Publications

Order by: publication date number of citations

• Twisted S-duality

  Surya Raghavendran, Philsang Yoo

  SciPost Phys. 19, 049 (2025) · published 20 August 2025 | Toggle abstract · pdf

  We study an $\mathrm{SL}(2, \mathbb{Z})$ symmetry of a variant of BCOV theory in three complex dimensions. Using conjectural descriptions of twists of superstrings in terms of topological strings, we argue that this action can be thought of as a version of S-duality that preserves an $\mathrm{SU}(3)$-invariant twist of type IIB supergravity. We analyze how $\mathrm{SL}(2, \mathbb{Z})$ acts on various deformations of the holomorphic-topological twist of 4-dimensional $\mathcal{N}=4$ supersymmetric gauge theory, which come from residual supertranslations and superconformal symmetries, and are of relevance to geometric Langlands theory and gauge-theoretic constructions of the Yangian.

• Quantum chaos in PT symmetric quantum systems

  Kshitij Sharma, Himanshu Sahu, Subroto Mukerjee

  SciPost Phys. 19, 120 (2025) · published 7 November 2025 | Toggle abstract · pdf

  In this study, we explore the interplay between $\mathcal{PT}$-symmetry and quantum chaos in a non-Hermitian dynamical system. We consider an extension of the standard diagnostics of quantum chaos, namely the complex level spacing ratio and out-of-time-ordered correlators (OTOCs), to study the $\mathcal{PT}$-symmetric quantum kicked rotor model. The kicked rotor has long been regarded as a paradigmatic dynamic system to study classical and quantum chaos. By introducing non-Hermiticity in the quantum kicked rotor, we uncover new phases and transitions that are absent in the Hermitian system. From the study of the complex level spacing ratio, we locate three regimes – one which is integrable and $\mathcal{PT}$-symmetry, another which is chaotic with $\mathcal{PT}$-symmetry and a third which is chaotic but with broken $\mathcal{PT}$-symmetry. We find that the complex level spacing ratio can distinguish between all three phases. Since calculations of the OTOC can be related to those of the classical Lyapunov exponent in the semi-classical limit, we investigate its nature in these regimes and at the phase boundaries. In the phases with $\mathcal{PT}$-symmetry, the OTOC exhibits behaviour akin to what is observed in the Hermitian system in both the integrable and chaotic regimes. Moreover, in the $\mathcal{PT}$-symmetry broken phase, the OTOC demonstrates additional exponential growth stemming from the complex nature of the eigenvalue spectrum at later times. We derive the analytical form of the late-time behaviour of the OTOC. By defining a normalized OTOC to mitigate the effects caused by $\mathcal{PT}$-symmetry breaking, we show that the OTOC exhibits singular behaviour at the transition from the $\mathcal{PT}$-symmetric chaotic phase to the $\mathcal{PT}$-symmetry broken, chaotic phase.

• ATLAS results on charmonium production

  Vato Kartvelishvili

  SciPost Phys. Proc. 8, 014 (2022) · published 11 July 2022 | Toggle abstract · pdf

  An overview is given of the results on charmonium production obtained by the ATLAS collaboration at the LHC. Recent preliminary measurements covering prompt and non-prompt production of $J/\psi$ and $\psi(2S)$ states in the range of high transverse momenta from 60 to 360~GeV are highlighted.

• $\Lambda$ Polarizing Fragmentation Function from Belle $e^+ e^-$ data

  Umberto D'Alesio, Francesco Murgia, Marco Zaccheddu

  SciPost Phys. Proc. 8, 131 (2022) · published 13 July 2022 | Toggle abstract · pdf

  Experimental data from Belle Collaboration for the transverse polarization of $\Lambda$'s measured in $e^+ e^-$ annihilation processes are used to extract the polarizing fragmentation function (FF) within a TMD approach. We consider both associated and inclusive $\Lambda$ production, showing a quite consistent scenario. Good separation in flavor is obtained, leading to four independent FFs. Predictions for SIDIS processes at the EIC, crucial for understanding their universality and evolution properties, are also presented.

• Breaking Standard Model global symmetries with the tau lepton

  Jorge Portolés

  SciPost Phys. Proc. 16, 010 (2025) · published 14 July 2025 | Toggle abstract · pdf

  Properties of the dynamics of the Standard Model processes such as lepton flavour preservation and lepton, or baryon, number conservation, are usually taken for granted. The only reason is that it seems that these non-gauge accidental symmetries of the Standard Model seem to be conserved in Nature with great accuracy. In addition, the coupling of lepton doublets to the electroweak gauge bosons is universal and does not depend on the flavour. The discovery of the non-zero mass of the neutrinos and, maybe, the hints coming from the B-anomalies at LHCb, point out to a different scenario. I will briefly summarize some aspects of these contingent symmetries as seen from tau lepton processes.

• Highlights of the results from the GRAPES-3 experiment

  Hariharan Balakrishnan, S. Ahmad, M. Chakraborty, S.R. Dugad, U.D. Goswami, S.K. Gupta, Y. Hayashi, P. Jagadeesan, A. Jain, P. Jain, S. Kawakami, H. Kojima, S. Mahapatra, P.K. Mohanty, R. Moharana, Y. Muraki, P.K. Nayak, T. Nonaka, A. Oshima, D. Pattanaik, B.P. Pant, M. Rameez, K. Ramesh, L.V. Reddy, S. Shibata, F. Varsi, M. Zuberi

  SciPost Phys. Proc. 13, 021 (2023) · published 28 September 2023 | Toggle abstract · pdf

  The GRAPES-3 experiment is a unique, extensive air shower experiment consisting of 400 scintillator detectors spread over 25000 m$^2$ and a 560 m$^2$ muon telescope. The experiment located at Ooty, India, has been collecting data for the past two decades. The unique capabilities of GRAPES-3 have allowed the study of cosmic rays over energies from a few TeV to tens of PeV and beyond. The measurement of the directional flux of muons (E$_\mu$≥1 GeV) by the large muon telescope permits an excellent gamma-hadron separation, which then becomes a powerful tool in the study of multi-TeV gamma-ray sources and the composition of primary cosmic rays. However, the high precision measurements also enable studies of transient atmospheric and interplanetary phenomena such as those produced by thunderstorms and geomagnetic storms. This paper presents some exciting new and recent results, including updates on various ongoing analyses.

• Magnetic, electronic, and structural investigation of the strongly correlated Y$_{1-x}$Sm$_{x}$Co$_5$ system

  F. Passos, D. Cornejo, G. J. Nilsen, V. Martelli, J. Larrea Jiménez

  SciPost Phys. Proc. 11, 021 (2023) · published 6 June 2023 | Toggle abstract · pdf

  SmCo$_5$ and YCo$_5$ are isostructural compounds both showing large magnetocrystalline anisotropy, where the former originates mainly from the crystal-electric field and magnetic interactions. We investigate the contribution of both interactions by partially substituting Y by Sm in as-cast polycrystalline Y$_{1-x}$Sm$_{x}$Co$_5$ (with $x$=0.00, 0.12, 0.18, 0.31, and 0.40) and measuring their structural, magnetic, and electrical properties through X-ray diffraction, magnetization, and electrical transport measurements. Our results suggest an interplay between microstructure strain in as-cast samples and the electronic and magnetic interactions.

• Calculation of asymptotic normalization coefficients in the complex-ranged Gaussian basis

  Dinmukhamed A. Sailaubek, Olga A. Rubtsova

  SciPost Phys. Proc. 3, 043 (2020) · published 27 February 2020 | Toggle abstract · pdf

  A new technique towards finding asymptotic normalization coefficients in the complex-ranged Gaussian basis is presented. It is shown that a diagonalisation procedure for the total Hamiltonian matrix in the given basis results in approximation for a radial part of the bound state wave function from the origin up to the far asymptotic distances, which allows to extract ANCs rather accurately. The method is illustrated by calculations of single-particle ANCs for nuclei bound states in cases of non-local nucleon-nucleus interactions, in particular, phenomenological global potentials with the Perey-Buck's non-locality.

• Asymptotic T-duality in three dimensions

  Stéphane Detournay, José Figueroa, Alejandro Vilar López

  SciPost Phys. 19, 044 (2025) · published 18 August 2025 | Toggle abstract · pdf

  In (super)gravity theories, T-duality relates solutions with an exact isometry which can have wildly different asymptotic behaviors: A well-known example is the duality between BTZ black holes and (non-extremal) three-dimensional black strings. Using this dual pair, we show how the knowledge of a phase space which includes one set of solutions (here, BTZ black holes embedded in the Brown-Henneaux phase space) allows to obtain a phase space for the dual set via an asymptotic notion of T-duality. The resulting asymptotic symmetry algebras can be very different. For our particular example, we find a large algebra of symmetries for the black string phase space which includes as subalgebras $\mathfrak{bms}_2$, $\mathfrak{bms}_3$, and a twisted warped conformal algebra. On the way, we show that a chiral half of the Brown-Henneaux boundary conditions are dual to the Compère-Song-Strominger ones.

• Topology-induced symmetry breaking demonstrated in antiferromagnetic magnons on a Möbius strip

  Kuangyin Deng, Ran Cheng

  SciPost Phys. 19, 048 (2025) · published 19 August 2025 | Toggle abstract · pdf

  We propose a mechanism of topology-induced symmetry breaking, where certain local symmetry preserved by the Hamiltonian is explicitly broken in the eigenmodes of excitation due to nontrivial real-space topology. We demonstrate this phenomenon by studying magnonic excitations on a Möbius strip comprising two antiferromagnetically coupled spin chains. Even with a simple Hamiltonian respecting local rotational symmetry, with all local curvature effects ignored, magnons exhibit linear polarization of the Néel vector devoid of chirality, forming two non-degenerate branches that cannot be smoothly connected to nor globally decomposed into, the circularly-polarized magnons. Correspondingly, one branch undergoes a spectral shift and only admits standing waves of half-integer wavelength, whereas the other only affords standing waves of integer wavelength. Under the Möbius boundary condition, we further identify an exotic phase hosting spontaneous antiferromagnetic order whilst all exchange couplings are ferromagnetic. The suppression of chirality in the order parameter dynamics, hence the pattern of standing waves, can be generalized to other elementary excitations on non-orientable surfaces. Our findings showcase the profound influence of real-space topology on the physical nature of not just the ground state but also the quasiparticles.