Publications

Order by: publication date number of citations

• Bulk locality from the celestial amplitude

  Chi-Ming Chang, Yu-tin Huang, Zi-Xun Huang, Wei Li

  SciPost Phys. 12, 176 (2022) · published 27 May 2022 | Toggle abstract · pdf

  In this paper, we study the implications of bulk locality on the celestial amplitude. In the context of the four-point amplitude, the fact that the bulk S-matrix factorizes locally in poles of Mandelstam variables is reflected in the imaginary part of the celestial amplitude. In particular, on the real axis in the complex plane of the boost weight, the imaginary part of the celestial amplitude can be given as a positive expansion on the Poincar\'e partial waves, which are nothing but the projection of flat-space spinning polynomials onto the celestial sphere. Furthermore, we derive the celestial dispersion relation, which relates the imaginary part to the residue of the celestial amplitude for negative even integer boost weight. The latter is precisely the projection of low energy EFT coefficients onto the celestial sphere. We demonstrate these properties explicitly on the open and closed string celestial amplitudes. Finally, we give an explicit expansion of the Poincar\'e partial waves in terms of 2D conformal partial waves.

  10 citations

• Adaptive numerical solution of Kadanoff-Baym equations

  Francisco Meirinhos, Michael Kajan, Johann Kroha, Tim Bode

  SciPost Phys. Core 5, 030 (2022) · published 27 May 2022 | Toggle abstract · pdf

  A time-stepping scheme with adaptivity in both the step size and the integration order is presented in the context of non-equilibrium dynamics described via Kadanoff-Baym equations. The accuracy and effectiveness of the algorithm are analysed by obtaining numerical solutions of exactly solvable models. We find a significant reduction in the number of time-steps compared to fixed-step methods. Due to the at least quadratic scaling of Kadanoff-Baym equations, reducing the amount of steps can dramatically increase the accessible integration time, opening the door for the study of long-time dynamics in interacting systems. A selection of illustrative examples is provided, among them interacting and open quantum systems as well as classical stochastic processes. An open-source implementation of our algorithm in the scientific-computing language Julia is made available.

  8 citations

• Out-of-equilibrium dynamics of the Kitaev model on the Bethe lattice via coupled Heisenberg equations

  Oleksandr Gamayun, Oleg Lychkovskiy

  SciPost Phys. 12, 175 (2022) · published 25 May 2022 | Toggle abstract · pdf

  The Kitaev model on the honeycomb lattice, while being integrable via the spin-fermion mapping, has generally resisted an analytical treatment of the far-from-equilibrium dynamics due to the extensive number of relevant configurations of conserved charges. Here we study a close proxy of this model, the isotropic Kitaev spin-$1/2$ model on the Bethe lattice. Instead of relying on the spin-fermion mapping, we take a straightforward approach of solving Heisenberg equations for a tailored subset of spin operators. The simplest operator in this subset corresponds to the energy contribution of a single bond direction. As an example, we calculate the time-dependent expectation value of this observable for a factorized translation-invariant (or staggered-translation-invariant) initial state with arbitrary initial (staggered) polarization.

  1 citation

• Logarithmic, noise-induced dynamics in the Anderson insulator

  Talía L. M. Lezama, Yevgeny Bar Lev

  SciPost Phys. 12, 174 (2022) · published 25 May 2022 | Toggle abstract · pdf

  We study the dynamical behavior of the one-dimensional Anderson insulator in the presence of a local noise. We show that the noise induces logarithmically slow energy and entanglement growth, until the system reaches an infinite-temperature state, where both quantities saturate to extensive values. The saturation value of the entanglement entropy approaches the average entanglement entropy over all possible product states. At infinite temperature, we find that a density excitation spreads logarithmically with time, without any signs of asymptotic diffusive behavior. In addition, we provide a theoretical picture which qualitatively reproduces the phenomenology of particle transport.

  13 citations

• (Inter)racialisation: the regulation of domestic and urban space in housing North-African migrants in 1960s and 1970s France

  Rébecca Suzanne Franco

  Mig. Pol. 1, 003 (2022) · published 25 May 2022 | Toggle abstract · pdf

  Literature on immigrant housing and assimilation has shown how housing policies perpetuate, create and contest racial boundaries. This paper argues for the necessity to look at the regulation of domestic space together with the regulation of the urban space. By reading “along” and “against” the archival grain, this paper looks at housing policies that targeted the North-African migrant population in the 1960s and 1970s in France as colonial continuities. French authorities ostensibly encouraged gendered assimilation through spatial politics and interventions in the domestic space. Literature on the French context has shown how this perpetuated racialisation in the housing process. Building upon feminist scholarship on gender, intimacy, and colonialism, this paper shows how these policies did not acknowledge interracialised households and prevented interracialised intimacies. This helps understand how housing policies can reinforce racialised exclusion by regulating racial boundaries in the urban space and the domestic space together.

• Fingerprints of hot-phonon physics in time-resolved correlated quantum lattice dynamics

  Emmanuele Cappelluti, Dino Novko

  SciPost Phys. 12, 173 (2022) · published 24 May 2022 | Toggle abstract · pdf

  The time dynamics of the energy flow from electronic to lattice degrees of freedom in pump-probe setups could be strongly affected by the presence of a hot-phonon bottleneck, which can sustain longer coherence of the optically excited electronic states. Recently, hot-phonon physics has been experimentally observed and theoretically described in MgB$_2$, the electron-phonon based superconductor with $T_{\rm c}\approx 39$ K. By employing a combined ab-initio and quantum-field-theory approach and by taking MgB$_2$ as an example, here we propose a novel path for revealing the presence and characterizing the properties of hot phonons through a direct analysis of the information encoded in the lattice inter-atomic correlations. Such method exploits the underlying symmetry of the $E_{2g}$ hot modes characterized by a out-of-phase in-plane motion of the two boron atoms. Since hot phonons occur typically at high-symmetry points of the Brillouin zone, with specific symmetries of the lattice displacements, the present analysis is quite general and it could aid in revealing the hot-phonon physics in other promising materials, such as graphene, boron nitride, or black phosphorus.

  3 citations

• Argyres-Douglas theories in class S without irregularity

  Christopher Beem, Wolfger Peelaers

  SciPost Phys. 12, 172 (2022) · published 24 May 2022 | Toggle abstract · pdf

  We make a preliminary investigation into twisted $A_{2n}$ theories of class S. Contrary to a common piece of folklore, we establish that theories of this type realise a variety of models of Argyres-Douglas type while utilising only regular punctures. We present an in-depth analysis of all twisted $A_2$ trinion theories, analyse their interrelations via partial Higgsing, and discuss some of their generalised S-dualities.

  9 citations

• Audible axions with a booster: Stochastic gravitational waves from rotating ALPs

  Eric Madge, Wolfram Ratzinger, Daniel Schmitt, Pedro Schwaller

  SciPost Phys. 12, 171 (2022) · published 24 May 2022 | Toggle abstract · pdf

  Gravitational waves provide a novel way to probe axions or axion-like particles coupled to a dark photon field, even in the absence of couplings to Standard Model particles. In the conventional misalignment mechanism, the generation of an observable stochastic gravitational wave background, however, requires large axion decay constants. We here investigate the gravitational wave signal generated within the kinetic misalignment scenario, where the axion is assumed to have a large initial velocity. Its kinetic energy then provides a sufficiently high energy budget to generate a detectable gravitational wave signal also at lower values of the decay constant. We obtain an analytic estimate as well as perform numerical simulations of the corresponding gravitational wave signal, and evaluate its detectability at current and future gravitational wave observatories. We further present the corresponding projected constraints on the parameter space of the model, along with the parameter regions in which the dark photon or axion constitute dark matter, or in which the baryon asymmetry of the Universe is generated via the axiogenesis mechanism. Finally we compute the GW production from the fragmentation of rotating axions, which is however difficult to observe experimentally.

  16 citations

• Hidden conformal symmetries from Killing towers with an application to large-D/CFT

  Cynthia Keeler, Victoria Martin, Alankrita Priya

  SciPost Phys. 12, 170 (2022) · published 23 May 2022 | Toggle abstract · pdf

  We generalize the notion of hidden conformal symmetry in Kerr/CFT to Kerr-(A)dS black holes in arbitrary dimensions. We build the SL(2, R) generators directly from the Killing tower, whose Killing tensors and Killing vectors enforce the separability of the equations of motion. Our construction amounts to an explicit relationship between hidden conformal symmetries and Killing tensors: we use the Killing tower to build a novel tensor equation connecting the SL(2,R) Casimir with the radial Klein-Gordon operator. For asymptotically flat black holes in four and five dimensions we recover previously known results that were obtained using the "near-region" limit and the monodromy method. We then perform a monodromy evaluation of the Klein-Gordon scalar wave equation for all Kerr-(A)dS black holes, finding explicit forms for the zero mode symmetry generators. We also extend this analysis to the large-dimensional Schwarzschild black hole as a step towards buliding a Large-D/CFT correspondence.

  4 citations

• New directions in the search for dark matter

  Surjeet Rajendran

  SciPost Phys. Lect. Notes 56 (2022) · published 23 May 2022 | Toggle abstract · pdf

  The identification of the nature of dark matter is one of the most important problems confronting particle physics. Current observational constraints permit the mass of the dark matter to range from $\sim 10^{-22}$ eV - $10^{48}$ GeV. Given the weak nature of these bounds and the ease with which dark matter models can be constructed, it is clear that the problem can only be solved experimentally. In these lectures, I discuss methods to experimentally probe a wide range of dark matter candidates.

  3 citations