Tue·Oct 4, 2022Tuesday·October 4, 2022

1. 01*

   New Tools for Dissecting the General 2HDM

   Henning Bahl🇺🇸 · Marcela Carena🇺🇸 · Nina M. Coyle🇺🇸 · Aurora Ireland🇺🇸 · Carlos E.M. Wagner🇺🇸

   Two Higgs doublet models (2HDM) provide the low energy effective field theory (EFT) description in many well motivated extensions of the Standard Model. It is therefore relevant to study their properties, as well as the theoretical constraints on these models. In this article we concentrate on three relevant requirements for the validity of the 2HDM framework, namely the perturbative unitarity bounds, the bounded from below constraints, and the vacuum stability constraints. In this study, we concentrate on the most general renormalizable version of the 2HDM -- without imposing any parity symmetry, which may be violated in many UV extensions. We derive novel analytical expressions that generalize those previously obtained in more restrictive scenarios to the most general case. We also discuss the phenomenological implications of these bounds, focusing on CP violation.

   hep-phJHEP(2023)·23 citations
2. 02*

   Probing Ultra-light Primordial Black Holes as a Dark Matter Candidate

   Anupam Ray🇮🇳

   Dark Matter (DM) is omnipresent in our universe. Despite its abundance, the microscopic identity of DM still remains a mystery. Primordial black holes (PBHs), possibly formed via gravitational collapse of large density perturbations in the early universe, are one of the earliest proposed and viable DM candidates. Recent studies indicate that PBHs can make up a large or even entire fraction of the DM density for a wide range of masses. Here, we briefly review the observational constraints on PBHs as DM, concentrating on the ultra-light mass window. Ultra-light PBHs emit particles via Hawking radiation and can be probed by observing such Hawking evaporated particles in various space as well as ground based detectors. We also outline how next-generation gamma ray telescopes can set a stringent exclusion limit on ultra-light PBH DM by probing low energy photons.

   hep-phSpringer Proc.Phys.(2022)·0 citations
3. 03*

   How to Identify Different New Neutrino Oscillation Physics Scenarios at DUNE

   Peter B. Denton🇺🇸 · Alessio Giarnetti🇮🇹 · Davide Meloni🇮🇹

   Next generation neutrino oscillation experiments are expected to measure the remaining oscillation parameters with very good precision. They will have unprecedented capabilities to search for new physics that modify oscillations. DUNE, with its broad band beam, good particle identification, and relatively high energies will provide an excellent environment to search for new physics. If deviations from the standard three-flavor oscillation picture are seen however, it is crucial to know which new physics scenario is found so that it can be verified elsewhere and theoretically understood. We investigate several benchmark new physics scenarios by looking at existing long-baseline accelerator neutrino data from NOvA and T2K and determine at what sensitivity DUNE can differentiate among them. We consider sterile neutrinos and both vector and scalar non-standard neutrino interactions, all with new complex phases, the latter of which could conceivably provide absolute neutrino mass scale information. We find that, in many interesting cases, DUNE will have good model discrimination. We also perform a new fit to NOvA and T2K data with scalar NSI.

   hep-phJHEP(2023)·42 citations
4. 04*

   Mass decomposition of the pion in the 't Hooft model

   Adam Freese🇺🇸 · Gerald A. Miller🇺🇸

   We obtain the energy-momentum tensor (EMT) in the 't Hooft model of two-dimensional quantum chromodynamics. The EMT is decomposed into contributions from quark and gluon fields, with all of the (plus component of) the light front momentum being carried by the quark field. The energy is split between quark and gluon fields, with the gluon field carrying the self-energy of the dressed quarks. We consider the pion in the limit of small but non-zero quark masses -- which has previously withstood numerical treatment -- as as a concrete example. We solve for the pion wave function using a variational method and obtain numerical results for its energy breakdown into quark and gluon contributions.

   hep-phnucl-thPRD(2023)·4 citations
5. 05*

   Renormalization group effects for a rank degenerate Yukawa matrix and the fate of the massless neutrino

   Nicholas J. Benoit🇯🇵 · Takuya Morozumi🇯🇵 · Yusuke Shimizu🇯🇵 · Kenta Takagi🇯🇵 · Akihiro Yuu🇯🇵

   The Type-I seesaw model is a common extension to the Standard Model that describes neutrino masses. The Type-I seesaw introduces heavy right-handed neutrinos with Majorana mass that transform as Standard Model electroweak gauge singlets. We initially study a case with two right-handed neutrinos called the 3-2 model. At an energy scale above the right-handed neutrinos, the effective neutrino mass matrix is rank degenerate implying the lightest neutrino is massless. After considering renormalization effects below the two right-handed neutrinos, the effective neutrino mass matrix remains rank degenerate. Next, we study a model with three right-handed neutrinos called the 3-3 model. Above the energy scale of the three right-handed neutrinos, we construct the effective neutrino mass matrix to be rank degenerate. After solving for the renormalization effects to energies below the three right-handed neutrinos, we find the rank of the effective neutrino mass matrix depends on the kernel solutions of the renormalization group equations. We prove for the simplest kernel solutions the effective neutrino mass matrix remains rank degenerate.

   hep-phhep-exPTEP(2022)·2 citations
6. 06*

   Low-mass extension of direct detection bounds on WIMP-quark and WIMP-gluon effective interactions using the Migdal effect

   Gaurav Tomar🇩🇪 · Sunghyun Kang🇰🇷 · Stefano Scopel🇰🇷

   Updating a previous analysis where we used elastic nuclear recoils we study the Migdal effect to extend to low WIMP masses the direct detection bounds to operators up to dimension 7 of the relativistic effective field theory describing WIMP interactions with quarks and gluons. To this aim we include in our analysis the data of the XENON1T, SuperCDMS, COSINE-100, and DarkSide-50 experiments and assume a standard Maxwellian for the WIMP velocity distribution. We find that the bounds can reach down to a WIMP mass $\simeq$20 MeV, although in the case of higher-dimension operators the energy scale of the ensuing constraints may be inconsistent with the validity of the effective theory.

   hep-phhep-exAstropart.Phys.(2023)·17 citations
7. 07*

   SUSY-QCD corrections to squark annihilation into gluons and light quarks

   Luca Paolo Wiggering🇩🇪

   We calculate the full one-loop SUSY-QCD corrections to stop annihilation into gluons and light quarks including the Sommerfeld enhancement effect and discuss their impact on the neutralino relic density in the MSSM.

   hep-phSciPost Phys.Proc.(2023)·0 citations
8. 08*

   All possible first signals of gauge leptoquark in quark-lepton unification and beyond

   Hedvika Gedeonová🇨🇿 · Matěj Hudec🇨🇿

   We study possible current and future low-energy signals of the gauge leptoquark in quark-lepton SU(4) unification à la Pati-Salam. Taking fully into account the freedom in the generation mixing between quarks and leptons, we compile a catalogue of observables which currently form a border of the excluded part of the parameter space - hot candidates for first signals of new physics. We also determine the sensitivity needed in order to inspect a currently allowed part of the parameter space for several other measurements which are not included in this catalogue. We improve older similar works on this topic by taking into account more (and more recent) experimental measurements and by scanning the parameter space more densely. Furthermore, we study in a similar manner the SU(4) models with a small number of generations of extra leptons. We also discuss the minimal number of leptons needed in order to alleviate the contemporary discrepancies in the neutral-current B-meson decays.

   hep-phPRD(2023)·11 citations
9. 09*

   Higgs Boson Physics -- The View Ahead

   Howard E. Haber🇺🇸

   Eleven years ago, the Higgs boson was discovered at the LHC. I briefly survey the status of Higgs boson physics today and explore some of the implications for future Higgs studies. Although current experimental measurements are consistent with interpreting the observed Higgs boson as being consistent with the predictions of the Standard Model of particle physics, it is still possible that the Higgs boson is a member of an extended scalar sector that lies beyond the Standard Model. Nevertheless, an extended Higgs sector is already highly constrained. The Higgs sector can also serve as a portal to new physics beyond the Standard Model. Finally, two Higgs wishlists are assembled that merit future study and clarification at the LHC and future collider facilities now under development.

   hep-phLHEP(2023)·1 citation
10. 10*

    Far-from-equilibrium attractors for massive kinetic theory in the relaxation time approximation

    Huda Alalawi🇺🇸 · Michael Strickland🇺🇸

    We investigate whether early and late time attractors for non-conformal kinetic theories exist by computing the time-evolution of a large set of moments of the one-particle distribution function. For this purpose we make use of a previously obtained exact solution of the 0+1D boost-invariant massive Boltzmann equation in relaxation time approximation. We extend prior attractor studies of non-conformal systems by using a realistic mass- and temperature-dependent relaxation time and explicitly computing the effect of varying both the initial momentum-space anisotropy and initialization time on the time evolution of a large set of integral moments. Our findings are consistent with prior studies, which found that there is an attractor for the scaled longitudinal pressure, but not for the shear and bulk viscous corrections separately. We further present evidence that both late- and early-time attractors exist for all moments of the one-particle distribution function that contain greater than one power of the longitudinal momentum squared.

    hep-phnucl-thJHEP(2022)·18 citations
11. 11*

    Probing hidden spin-2 mediator of dark matter with NA64e, LDMX, NA64$\mu$ and M${}^3$

    I. V. Voronchikhin🇷🇺 · D. V. Kirpichnikov🇷🇺

    The connection between Standard Model (SM) particles and dark matter (DM) can be introduced via hidden spin-2 massive mediator. In the present paper we consider the simplified benchmark link between charged lepton sector of SM and DM particles which are considered to be a hidden Dirac fermions from the dark sector. The regarding couplings are established through the dimension-5 operators involving spin-2 mediator field and the energy-momentum tensors of both SM and DM sectors. We study in detail the implication of this scenario for the lepton fixed-target facilities, such as NA64$e$, LDMX, NA64$\mu$ and M${}^3$. In particular, for the specific experiment we discuss in detail the missing-energy signatures of spin-2 boson production followed by its invisible decay into stable DM pairs. Moreover, we derive the expected reaches of these experiments for the projected statistics of the leptons accumulated on the target. We also discuss the implication of both nuclear and atomic form-factor parametrizations for the differential spectra of hidden spin-$2$ boson emission, the total cross-section of its production and the experimental reach of the fixed-fixed target facilities for probing hidden spin-$2$ DM mediator.

    hep-phPRD(2022)·12 citations
12. 12*

    Anomalous enhancement of dilepton production due to soft modes in dense quark matter

    Toru Nishimura🇯🇵 · Masakiyo Kitazawa🇯🇵 · Teiji Kunihiro🇯🇵

    We explore how the dilepton production rate is modified near the critical temperature of color superconductivity and QCD critical point by the soft modes inherently associated with the phase transitions of second-order. It is shown that the soft modes affect the photon self-energy significantly through so called the Aslamasov-Larkin, Maki-Thompson and density of states terms, which are known responsible for the paraconductivity in the metalic superconductivity, and cause an anomalous enhancement of the production rate in the low energy/momentum region.

    hep-phEPJ Web Conf.(2023)·0 citations
13. 13*

    $X(3860)$ production in association with $J/\psi$ via $e^{+}{e}^{-}$ annihilation at Belle

    Gui-Yuan Zhang🇨🇳 · Cong Li🇨🇳 · Ying-Zhao Jiang🇨🇳 · Zhan Sun🇨🇳

    In this paper, we study the $X(3860)$ production associated with $J/\psi$ via $e^{+}{e}^{-}$ annihilation at the next-to-leading-order (NLO) QCD accuracy, within the nonrelativistic QCD (NRQCD) framework. Under the hypothesis of $J_{X(3860)}^{PC}=0^{++}$, the predicted total cross sections agree well with the Belle's measurements at $\sqrt{s}={\rm Y}(4S,5S)$, while the theoretical results given by the $2^{++}$ hypothesis significantly undershoot the data. This is consistent with the Belle's conclusion that the $0^{++}$ hypothesis is favored over the $2^{++}$ hypothesis for $X(3860)$. Despite the agreement of the total cross sections, the NRQCD predictions seem to be incompatible with the Belle-measured $J/\psi$ angular distributions. We also perform the NLO calculations of ${\sigma }_{e^{+}{e}^{-}\to J/\psi +X(3940)}$ on the assumption of $J_{X(3940)}^{PC}=0^{-+}$, discovering that the NRQCD predictions that coincide with the light-cone results are in good agreement with the experiment.

    hep-phEPJC(2023)·0 citations
14. 14*

    Fitting a Self-Interacting Dark Matter Model to Data Ranging From Satellite Galaxies to Galaxy Clusters

    Sudhakantha Girmohanta🇺🇸 · Robert Shrock🇺🇸

    We present a fit to observational data in an asymmetric self-interacting dark matter model using our recently calculated cross sections that incorporate both $t$-channel and $u$-channel exchanges in the scattering of identical particles. We find good fits to the data ranging from dwarf galaxies to galaxy clusters, and equivalent relative velocities from $\sim 20$ km/sec to $\gtrsim 10^3$ km/s. We compare our results with previous fits that used only $t$-channel exchange contributions to the scattering.

    hep-phastro-ph.COastro-ph.GAhep-ex+1PRD(2023)·11 citations
15. 15*

    The Stochastic Relaxion

    Aleksandr Chatrchyan🇩🇪 · Géraldine Servant🇩🇪

    We revisit the original proposal of cosmological relaxation of the electroweak scale by Graham, Kaplan and Rajendran in which the Higgs mass is scanned during inflation by an axion field, the relaxion. We investigate the regime where the relaxion is subject to large fluctuations during inflation. The stochastic dynamics of the relaxion is described by means of the Fokker-Planck formalism. We derive a new stopping condition for the relaxion taking into account transitions between the neighboring local minima of its potential. Relaxion fluctuations have important consequences even in the "classical-beats-quantum" regime. We determine that for a large Hubble parameter during inflation, the random walk prevents the relaxion from getting trapped at the first minimum. The relaxion stops much further away, where the potential is less shallow. Interestingly, this essentially jeopardises the "runaway relaxion" threat from finite-density effects, restoring most of the relaxion parameter space. We also explore the "quantum-beats-classical" regime, opening large new regions of parameter space. We investigate the consequences for both the QCD and the non-QCD relaxion. The misalignment of the relaxion due to fluctuations around its local minimum opens new phenomenological opportunities.

    hep-phastro-ph.COJHEP(2023)·16 citations
16. 16*

    The Higgs condensate as a quantum liquid: A critical comparison with observations

    Paolo Cea🇮🇹

    The triviality of four-dimensional scalar quantum field theories poses challenging problems to the usually adopted perturbative implementation of the Higgs mechanism. In the first part of the paper we compare the triviality scenario and the renormalised two-loop perturbation theory to precise and extensive results from non-perturbative numerical simulations of the real scalar field theory on the lattice. The proposal of triviality and spontaneous symmetry breaking turns out to be in good agreement with numerical simulations, while the renormalised perturbative approach seems to suffer significant deviations from the numerical simulation results. In the second part of the paper we try to illustrate how the triviality of four-dimensional scalar field theory leads, nevertheless, to the spontaneous symmetry breaking in the scalar sector of the Standard Model. We show how triviality allows us to develop a physical picture of the Higgs mechanism in the Standard Model. We suggest that the Higgs condensate behave like a relativistic quantum liquid leading to the prevision of two Higgs bosons. The light Higgs boson resembles closely the new LHC narrow resonance at 125 GeV. The heavy Higgs boson is a rather broad resonance with mass of about 730 GeV. We critically compare our proposal to the complete LHC Run 2 data collected by the ATLAS and CMS Collaborations. We do not find convincingly evidences of the heavy Higgs boson in the ATLAS datasets. On the other hand, the CMS full Run 2 data display evidences of a heavy Higgs boson in the main decay modes $H\to WW$, while in the preliminary Run 2 data there are hints of the decays $H\to ZZ$ in the golden channel. We also critically discuss plausible reasons for the discrepancies between the two LHC experiments.

    hep-phhep-exhep-latInt.J.Mod.Phys.A(2023)·3 citations
17. 17*

    The role of the underlying event in the charm-baryon enhancement observed in pp collisions at LHC energies

    Zoltán Varga🇭🇺 · Anett Misák🇭🇺 · Róbert Vértesi🇭🇺

    We study the enhanced production of ${\Lambda }_c$ charmed baryons relative to that of charmed $D^0$ mesons in proton-proton collisions at LHC energies. We simulated collision events with the enhanced color-reconnection model in PYTHIA 8 MC generator and propose measurements based on the comparative use of different event-activity classifiers to identify the source of the charmed-baryon enhancement. We demonstrate that in this enhanced color-reconnection scenario the excess production is primarily linked to the underlying event and not to the production of high-momentum jets.

    hep-phSciPost Phys.Proc.(2024)·1 citation
18. 18*

    Infrared Divergence and Low Energy Theorem in Non-Abelian Gauge Theory

    Akio Sugamoto🇯🇵

    In the thesis, first, the cancellation of infrared divergences in QED is reviewed. Next, two examples in QCD, the quark-quark scattering and the quark-gluon scattering are examined at one loop, from which the importance of Ward-Takahashi identities becomes manifest for the cancellation to occur. The factorization of infrared divergences in QCD is proved at all orders, by full usage of the Ward-Takahashi identities. In these proofs, the axial gauge condition is used. The cancellation of infrared divergences in QCD occurs among the gauge invariant set of graphs. In this way, the low energy theorem of F. E. Low, for emission of one or two soft gluons, are proved at all orders. From this, the differential equation controlling the infrared divergences in QCD is derived. In QCD, the coupling constant renormalization introduces the other infrared divergence, which is governed by the beta-function in the pure Yang-Mills theory. In the Epilogue 2022, a motivation for recently translating the thesis in English is briefly stated.

    hep-phhep-th0 citations
19. 19*

    India Based Neutrino Observatory, Physics Reach and Status Report

    D. Indumathi🇮🇳

    The India-based Neutrino Observatory (INO) is a proposed underground facility located in India that will primarily house the magnetised Iron CALorimeter (ICAL) detector to study atmospheric neutrinos produced by interactions of cosmic rays with Earth's atmosphere. The physics goal is to to make precision measurements of the neutrino mixing and oscillation parameters through such a study. We present here the results from detailed simulations studies, as well as a status report on the project. In particular, we highlight the sensitivity of ICAL to the open issue of the neutrino mass ordering, which can be determined {\it independent of the CP phase} at ICAL.

    ↳ hep-exhep-phSciPost Phys.Proc.(2023)·0 citations
20. 20*

    Newton versus Coulomb for Kaluza-Klein modes

    Karim Benakli🇫🇷 · Carlo Branchina🇫🇷 · Gaëtan Lafforgue-Marmet🇫🇷

    We consider a set of elementary compactifications of $D+1$ to $D$ spacetime dimensions on a circle: first for pure general relativity, then in the presence of a scalar field, first free then with a non minimal coupling to the Ricci scalar, and finally in the presence of gauge bosons. We compute the tree-level amplitudes in order to compare some gravitational and non-gravitational amplitudes. This allows us to recover the known constraints of the $U(1)$, dilatonic and scalar Weak Gravity Conjectures in some cases, and to show the interplay of the different interactions. We study the KK modes pair-production in different dimensions. We also discuss the contribution to some of these amplitudes of the non-minimal coupling in higher dimensions for scalar fields to the Ricci scalar.

    ↳ hep-thgr-qchep-phEPJC(2023)·12 citations
21. 21*

    Short-range forces due to Lorentz-symmetry violation

    Quentin G. Bailey🇺🇸 · Jennifer L. James🇺🇸 · Janessa R. Slone🇺🇸 · Kellie O'Neal-Ault🇺🇸

    Complementing previous theoretical and experimental work, we explore new types of short-range modifications to Newtonian gravity arising from spacetime-symmetry breaking. The first non-perturbative, i.e., to all orders in coefficients for Lorentz-symmetry breaking, are constructed in the Newtonian limit. We make use of the generic symmetry-breaking terms modifying the gravity sector and examine the isotropic coefficient limit. The results show new kinds of force law corrections, going beyond the standard Yukawa parameterization. Further, there are ranges of the values of the coefficients that could make the resulting forces large compared to the Newtonian prediction at short distances. Experimental signals are discussed for typical test mass arrangements.

    ↳ gr-qchep-phhep-thClass.Quant.Grav.(2023)·8 citations
22. 22*

    Probing the valence quark region of nucleons with Z bosons at LHCb

    Tianqi Li🇨🇳

    Because of its forward coverage, LHCb can probe the valence quark distributions of protons and nuclei at small and large Bjorken-x with high precision. This proceeding presents new LHCb measurements of Z boson production in association with charm jet in the forward region of proton-proton collisions and Z boson production in proton-lead collisions. Z+charm jet production could be sensitive to a valence-like intrinsic-charm component in the proton wave function. The measurements of Z production in proton-lead collisions provide new constraints on the partonic structure of nucleons inside nuclei. Comparisons between the results and calculations with parton distribution functions are also discussed.

    ↳ hep-exhep-phActa Phys.Polon.Supp.(2023)·0 citations
23. 23*

    Galaxy clusters in high definition: a dark matter search

    Geoff Beck🇿🇦 · Michael Sarkis🇿🇦

    Recent radio-frequency probes, with the ATCA and ASKAP telescopes, have proven themselves to be at the forefront of placing indirect limits on the properties of dark matter. The latter being able to substantially exceed the constraining power of Fermi-LAT data. However, these observations were based only on dwarf galaxies, where magnetic field uncertainties are large. Here we re-examine the case for galaxy clusters, often ignored due to substantial diffuse radio backgrounds, by considering the extrapolation of known cluster surface brightness profiles down to scales observable with MeerKAT. Despite large baryonic backgrounds, we find that clusters can be competitive with dwarf galaxies. Extrapolated Coma data being able to rule out WIMPs of mass $<700$ GeV annihilating via $b$-quarks. This is while having lesser uncertainties surrounding the magnetic field and diffusive environment. Such compelling results are possible due to a clash between the inner shape of the dark matter halo and the flat inner profile of radio halos which is most pronounced for NFW-like Einasto profiles, the presence of which having some supporting evidence in the literature.

    ↳ astro-ph.COhep-phPRD(2023)·10 citations
24. 24*

    Massive gravitino scattering amplitudes and the unitarity cutoff of the new Fayet-Iliopoulos terms

    Ignatios Antoniadis🇫🇷 · Anthony Guillen🇫🇷 · François Rondeau🇫🇷

    We compute the $2\to 2$ gravitino scattering amplitudes at tree level in supergravity theories where supersymmetry is spontaneously broken. In the unitary gauge, the gravitino becomes massive (of mass $m_{3/2}$) by absorbing the Goldstino, and the scattering amplitudes of its longitudinal polarisations grow with energy as ${\kappa }^2{E}^4/m_{3/2}^2$, signaling a potential breakdown of unitarity at a scale ${\Lambda }^2\sim m_{3/2}/\kappa \sim M_{\mathrm{SUSY}}^2$. As we show explicitly in the Polonyi model, this leading term is cancelled by the contributions coming from the scalar partner of the Goldstino (sgoldstino), restoring perturbative unitarity up to the Planck scale. This is expected since supersymmetry is spontaneously broken, in analogy with the situation occuring in the Standard Model, where massive gauge bosons scattering preserves unitarity at high energy once we consider the contributions from the Higgs boson. However, when supersymmetry is broken by the new Fayet-Iliopoulos $D$-term, with ungauged R-symmetry, the above cancellation does not occur. In this case, the unbroken phase is singular and there is no contribution able to cancel the quartic divergences of the amplitudes, leading to a cutoff $\Lambda \sim M_{\mathrm{SUSY}}$ where the effective theory breaks down. The same behaviour is obtained when supersymmetry is non-linearly realised.

    ↳ hep-thgr-qchep-phJHEP(2023)·10 citations
25. 25*

    Fissile isotopes antineutrino spectra: summation method and direct experiment

    P. Naumov🇷🇺 · S. Silaeva🇷🇺 · V. Sinev🇷🇺 · A. Vlasenko🇷🇺

    New antineutrino spectra of fissile isotopes (${}^{235}$U, ${}^{238}$U, ${}^{239}$Pu and ${}^{241}$Pu) which are containing in a nuclear reactor fuel have been obtained. A combined technique was used: calculation of antineutrino spectra and their fitting to those obtained in the experiment at the Rovno NPP in the 80s of the last century. The cross sections of fissile isotopes calculated with these spectra describe well the cross section obtained experimentally in the Double Chooz experiment. The calculated cross section for the same reactor core composition is ${\sigma }_f=(5.82\pm 0.12)\times 10^{-43}$ cm${}^2$/fission. It is the closest result between all predicted. The obtained spectra have the same "bump" as experimental ones in 5 MeV observed energy region.

    ↳ nucl-exhep-ph0 citations
26. 26*

    Issues in Palatini ${\mathcal{R}}^2$ inflation: Bounds on the Reheating Temperature

    A. B. Lahanas🇬🇷

    We consider ${\mathcal{R}}^2$-inflation in Palatini gravity, in the presence of scalar fields coupled to gravity. These theories, in the Einstein frame, and for one scalar field $h$, share common features with $K$ - inflation models. We apply this formalism for the study of single-field inflationary models, whose potentials are monomials, $V\sim h^n$, with $n$ a positive even integer. We also study the Higgs model non-minimally coupled to gravity. With ${\mathcal{R}}^2$-terms coupled to gravity as $\sim \alpha {\mathcal{R}}^2$, with $\alpha$ constant, the instantaneous reheating temperature $T_{ins}$, is bounded by $T_{ins}\le 0.290m_{Planck}/{\alpha }^{1/4}$, with the upper bound being saturated for large $\alpha$. For such large $\alpha$ need go beyond slow-roll to calculate reliably the cosmological parameters, among these the end of inflation through which $T_{ins}$ is determined. In fact, as inflaton rolls towards the end of inflation point, the quartic in the velocity terms, unavoidable in Palatini gravity, play a significant role and can not be ignored. The values of $\alpha$, and other parameters, are constrained by cosmological data, setting bounds on the inflationary scale $M_s\sim 1/\sqrt{\alpha }$ and the reheating temperature of the Universe.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2022)·12 citations
27. 27*

    Schwinger-Keldysh path integral formalism for a Quenched Quantum Inverted Oscillator

    Sayantan Choudhury🇮🇳 · Suman Dey🇮🇳 · Rakshit Mandish Gharat🇮🇳 · Saptarshi Mandal🇮🇳 · Nilesh Pandey🇮🇳

    In this work, we study the time-dependent behaviour of quantum correlations of a system of an inverted oscillator governed by out-of-equilibrium dynamics using the well-known Schwinger-Keldysh formalism in presence of quantum mechanical quench. Considering a generalized structure of a time-dependent Hamiltonian for an inverted oscillator system, we use the invariant operator method to obtain its eigenstates and continuous energy eigenvalues. Using the expression for the eigenstates, we further derive the most general expression for the generating function as well as the out-of-time-ordered correlators (OTOC) for the given system using this formalism. Further, considering the time-dependent coupling and frequency of the quantum inverted oscillator characterized by quench parameters, we comment on the dynamical behaviour, specifically the early, intermediate and late time-dependent features of the OTOC for the quenched quantum inverted oscillator. Next, we study a specific case, where the system of inverted oscillator exhibits chaotic behaviour by computing the quantum Lyapunov exponent from the time-dependent behaviour of OTOC in presence of the given quench profile.

    ↳ hep-thcond-mat.stat-mechgr-qchep-ph+1Symmetry(2024)·2 citations
28. 28*

    Thermodynamic solution of the homogeneity, isotropy and flatness puzzles (and a clue to the cosmological constant)

    Latham Boyle🇨🇦 · Neil Turok🇨🇦

    We obtain the analytic solution of the Friedmann equation for fully realistic cosmologies including radiation, non-relativistic matter, a cosmological constant $\lambda$ and arbitrary spatial curvature $\kappa$. The general solution for the scale factor $a(\tau )$, with $\tau$ the conformal time, is an elliptic function, meromorphic and doubly periodic in the complex $\tau$-plane, with one period along the real $\tau$-axis, and the other along the imaginary $\tau$-axis. The periodicity in imaginary time allows us to compute the thermodynamic temperature and entropy of such spacetimes, just as Gibbons and Hawking did for black holes and the de Sitter universe. The gravitational entropy favors universes like our own which are spatially flat, homogeneous, and isotropic, with a small positive cosmological constant.

    ↳ gr-qcastro-ph.COhep-phhep-thPLB(2024)·21 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.