Publications

Order by: publication date number of citations

• Mixed QCD-electroweak corrections to $Z$ and $W$ boson production and their impact on the $W$ mass measurements at the LHC

  Arnd Behring

  SciPost Phys. Proc. 7, 003 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We report on recently computed mixed QCD-electroweak corrections to on-shell $W$ and $Z$ boson production. We use these differential predictions to estimate their impact on the $W$ boson mass determination at the LHC.

• Double Virtual Contributions for Massless 2 -> 3 Scattering in NNLO QCD

  Vasily Sotnikov

  SciPost Phys. Proc. 7, 002 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We review the recent advances in the calculation of two-loop QCD corrections for massless five-point scattering that paved the way for their broad phenomenological applications in calculation of NNLO QCD predictions. We first discuss the construction of a transcendental function basis which facilitates derivation of compact analytic representations for two-loop amplitudes and enables their fast and stable numerical evaluation over physical phase space. We then present the recent calculations of the leading-color two-loop corrections for hadroproduction of three photons and three jets.

  1 citation

• Master integrals contributing to two-loop leading colour QCD helicity amplitudes for top-quark pair production in the gluon fusion channel

  Ekta Chaubey

  SciPost Phys. Proc. 7, 001 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We discuss the analytic structure of the master integrals relevant for computing the com- plete set of leading-colour analytic helicity amplitudes for top-quark pair production via gluon fusion at two loops in QCD. This includes corrections due to massive fermion loops which give rise to integrals involving elliptic curves. We also elaborate on the structure of singularities that play an important role in the numerical evaluation of the iterated integrals and their analytic continuation.

  1 citation

• CrystalNets.jl: Identification of Crystal Topologies

  Lionel Zoubritzky, François-Xavier Coudert

  SciPost Chem. 1, 005 (2022) · published 17 June 2022 | Toggle abstract · pdf

  We present here an open-source Julia library for the topological identification of crystalline materials, with algorithmic and computational improvements over the previously available software in the field, resulting in a speed increase of one order of magnitude. This new algorithm and implementation can therefore be used at large scale in high-throughput screening methodologies. We have validated and benchmarked CrystalNets.jl against a diverse set of crystal databases, covering in particular metal–organic frameworks, aluminophosphates, zeolites, and other inorganic compounds.

  8 citations

• Edge physics at the deconfined transition between a quantum spin Hall insulator and a superconductor

  Ruochen Ma, Liujun Zou, Chong Wang

  SciPost Phys. 12, 196 (2022) · published 14 June 2022 | Toggle abstract · pdf

  We study the edge physics of the deconfined quantum phase transition (DQCP) between a spontaneous quantum spin Hall (QSH) insulator and a spin-singlet superconductor (SC). Although the bulk of this transition is in the same universality class as the paradigmatic deconfined Neel to valence-bond-solid transition, the boundary physics has a richer structure due to proximity to a quantum spin Hall state. We use the parton trick to write down an effective field theory for the QSH-SC transition in the presence of a boundary. We calculate various edge properties in an $N\to\infty$ limit. We show that the boundary Luttinger liquid in the QSH state survives at the phase transition, but only as "fractional" degrees of freedom that carry charge but not spin. The physical fermion remains gapless on the edge at the critical point, with a universal jump in the fermion scaling dimension as the system approaches the transition from the QSH side. The critical point could be viewed as a gapless analogue of the quantum spin Hall state but with the full $SU(2)$ spin rotation symmetry, which cannot be realized if the bulk is gapped.

  6 citations

• Entanglement entropy in quantum spin chains with broken parity number symmetry

  Arash Jafarizadeh, M. A. Rajabpour

  SciPost Phys. 12, 195 (2022) · published 14 June 2022 | Toggle abstract · pdf

  Consider a generic quantum spin chain that can be mapped to free quadratic fermions via Jordan-Wigner (JW) transformation. In the presence of arbitrary boundary magnetic fields, this Hamiltonian is no longer a quadratic Hamiltonian after JW transformation. Using ancillary sites and enlarging the Hamiltonian we first introduce a bigger quadratic Hamiltonian. Then we diagonalize this enlarged Hamiltonian in its most generic form and show that all the states are degenerate because of the presence of a zero mode. The eigenstates of the original spin chain with boundary magnetic fields can be derived after appropriate projection. We study in-depth the properties of the eigenstates of the enlarged Hamiltonian. In particular, we find: 1) the eigenstates in configuration bases, 2) calculate all the correlation functions, 3) find the reduced density matrices, 4) calculate the entanglement entropy. We show that the generic eigenstate of the enlarged Hamiltonian (including the eigenstates of the original spin chain) breaks the parity number symmetry and consequently one needs to take care of some technicalities regarding the calculation of the reduced density matrix and entanglement entropy. Interestingly we show that the entanglement structure of these eigenstates is quite universal and independent of the Hamiltonian. We support our results by applying them to a couple of examples.

  3 citations

• Laughable borders: Making the case for the humorous in migration studies

  Anja K. Franck

  Mig. Pol. 1, 004 (2022) · published 14 June 2022 | Toggle abstract · pdf

  Humor is widely recognized as a fundamental aspect of the human experience, that has also played a vital role in the way marginalized groups comment on and mock power. Yet, in migration research the methodological and analytical value of humor has been largely overlooked. Rather, migration studies has commonly centered its analysis around suffering and tragedy and, in the process, depicted migrant trajectories as endeavors largely devoid of laughter, humor, irony and play. This article suggests that such humorless representations of the migration process – and indeed of the migrant subject itself – has broader implications for the types of knowledge that we (re)produce around migrants’ experiences, subjectivities and struggles. In fact, it argues that migration studies’ failure to recognize migrants as humorous individuals risks feeding into processes of exceptionalization and de-humanization through setting “the migrant” up as an obscure figure that lacks “essentially human” qualities. In order to make the case for the humorous in migration research, the article illustrates how refugees arriving to the Greek island of Lesvos in the early summer of 2015 laughed at their own predicament as well as the technologies put in place to control their freedom of movement and how their laughter, humor and comic displays did important political work in refusing subjugation, in speaking truth to power and in capturing the absurdity of the violence that they faced.

  5 citations

• Rényi entropies and negative central charges in non-Hermitian quantum systems

  Yi-Ting Tu, Yu-Chin Tzeng, Po-Yao Chang

  SciPost Phys. 12, 194 (2022) · published 13 June 2022 | Toggle abstract · pdf

  Quantum entanglement is one essential element to characterize many-body quantum systems. However, the entanglement measures are mostly discussed in Hermitian systems. Here, we propose a natural extension of entanglement and R\'enyi entropies to non-Hermitian quantum systems. There have been other proposals for the computation of these quantities, which are distinct from what is proposed in the current paper. We demonstrate the proposed entanglement quantities which are referred to as generic entanglement and R\'enyi entropies. These quantities capture the desired entanglement properties in non-Hermitian critical systems, where the low-energy properties are governed by the non-unitary conformal field theories (CFTs). We find excellent agreement between the numerical extrapolation of the negative central charges from the generic entanglement/R\'enyi entropy and the non-unitary CFT prediction. Furthermore, we apply the generic entanglement/R\'enyi entropy to symmetry-protected topological phases with non-Hermitian perturbations. We find the generic $n$-th R\'enyi entropy captures the expected entanglement property, whereas the traditional R\'enyi entropy can exhibit unnatural singularities due to its improper definition.

  16 citations

• Real-time ab initio description of the photon-echo mechanisms in extended systems: the case study of bulk GaAs

  Marco D'Alessandro, Davide Sangalli

  SciPost Phys. 12, 193 (2022) · published 13 June 2022 | Toggle abstract · pdf

  In this paper we present an ab initio real-time analysis of free polarization decay and photon echo in extended systems. As a prototype material, we study bulk GaAs driven by ultra-short laser pulses of 10 fs (energy spread of 0.4 eV), with frequency tuned in the continuum of the optical spectrum. We compute the electronic polarization P(t), and define a computational procedure to extract the echo signal in the dipole approximation. Results are obtained in both the low and high field regime, and compared with a two-levels system (TLS) model, with parameters extracted from the ab initio simulations. ab initio results are in optimal agreement with the TLS in the low-field case, whereas some differences are observed in the high-field regime where the multi-band nature of GaAs becomes relevant. In the high field regime we compute the pulse area, and look for fluences with pulse area close to {\pi}. We highlight that such fluences are well below the damage threshold of GaAs. However a unique value of the area cannot be defined, due to the strong dependence of the transition dipoles in the energy window excited by the laser pulse.

• Page curves and bath deformations

  Elena Caceres, Arnab Kundu, Ayan K. Patra, Sanjit Shashi

  SciPost Phys. Core 5, 033 (2022) · published 13 June 2022 | Toggle abstract · pdf

  We study the black hole information problem within a semiclassically gravitating AdS$_d$ black hole coupled to and in equilibrium with a $d$-dimensional thermal conformal bath. We deform the bath state by a relevant scalar deformation, triggering a holographic RG flow whose “trans-IR” region deforms from a Schwarzschild geometry to a Kasner universe. The setup manifests two independent scales which control both the extent of coarse-graining and the entanglement dynamics when counting Hawking degrees of freedom in the bath. In tuning either, we find nontrivial changes to the Page time and Page curve. We consequently view the Page curve as a probe of the holographic RG flow, with a higher Page time manifesting as a result of increased coarse-graining of the bath degrees of freedom.

  17 citations