Fri·Mar 5, 2021Friday·March 5, 2021

1. 01*

   Twin Modular $S_4$ with $SU(5)$ GUT

   Stephen F. King🇬🇧 · Ye-Ling Zhou🇬🇧

   We discuss the $SU(5)$ grand unified extension of flavour models with multiple modular symmetries. The proposed model involves two modular $S_4$ groups, one acting in the charged fermion sector, associated with a modulus field value ${\tau }_T$ with residual $Z_3^T$ symmetry, and one acting in the right-handed neutrino sector, associated with another modulus field value ${\tau }_{SU}$ with residual $Z_2^{SU}$ symmetry. Quark and lepton mass hierarchies are naturally generated with the help of weightons, which are SM singlet fields, where their non-zero modular weights play the role of Froggatt-Nielsen charges. The model predicts TM${}_1$ lepton mixing, and neutrinoless double beta decay at rates close to the sensitivity of current and future experiments, for both normal and inverted orderings, with suppressed corrections from charged lepton mixing due to the triangular form of its Yukawa matrix.

   hep-phJHEP(2021)·60 citations
2. 02*

   What is matter according to particle physics and why try to observe its creation in lab

   Francesco Vissani🇮🇹

   The standard model of elementary interactions has long qualified as a theory of matter, in which the postulated conservation laws (one baryonic and three leptonic) acquire theoretical meaning. However, recent observations of lepton number violations -- neutrino oscillations -- demonstrate its incompleteness. We discuss why these considerations suggest the correctness of Ettore Majorana's ideas on the nature of neutrino mass, and add further interest to the search for an ultra-rare nuclear process in which two particles of matter (electrons) are created, commonly called neutrinoless double beta decay. The approach of the discussion is mainly historical and its character is introductory. Some technical considerations, which highlight the usefulness of Majorana's representation of gamma matrices, are presented in the appendix.

   hep-phastro-ph.HEhep-thUniverse(2021)·10 citations
3. 03*

   Dynamical inverse seesaw mechanism as a simple benchmark for electroweak breaking and Higgs boson studies

   Sanjoy Mandal🇪🇸 · Jorge C. Romão🇵🇹 · Rahul Srivastava🇮🇳 · José W. F. Valle🇪🇸

   The Standard Model(SM) vacuum is unstable for the measured values of the top Yukawa coupling and Higgs mass. Here we study the issue of vacuum stability when neutrino masses are generated through spontaneous low-scale lepton number violation. In the simplest dynamical inverse seesaw, the SM Higgs has two siblings: a massive CP-even scalar plus a massless Nambu-Goldstone boson, called majoron. For TeV scale breaking of lepton number, Higgs bosons can have a sizeable decay into the invisible majorons. We examine the interplay and complementarity of vacuum stability and perturbativity restrictions, with collider constraints on visible and invisible Higgs boson decay channels. This simple framework may help guiding further studies, for example, at the proposed FCC facility.

   hep-phJHEP(2021)·15 citations
4. 04*

   Estimating the impact of mixed QCD-electroweak corrections on the $W$-mass determination at the LHC

   Arnd Behring🇩🇪 · Federico Buccioni🇬🇧 · Fabrizio Caola🇬🇧 · Maximilian Delto🇩🇪 · Matthieu Jaquier🇩🇪 · Kirill Melnikov🇩🇪 · Raoul Röntsch🇨🇭

   We study the impact of the recently computed mixed QCD-electroweak corrections to the production of $W$ and $Z$ bosons at the LHC on the value of the $W$ mass extracted from the transverse momentum distribution of charged leptons from $W$ decays. Using the average lepton transverse momenta in $W$ and $Z$ decays as simplified observables for the determination of the $W$ mass, we estimate that mixed QCD-electroweak corrections can shift the extracted value of the $W$ mass by up to $\mathcal{O}(20)\mathrm{MeV}$, depending on the kinematic cuts employed to define fiducial cross sections for $Z$ and $W$ production. Since the target precision of the $W$-mass measurement at the LHC is $\mathcal{O}(10)\mathrm{MeV}$, our results emphasize the need for fully-differential computations of mixed QCD-electroweak corrections and a careful analysis of their potential impact on the determination of the $W$ mass.

   hep-phPRD(2021)·26 citations
5. 05*

   $W^{+}{W}^{-}H$ production through bottom quarks fusion at hadron colliders

   Pankaj Agrawal🇮🇳 · Biswajit Das🇮🇳

   With the standard model working well in describing the collider data, the focus is now on determining the standard model parameters as well as for any hint of deviation. In particular, the determination of the couplings of the Higgs boson with itself and with other particles of the model is important to better understand the electroweak symmetry breaking sector of the model. In this letter, we look at the process $pp\to WWH$, in particular through the fusion of bottom quarks. Due to the non-negligible coupling of the Higgs boson with the bottom quarks, there is a dependence on the $WWHH$ coupling in this process. This sub-process receives largest contribution when the $W$ bosons are longitudinally polarized. We compute one-loop QCD corrections to various final states with polarized $W$ bosons. We find that the corrections to the final state with the longitudinally polarized $W$ bosons are large. It is shown that the measurement of the polarization of the $W$ bosons can be used as a tool to probe the $WWHH$ coupling in this process. We also examine the effect of varying $WWHH$ coupling in the $\kappa$-framework.

   hep-phhep-exPLB(2021)·4 citations
6. 06*

   Radion dynamics, heavy Kaluza-Klein resonances and gravitational waves

   Eugenio Megias🇪🇸 · Germano Nardini🇳🇴 · Mariano Quiros🇪🇸

   We study the confinement/deconfinement phase transition of the radion field in a warped model with a polynomial bulk potential. The backreaction of the radion on the metric is taken into account by using the superpotential formalism, while the radion effective potential is obtained from a novel formulation which can incorporate the backreaction. The phase transition leads to a stochastic gravitational wave background that depends on the energy scale of the first Kaluza-Klein resonance, $m_{\text{KK}}$. This work completes previous studies in the following aspects: i) we detail the evaluation of the radion spectrum; ii) we report on the mismatches between the thick wall approximation and the numerical bounce solution; iii) we include a suppression factor in the spectrum of sound waves accounting for their finite lifetime; and, iv) we update the bound on $m_{\text{KK}}$ in view of the O3 LIGO and Virgo data. We find that the forthcoming gravitational wave interferometers can probe scenarios where $m_{\text{KK}}\lesssim 10^9$ TeV, while the O3-run bounds rule out warped models with $10^4\text{TeV}\lesssim m_{\text{KK}}\lesssim 10^7$ TeV exhibiting an extremely strong confinement/deconfinement phase transition.

   hep-phgr-qchep-thInt.J.Mod.Phys.A(2022)·3 citations
7. 07*

   Axion mass in antiferromagnetic insulators

   Koji Ishiwata🇯🇵

   We calculate axion potential in antiferromagnetic insulators from path integral. It is derived from the effective potential for the order parameter of the antiferromagnetic phase in insulators. Static and dynamical axions are defined consistently from the potential. Consequently antiferromagnetic/paramagnetic and topological/normal orders are classified. The dynamical axion is predicted in all phases and its mass turns out to be various values up to eV scale.

   hep-phcond-mat.mes-hallcond-mat.str-elPRD(2021)·7 citations
8. 08*

   Exclusive rare Higgs decays into lepton pair and light mesons

   Dao-Neng Gao🇨🇳 · Xi Gong🇨🇳

   Exclusive rare Higgs decays into lepton pair plus one light hadron, such as $h\to {\rho }^0(\omega )\ell \bar{\ell }$, $h\to {\pi }^0\ell \bar{\ell }$, $h\to {\pi }^{+}(K^{+}){\ell }^{-}{\bar{\nu }}_{\ell }$, and $h\to {\rho }^{+}(K^{\ast +}){\ell }^{-}{\bar{\nu }}_{\ell }$, have been explored in the standard model. Decay amplitudes are dominantly from the Higgs couplings to gauge bosons and to charged leptons, and their branching ratios are predicted in the range of $10^{-8}\sim 10^{-5}$. We have also analyzed the differential dilepton invariant mass and angular distributions of $h\to {\rho }^0{\ell }^{+}{\ell }^{-}$ decays. It will be challenging to search for these rare processes. Nevertheless, experimental studies of them, in particular, $h\to {\rho }^0{\ell }^{+}{\ell }^{-}$ with $\ell =e,\mu$, might be interesting both to help deepen our understanding of the standard model and to probe new physics beyond the standard model in the future high-precision experiments.

   hep-phhep-exPLB(2021)·2 citations
9. 09*

   Newly observed $X(4630)$: a new charmoniumlike molecule

   Xin-Dian Yang🇨🇳 · Fu-Lai Wang🇨🇳 · Zhan-Wei Liu🇨🇳 · Xiang Liu🇨🇳

   Very recently, the LHCb Collaboration at the Large Hadron Collider at CERN observed new resonance $X(4630)$. The $X(4630)$ is decoded as a charmoniumlike molecule with hidden-strange quantum number well in the one boson exchange mechanism. Especially, the study of its hidden-charmed decays explicitly shows the dominant role of $J/\psi \varphi$ among all allowed hidden-charmed decays of $X(4630)$, which enforces the conclusion of $X(4630)$ as a charmoniumlike molecule. The discovery of the $X(4630)$ is a crucial step of constructing charmoniumlike molecule zoo.

   hep-phEPJC(2021)·29 citations
10. 10*

    Detecting anomalous quartic gauge couplings using the isolation forest machine learning algorithm

    Li Jiang🇨🇳 · Yu-Chen Guo🇨🇳 · Ji-Chong Yang🇨🇳

    The search of new physics~(NP) beyond the Standard Model is one of the most important tasks of high energy physics. A common characteristic of the NP signals is that they are usually few and kinematically different. We use a model independent strategy to study the phenomenology of NP by directly picking out and studying the kinematically unusual events. For this purpose, the isolation forest~(IF) algorithm is applied, which is found to be efficient in identifying the signal events of the anomalous quartic gauge couplings~(aQGCs). The IF algorithm can also be used to constraint the coefficients of aQGCs. As a machine learning algorithm, the IF algorithm shows a good prospect in the future studies of NP.

    hep-phPRD(2021)·16 citations
11. 11*

    Prediction of mass of ${\eta }_c$ (2S) using variational method

    Chandrashekar Radhakrishnan🇫🇷

    The suitability of using non-relativistic quantum mechanics to investigate heavy quark mesons is illustrated through a study of the charmonium meson. We consider a limiting form of the QCD potential which is a simple combination of the linear and Coulomb potential. The experimentally determined masses of $J/\psi (1S)$ and ${\chi }_{c1}(1P)$ are reproduced for $m_c\approx 1.1GeV$. For $\psi (2S)$ we have three different sets of variational parameters and to choose the appropriate one we use the leptonic decay width of $\psi (2S)$ and $J/\psi (1S)$. Finally we use a spin-spin interaction to investigate the hyperfine splitting of Charmonium and use it to calculate the mass of ${\eta }_c(2S)$. Our theoretical results agree with the experimentally measured values of ${\eta }_c(2S)$ and thereby verifies the usefulness of non-relativistic quantum mechanics in the study of heavy quark meson.

    hep-ph0 citations
12. 12*

    Nucleon mass radii and distribution: Holographic QCD, Lattice QCD and GlueX data

    Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸

    We briefly review and expand our recent analysis for all three invariant A,B,D gravitational form factors of the nucleon in holographic QCD. They compare well to the gluonic gravitational form factors recently measured using lattice QCD simulations. The holographic A-term is fixed by the tensor $T=2^{++}$ (graviton) Regge trajectory, and the D-term by the difference between the tensor $T=2^{++}$ (graviton) and scalar $S=0^{++}$ (dilaton) Regge trajectories. The B-term is null in the absence of a tensor coupling to a Dirac fermion in bulk. A first measurement of the tensor form factor A-term is already accessible using the current GlueX data, and therefore the tensor gluonic mass radius, pressure and shear inside the proton, thanks to holography. The holographic A-term and D-term can be expressed exactly in terms of harmonic numbers. The tensor mass radius from the holographic threshold is found to be $⟨r_{GT}^2⟩\approx (0.57-0.60\mathrm{fm}{)}^2$, in agreement with $⟨r_{GT}^2⟩\approx (0.62\mathrm{fm}{)}^2$ as extracted from the overall numerical lattice data, and empirical GlueX data. The scalar mass radius is found to be slightly larger $⟨r_{GS}^2⟩\approx (0.7\mathrm{fm}{)}^2$.

    hep-phhep-latnucl-exnucl-thPRD(2021)·85 citations
13. 13*

    The Hubble Tension as a Hint of Leptogenesis and Neutrino Mass Generation

    Miguel Escudero🇩🇪 · Samuel J. Witte🇳🇱

    The majoron, a neutrinophilic pseudo-Goldstone boson conventionally arising in the context of neutrino mass models, can damp neutrino free-streaming and inject additional energy density into neutrinos prior to recombination. The combination of these effects for an eV-scale mass majoron has been shown to ameliorate the outstanding $H_0$ tension, however only if one introduces additional dark radiation at the level of $\Delta N_{\mathrm{eff}}\sim 0.5$. We show here that models of low-scale leptogenesis can naturally source this dark radiation by generating a primordial population of majorons from the decays of GeV-scale sterile neutrinos in the early Universe. Using a posterior predictive distribution conditioned on Planck2018+BAO data, we show that the value of $H_0$ observed by the SH${}_0$ES collaboration is expected to occur at the level of $\sim 10\%$ in the primordial majoron cosmology (to be compared with $\sim 0.1\%$ in the case of $\Lambda$CDM). This insight provides an intriguing connection between the neutrino mass mechanism, the baryon asymmetry of the Universe, and the discrepant measurements of $H_0$.

    hep-phastro-ph.COEPJC(2021)·96 citations
14. 14*

    Freeze-In Dark Matter within the Seesaw mechanism

    Michele Lucente🇩🇪

    We show that the minimal Type-I Seesaw mechanism can successfully account for the observed dark matter abundance in the form of a keV sterile neutrino. This population can be produced by the decay of the heavier neutral leptons, with masses above the Higgs mass scale, while they are in thermal equilibrium in the early Universe (freeze-in). Moreover, the implementation of the relevant phenomenological constraints (relic abundance, indirect detection and structure formation) on this model automatically selects a region of the parameter space featuring an approximate lepton number symmetry.

    hep-phastro-ph.COPLB(2023)·12 citations
15. 15*

    Heavy decaying dark matter at future neutrino radio telescopes

    Marco Chianese🇮🇹 · Damiano F.G. Fiorillo🇮🇹 · Rasmi Hajjar🇮🇹 · Gennaro Miele🇮🇹 · Stefano Morisi🇮🇹 · Ninetta Saviano🇮🇹

    In the next decades, ultra-high-energy neutrinos in the EeV energy range will be potentially detected by next-generation neutrino telescopes. Although their primary goals are to observe cosmogenic neutrinos and to gain insight into extreme astrophysical environments, they can also indirectly probe the nature of dark matter. In this paper, we study the projected sensitivity of up-coming neutrino radio telescopes, such as RNO-G, GRAND and IceCube-gen2 radio array, to decaying dark matter scenarios. We investigate different dark matter decaying channels and masses, from $10^7$ to $10^{15}$ GeV. By assuming the observation of cosmogenic or newborn pulsar neutrinos, we forecast conservative constraints on the lifetime of heavy dark matter particles. We find that these limits are competitive with and highly complementary to previous multi-messenger analyses.

    hep-phastro-ph.COJCAP(2021)·39 citations
16. 16*

    Bayesian probability for leptonic CP phase with strong CP prior

    Ravi Kuchimanchi

    In a world devoid of axions, the smallness of the strong CP phase can have implications for leptonic CP violation being probed by neutrino experiments. For example, if nature adopted an axionless solution to the strong CP problem, the same symmetries that set the strong CP phase to zero at the tree-level, may also set the leptonic $CP$ phases to zero (mod \pi). This automatically happens in the left-right symmetric model when it is extended minimally to solve the strong CP problem by imposition of both P and CP. In the Nelson Barr solution the needed symmetries can be assigned so that leptonic CP violation is not generated. In the minimal left-right symmetric model with P (and not CP), where the strong CP problem remains, leptonic CP phases radiatively generate the strong CP phase in one loop, and therefore they may be absent (negligibly small) in large regions of parameter space. All these results motivate us to consider a Bayesian prior for leptonic Dirac CP phase \delta_{CP} of the PMNS matrix that has delta function like peaks at CP conserving values of 0 and \pi on top of a uniform distribution. We evaluate the posterior probability distribution for \delta_{CP} using the current global fit to neutrino experiments and find significant enhancements for the probability that \delta_{CP} is at or negligibly close to \pi. We also provide useful tables for the posterior probability considering present and future experimental sensitivities.

    hep-phhep-ex0 citations
17. 17*

    Application of the triangulated category to the explanation of fully-charm tetraquark mass

    T.V. Obikhod🇺🇦

    The discovery in July 2020 of fully-charm tetraquark led to the need for its theoretical explanation. For investigation of such complex four-quark formation, the modern mathematical apparatus of the theory of derived categories is used. By representing diquarks as solitonic objects in terms of sheaves, one can explain the measured mass of the broad resonance of fully-charm tetraquarks consisting of di-charmonia.

    hep-phInterConf, 2021 (42), 934-939·2 citations
18. 18*

    Sorkin parameter for type-I spontaneous parametric down-conversion biphotons and matter waves

    F. C. V. de Brito🇧🇷 · C. H. S. Vieira🇧🇷 · I. G. da Paz🇧🇷 · J. B. Araujo🇧🇷 · M. Sampaio🇧🇷

    We propose experimental measurements of the logarithmic negativity, which quantifies quantum correlations using Gouy phase measurements in an asymmetric double-slit interference experiment for twin photons. This is possible because both quantities have analogous dependence with the spatial confinement by the slits and enables one to manipulate the portion of entanglement by the Gouy phase. In order to obtain those measurements, we need to work in a regime where the position correlations between particles are strong, therefore we investigate such correlations for biphotons. Since we would like to handle entanglement quantifiers through the Gouy phase, we analyze the Gouy phase difference for two entangled photons in an asymmetric double-slit interference experiment.

    ↳ quant-phhep-phphysics.opticsPRA(2021)·2 citations
19. 19*

    Low-Energy String Theory Predicts Black Holes Hide a New Universe

    Robert Brandenberger🇨🇦 · Lavinia Heisenberg🇨🇭 · Jakob Robnik🇨🇭

    We propose a construction with which to resolve the black hole singularity and enable an anisotropic cosmology to emerge from the inside of the hole. The model relies on the addition of an S-brane to the effective action which describes the geometry of space-time. This space-like defect is located inside of the horizon on a surface where the Weyl curvature reaches a limiting value. We study how metric fluctuations evolve from the outside of the black hole to the beginning of the cosmological phase to the future of the S-brane. Our setup addresses i) the black hole singularity problem, ii) the cosmological singularity problem and iii) the information loss paradox since the outgoing Hawking radiation is entangled with the state inside the black hole which becomes the new universe.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2021)·12 citations
20. 20*

    Measurement methods of radial flow in relativistic heavy-ion collisions

    Peng Yang🇨🇳 · Lin Li🇨🇳 · Yu Zhou🇺🇸 · Zhiming Li🇨🇳 · Mingmei Xu🇨🇳 · Yeyin Zhao🇨🇳 · Yuanfang Wu🇨🇳

    Radial flow can be directly extracted from the azimuthal distribution of mean transverse rapidity. We apply the event-plane method and the two-particle correlation method to estimate the anisotropic Fourier coefficient of the azimuthal distribution of mean transverse rapidity. Using the event sample generated by a multiphase transport model with string melting, we show that both methods are effective. For the two-particle correlation method to be reliable, the mean number of particles in an azimuthal bin must be above a certain threshold. Using these two methods, anisotropic radial flow can be estimated in a model-independent way in relativistic heavy-ion collisions.

    ↳ nucl-thhep-phnucl-exPRC(2021)·1 citation
21. 21*

    Self-Renormalization of Quasi-Light-Front Correlators on the Lattice

    Yi-Kai Huo🇨🇳 · Yushan Su🇺🇸 · Long-Cheng Gui🇨🇳 · Xiangdong Ji🇺🇸 · Yuan-Yuan Li🇨🇳 · Yizhuang Liu🇩🇪 · Andreas Schäfer🇩🇪 · Maximilian Schlemmer🇩🇪 · Peng Sun🇨🇳 · Wei Wang🇨🇳 · Yi-Bo Yang🇨🇳 · Jian-Hui Zhang🇨🇳 · Kuan Zhang🇨🇳

    In applying large-momentum effective theory, renormalization of the Euclidean correlators in lattice regularization is a challenge due to linear divergences in the self-energy of Wilson lines. Based on lattice QCD matrix elements of the quasi-PDF operator at lattice spacing $a$= 0.03 fm $\sim$ 0.12 fm with clover and overlap valence quarks on staggered and domain-wall sea, we design a strategy to disentangle the divergent renormalization factors from finite physics matrix elements, which can be matched to a continuum scheme at short distance such as dimensional regularization and minimal subtraction. Our results indicate that the renormalization factors are universal in the hadron state matrix elements. Moreover, the physical matrix elements appear independent of the valence fermion formulations. These conclusions remain valid even with HYP smearing which reduces the statistical errors albeit reducing control of the renormalization procedure. Moreover, we find a large non-perturbative effect in the popular RI/MOM and ratio renormalization scheme, suggesting favor of the hybrid renormalization procedure proposed recently.

    ↳ hep-lathep-phNPB(2021)·90 citations
22. 22*

    Comparing multi-field primordial feature models with the Planck data

    Matteo Braglia🇮🇹 · Xingang Chen🇺🇸 · Dhiraj Kumar Hazra🇮🇳

    In this paper, we use a complete model of classical primordial standard clocks as an example to develop a methodology of directly comparing numerical predictions from complicated multi-field feature models with the Planck data, including the Planck 2018 Plik unbinned likelihood and the statistically most powerful CamSpec 2020 likelihood for temperature and polarization data. As this two-field inflationary model offers a plethora of primordial feature spectra that represent combinations of sharp and resonance feature signals non-trivially distributed over extended cosmological scales, its data comparison has not been satisfactorily addressed by previous attempts using analytical templates. The method of this paper, consisting of numerical prediction, effective parameter construction and nested sampling data comparison, allows us to efficiently explore every possible spectra from the model. We classify the resulting feature candidates in three different frequency ranges. We use the Bayesian evidences to assess the statistical significance of the candidates over the baseline model, taking into account the effect of additional parameters and the look-elsewhere effect. Although none of the candidates is statistically significant, the methodology of this paper can be used to facilitate the future model-building and data-screening process of primordial features, and the candidates can be subjected to further tests with data from the upcoming cosmic microwave background polarization observations and galaxy surveys.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2021)·46 citations
23. 23*

    How does the Planck scale affect qubits?

    Matthew J. Lake🇨🇳

    Gedanken experiments in quantum gravity motivate generalised uncertainty relations (GURs) implying deviations from the standard quantum statistics close to the Planck scale. These deviations have been extensively investigated for the non-spin part of the wave function but existing models tacitly assume that spin states remain unaffected by the quantisation of the background in which the quantum matter propagates. Here, we explore a new model of nonlocal geometry in which the Planck-scale smearing of classical points generates GURs for angular momentum. These, in turn, imply an analogous generalisation of the spin uncertainty relations. The new relations correspond to a novel representation of {\rm SU(2)} that acts nontrivially on both subspaces of the composite state describing matter-geometry interactions. For single particles each spin matrix has four independent eigenvectors, corresponding to two $2$-fold degenerate eigenvalues $\pm (\hslash +\beta )/2$, where $\beta$ is a small correction to the effective Planck's constant. These represent the spin states of a quantum particle immersed in a quantum background geometry and the correction by $\beta$ emerges as a direct result of the interaction terms. In addition to the canonical qubits states, $|0⟩=|\uparrow ⟩$ and $|1⟩=|\downarrow ⟩$, there exist two new eigenstates in which the spin of the particle becomes entangled with the spin sector of the fluctuating spacetime. We explore ways to empirically distinguish the resulting `geometric' qubits, $|0^{\prime }⟩$ and $|1^{\prime }⟩$, from their canonical counterparts.

    ↳ quant-phgr-qchep-phhep-thQuantum Rep.(2021)·15 citations
24. 24*

    Stability of domain walls in models with asymmetric potentials

    Tomasz Krajewski🇵🇱 · Jan Henryk Kwapisz🇵🇱 · Zygmunt Lalak🇵🇱 · Marek Lewicki🇵🇱

    We study the evolution of cosmological domain walls in models with asymmetric potentials. Our research goes beyond the standard case of spontaneous breaking of an approximate symmetry. When the symmetry is explicitly broken the potential exhibits nearly degenerate minima which can lead to creation of a metastable network of domain walls. The time after which the network will decay depends on the difference of values of the potential in minima, its asymmetry around the maximum separating minima and the bias of the initial distribution of the field. Effect of asymmetry around the maximum separating minima is novel one that we study with a new type of potential. Using numerical lattice simulations we determine relative importance of these factors on decay time of networks for generic potentials. We find that even very small departures from the symmetric initial distribution case lead to rapid decay of the domain wall network. As a result creation of a long lasting network capable of producing observable gravitational wave signals is much more difficult than previously thought. On the other hand details of the shape of the potential turn out to be much less important than was expected and the evolution of network from symmetric distribution is controlled by the difference of values of the potential in the minima.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2021)·36 citations
25. 25*

    Accurate Gaunt factors for non-relativistic quadrupole bremsstrahlung

    Josef Pradler🇦🇹 · Lukas Semmelrock🇦🇹

    The exact result for non-relativistic quadrupole bremsstrahlung in a Coulomb field was established only recently in Pradler & Semmelrock (2020). It requires the evaluation and integration of hypergeometric functions across a wide range of parameters and arguments, which, in practice, is unfeasible. Here we provide a highly accurate tabulation of the Gaunt factor for quadrupole radiation, its thermal average in a Maxwellian plasma, and the associated cooling function over the entire kinematically relevant range. In addition, we provide a simple approximate formula for the emission cross section which works to within a few percent accuracy for all practical purposes. The results can be applied to the scattering of electrons with themselves, for which quadrupole radiation is the dominant process.

    ↳ astro-ph.COhep-phApJ(2021)·7 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.