted bilayer transition metal dichalcogenides in situ makes them an ideal platform for investigating the interplay of strong correlations and geometric frustration. Of particular interest are the low energy scales, which make it possible to experimentally access both temperature and magnetic fields that are of the order of the bandwidth or the correlation scale. In this manuscript we analyze the moiré Hubbard model, believed to describe the low energy physics of an important subclass of the twisted bilayer compounds. We establish its magnetic and the metal-insulator phase diagram for the full range of magnetic fields up to the fully spin polarized state. We find a rich phase diagram including fully and partially polarized insulating and metallic phases of which we determine the interplay of magnetic order, Zeeman-field, and metallicity, and make connection to recent experiments. (10.1073/pnas.2311486121)
  DOI : 10.1073/pnas.2311486121
• Bounds on photon scattering
  
  • Häring Kelian
  • Hebbar Aditya
  • Karateev Denis
  • Meineri Marco
  • Penedones João
  Journal of High Energy Physics, Springer, 2024, 2410, pp.103. We study 2-to-2 scattering amplitudes of massless spin one particles in $d=4$ space-time dimensions, like real world photons. We define a set of non-perturbative observables (Wilson coefficients) which describe these amplitudes at low energies. We use full non-linear unitarity to construct various novel numerical bounds on these observables. For completeness, we also rederive some bounds using positivity only. We discover and explain why some of these Wilson coefficients cannot be bounded. (10.1007/JHEP10(2024)103)
  DOI : 10.1007/JHEP10(2024)103
• Searching for a new light gauge boson with axial couplings in muon beam dump experiments
  
  • Fayet Pierre
  • Olea-Romacho María Olalla
  Journal of High Energy Physics, Springer, 2024, 2024 (07), pp.223. We present a formalism for new $U(1)$ interactions involving weak hypercharge, baryon, and lepton numbers, and a possible axial symmetry generator $F_A$ in the presence of a second Brout-Englert-Higgs doublet. The resulting $U$ boson, after mixing with the $Z$, interpolates between a generalised dark photon, a dark $Z$, and an axially coupled gauge boson. We especially focus on the axial couplings originating from $F_A$ or from mixing with the $Z$, determined by the scalar sector via parameters like $\tan\beta$ and the v.e.v. of an extra dark singlet. We explore the distinctive features of axially coupled interactions, especially in the ultrarelativistic limit, where the $U$ boson behaves much as an axion-like particle, with enhanced interactions to quarks and leptons. This enhancement is particularly relevant for future muon beam dump experiments, since the muon mass considerably increases the effective coupling, proportional to $2m_\mu/m_U$, compared to analogous experiments with electrons. We also analyse the shape of the expected beam dump exclusion or discovery regions, influenced by $U$ boson interactions and the experiment geometry. Different situations are considered, limited in particular by cases for which the $U$ decays before reaching the detector, or has too small couplings to produce detectable events. We also compare to vectorially coupled bosons and axion-like pseudoscalars, highlighting the importance of understanding the parameter space for future experiment design and optimisation. (10.1007/JHEP07(2024)223)
  DOI : 10.1007/JHEP07(2024)223
• On the Quantum Bousso Bound in de Sitter JT gravity
  
  • Franken Victor
  • Rondeau François
  Journal of High Energy Physics, Springer, 2024, 03, pp.178. We prove the validity of the Strominger-Thompson quantum Bousso bound in the infinite class of conformal vacua of de Sitter space in semiclassical JT gravity. The Bousso-Fisher-Leichenauer-Wall quantum Bousso bound follows from an analogous derivation, requiring only initial quantum non-expansion. In this process, we show that the quantity ${2\pi k^{\mu}k^{\nu}<:T_{\mu\nu}:>-S"-\frac{6}{c}(S')^2}$ vanishes in any vacuum state, entailing a stronger version of Wall's quantum null energy condition. We derive an entropy formula in the presence of a generic class of two reflecting boundaries, in order to apply our argument to the half reduction model of de Sitter JT gravity. (10.1007/JHEP03(2024)178)
  DOI : 10.1007/JHEP03(2024)178
• Orientation Memory of Magnetic Dipoles
  
  • Oblak Blagoje
  • Seraj Ali
  Physical Review D, American Physical Society, 2024, 109 (4), pp.044037. We study the precession caused by electromagnetic radiation on a magnetic dipole located far from the source. As we show, this entails a net rotation of the dipole in the plane orthogonal to the direction of wave propagation, providing an electromagnetic analogue of gyroscopic gravitational memory. Like its gravitational cousin, the precession rate falls off with the square of the distance to the source, and is related to electric-magnetic duality and optical helicity on the celestial sphere. We use a multipolar expansion to compute the memory effect due to localized sources such as moving point charges, and highlight its occurrence in setups that break parity symmetry. (10.1103/PhysRevD.109.044037)
  DOI : 10.1103/PhysRevD.109.044037
• Mechanical structure of the nucleon and the baryon octet
  
  • Won Ho-Yeon
  • Kim Hyun-Chul
  • Kim June-Young
  Journal of High Energy Physics, Springer, 2024, 05, pp.173. In this study, we investigate the flavor-decomposed gravitational form factors(GFFs) of the nucleon and the baryon octet in a mean-field approach based on the large $N_{c}$ limit of QCD. Our central focus lies on illuminating the distinctive role played by the separate quarks in this context. We first scrutinize the behavior of the gravitational form factors in the large $N_c$ limit, tracing the relations governed by spin-flavor symmetry within the framework of flavor SU(3). The results are compared with those in flavor SU(2). Additionally, we quantitatively assess the fraction of light-front momentum carried by individual quark flavors within the nucleon. Notably, we unravel variations arising from the mass distribution, as evidenced through the non-conserved form factor of the nucleon, known as the cosmological constant-term $\bar{c}(q^2)$. Venturing further, we explore not only the decomposition of the total angular momentum into the orbital angular momentum and intrinsic spin, but also its flavor decomposition. Furthermore, we delve into the intricate interplay between the $D$-term and $\bar{c}$ form factors, discerning their collaborative impact on the stabilization of the nucleon system. Alongside this, we undertake an analysis, questioning the assumption of "large $N_{c}$ blindness'' concerning $D^{u-d} \sim 0$. Our examination concludes that such an assumption finds justification predominantly within the framework of flavor SU(3) symmetry. Using the spin-flavor symmetry, the baryon octet GFFs can be easily obtained, and various sum rules between the baryon octet GFFs are discussed. Finally, we introduce the generalized electromagnetic form factors, where the flavor structure of the electromagnetic current is induced into the GFFs. Similar to the electromagnetic form factors, we find that these newly introduced form factors possess the $U$-spin symmetry. (10.1007/JHEP05(2024)173)
  DOI : 10.1007/JHEP05(2024)173
• Dynamic critical exponent in quantum long-range models
  
  • Benedetti Dario
  • Gurau Razvan
  • Lettera Davide
  Physical Review B, American Physical Society, 2024, 110 (10), pp.104102. Quantum long-range models at zero temperature can be described by fractional Lifshitz field theories, that is, anisotropic models whose actions are short-range in time and long-range in space. In this paper we study the renormalization of fractional Lifshitz field theories with weakly relevant cubic or quartic self-interactions. Their nontrivial infrared fixed points exhibit Lifshitz scale invariance, and we compute the lowest-order corrections to the dynamic critical exponent. (10.1103/PhysRevB.110.104102)
  DOI : 10.1103/PhysRevB.110.104102
• Impact of hole-doping on the thermoelectric properties of pyrite FeS2
  
  • Mukherjee Anustup
  • Subedi Alaska
  Solid State Communications, Elsevier, 2024, 406, pp.116194. We present a comprehensive first-principles analysis of the thermoelectric transport properties of hole-doped pyrite FeS$_2$ that includes electron-phonon interactions. This work was motivated by the observed variations in the magnitude of thermopower reported in previous experimental and theoretical studies of hole-doped FeS$_2$ systems. Our calculations reveal that hole-doped FeS$_2$ exhibits large positive room-temperature thermopower across all doping levels, with a room-temperature thermopower of 608 $μ$V/K at a low hole-doping concentration of 10$^{19}$ cm$^{-3}$. This promising thermopower finding prompted a comprehensive investigation of other key thermoelectric parameters governing the thermoelectric figure of merit $ZT$. The calculated electrical conductivity is modest and remains below 10$^5$ S/m at room-temperature for all doping levels, limiting the achievable power factor. Furthermore, the thermal conductivity is found to be phonon driven, with a high room-temperature lattice thermal conductivity of 40.5 W/mK. Consequently, the calculated $ZT$ remains below 0.1, suggesting that hole-doped FeS$_2$ may not a viable candidate for effective thermoelectric applications despite its promising thermopower. (10.1016/j.ssc.2025.116194)
  DOI : 10.1016/j.ssc.2025.116194