Wed·Dec 12, 2018Wednesday·December 12, 2018

1. 01*

   Light scalar dark matter coupled to a trace of energy-momentum tensor

   Aleksandr Belokon🇷🇺 · Anna Tokareva🇷🇺

   We consider dark matter represented by the light scalar field whose coupling to the ordinary matter is extremely suppressed. We assume that this interaction can be described as the coupling of the square of the field to the energy-momentum tensor. We study the effect of this interaction on the evolution of dark matter scalar, as well as bounds on the model parameters that come from the variation of fundamental constants at the BBN.

   hep-phPRD(2020)·4 citations
2. 02*

   Non-Standard Neutrino Interactions and Neutral Gauge Bosons

   Julian Heeck🇧🇪 · Manfred Lindner🇩🇪 · Werner Rodejohann🇩🇪 · Stefan Vogl🇩🇪

   We investigate Non-Standard Neutrino Interactions (NSI) arising from a flavor-sensitive $Z^{\prime }$ boson of a new $U(1{)}^{\prime }$ symmetry. We compare the limits from neutrino oscillations, coherent elastic neutrino-nucleus scattering, and $Z^{\prime }$ searches at different beam and collider experiments for a variety of straightforward anomaly-free $U(1{)}^{\prime }$ models generated by linear combinations of $B-L$ and lepton-family-number differences $L_{\alpha }-L_{\beta }$. Depending on the flavor structure of those models it is easily possible to avoid NSI signals in long-baseline neutrino oscillation experiments or change the relative importance of the various experimental searches. We also point out that kinetic $Z$-$Z^{\prime }$ mixing gives vanishing NSI in long-baseline experiments if a direct coupling between the $U(1{)}^{\prime }$ gauge boson and matter is absent. In contrast, $Z$-$Z^{\prime }$ mass mixing generates such NSI, which in turn means that there is a Higgs multiplet charged under both the Standard Model and the new $U(1{)}^{\prime }$ symmetry.

   hep-phhep-exSciPost Phys.(2019)·98 citations
3. 03*

   Observing Thermal Schwinger Pair Production

   Oliver Gould🇫🇮 · Stuart Mangles🇬🇧 · Arttu Rajantie🇬🇧 · Steven Rose🇳🇴 · Cheng Xie🇬🇧

   We study the possibility of observing Schwinger pair production enhanced by a thermal bath of photons. We consider the full range of temperatures and electric field intensities from pure Schwinger production to pure thermal production, and identify the most promising and interesting regimes. In particular, we identify temperatures of $\sim 20\mathrm{keV}/k_B$ and field intensities of $\sim 10^{23}{\mathrm{Wcm}}^{-2}$ where pair production would be observable. In this case, the thermal enhancement over the Schwinger rate is exponentially large and due to effects which are not visible at any finite order in the loop expansion. Pair production in this regime can thus be described as more nonperturbative than the usual Schwinger process, which appears at one loop. Unfortunately, such high temperatures appear to be out of reach of foreseeable technologies, though nonthermal photon distributions with comparable energy densities are possible. We suggest the possibility that similar nonperturbative enhancements may extend out of equilibrium and propose an experimental scheme to test this.

   hep-phphysics.plasm-phPRA(2019)·29 citations
4. 04*

   Leading Loop Effects in Pseudoscalar-Higgs Portal Dark Matter

   Karim Ghorbani🇮🇷 · Parsa Hossein Ghorbani🇺🇸

   We examine a model with a fermionic dark matter candidate having pseudoscalar interaction with the standard model particles where its direct detection elastic scattering cross section at tree level is highly suppressed. We then calculate analytically the leading loop contribution to the spin independent scattering cross section. It turns out that these loop effects are sizable over a large region of the parameter space. Taking constraints from direct detection experiments, the invisible Higgs decay measurements, observed DM relic density, we find viable regions which are within reach in the future direct detection experiments such as XENONnT.

   hep-phJHEP(2019)·24 citations
5. 05*

   Matching relations for decoupling in the Standard Model at two loops and beyond

   Stephen P. Martin🇺🇸

   I discuss the matching relations for the running renormalizable parameters when the heavy particles (top quark, Higgs scalar, Z and W vector bosons) are simultaneously decoupled from the Standard Model. The complete two-loop order matching for the electromagnetic coupling and all light fermion masses are obtained, augmenting existing results at 4-loop order in pure QCD and complete two-loop order for the strong coupling. I also review the further sequential decouplings of the lighter fermions (bottom quark, tau lepton, and charm quark) from the low-energy effective theory.

   hep-phPRD(2019)·14 citations
6. 06*

   Collectivity in pp from resummed interference effects?

   Boris Blok🇮🇱 · Urs Achim Wiedemann🇨🇭

   Azimuthal asymmetries $v_n$ in the soft transverse momentum spectra of hadronic collisions can result as a consequence of quantum interference and color flow which translates spatial anisotropies into momentum anisotropies via multipole radiation patterns. Here, we analyze to what extent these effects result in signal strengths $v_n\{2s\}$ that can persist in higher order $(2s)$ cumulants. In a simple model of soft multi-particle production with quantum interference effects in which $m$ particles are emitted from $N$ sources and in which interference contributions appear naturally ordered in inverse powers of the adjoint color trace, $1/(N_c^2-1)$, we provide the first resummed calculation of all powers of $m^2/(N_c^2-1)$. This allows one to determine all higher order flow cumulants $v_n\{2s\}$ with the same parametric accuracy. For a phenomenologically relevant range of $N$ sources emitting $m$ particles, we find that the even flow coefficients $v_n\{2s\}$ decrease very mildly with increasing cumulants. This provides a proof of principle that non-vanishing higher order cumulants $v_n\{2s\}$ can persist in systems that exhibit neither final state interactions nor phenomena related to high (saturated) initial parton densities.

   hep-phPLB(2019)·20 citations
7. 07*

   Limits on R-parity-violating couplings from Drell-Yan processes at the LHC

   Saurabh Bansal🇺🇸 · Antonio Delgado🇺🇸 · Christopher Kolda🇺🇸 · Mariano Quiros🇪🇸

   We find constraints on R-Parity Violating (RPV) couplings of the minimal supersymmetric standard model, using Drell-Yan differential cross sections at the LHC. Specifically, we look at the constraints on ${\lambda }^{\prime }LQ{D}^c$ couplings from monolepton and dilepton data published by ATLAS, with either electrons or muons in the final state. Out of the 18 RPV couplings to which the LHC is at least potentially sensitive by this technique, we find new limits on 12 (or 13) of them, for squarks masses above 1 (or 2) TeV. We also show that one can employ our techniques to achieve significantly stronger bounds at a high-luminosity upgrade of the LHC.

   hep-phPRD(2019)·14 citations
8. 08*

   Study of $a_1(1260)$ in the $\gamma p\to {\pi }^{+}{\pi }^{+}{\pi }^{-}n$ reaction

   Xu Zhang🇨🇳 · Ju-Jun Xie🇨🇳

   We investigate the discovery potential of the $a_1(1260)$ photoproduction in the $\gamma p\to a_1(1260{)}^{+}n$ and $\gamma p\to {\pi }^{+}{\pi }^{+}{\pi }^{-}n$ reactions via the $\pi$-exchange mechanism. For the $\gamma p\to {\pi }^{+}{\pi }^{+}{\pi }^{-}n$ reaction, we perform a calculation for the differential and total cross sections by including the contributions from the $a_1(1260)$ intermediate resonance decaying into $\rho \pi$ then into ${\pi }^{+}{\pi }^{+}{\pi }^{-}$. Besides, the non-resonance process is also considered. With a lower mass of $a_1(1260)$, we get a fairly good description of the experimental data for the invariant ${\pi }^{+}{\pi }^{+}{\pi }^{-}$ mass distributions. For the $\gamma p\to a_1(1260{)}^{+}n$ reaction, with our model parameters, the total cross section is of the order of 10 $\mu$b at photon beam energy $E_{\gamma }\sim$ 2.5 GeV. It is expected that our model calculations could be tested by future experiments.

   hep-phCPC(2019)·5 citations
9. 09*

   Infrared finiteness of a thermal theory of scalar electrodynamics to all orders

   Pritam Sen (1 and 2)🇮🇳 · D. Indumathi (1 and 2)🇮🇳 · Debajyoti Choudhury (3) ((1) The Institute of Mathematical Sciences, Chennai, (2) Homi Bhabha National Institute, Mumbai, (3) Department of Physics and Astrophysics, University of Delhi, Delhi)🇮🇳

   Models explaining dark matter typically include interactions with charged scalar and fermion fields. The Infra-Red (IR) finiteness of thermal field theories of charged fermions (fermionic QED) has been proven to all orders in perturbation theory. Here we reexamine the IR behaviour of charged scalar theories at finite temperature. Using the method of Grammer and Yennie, we identify and factorise the infra-red divergences to all orders in perturbation theory. The inclusion of IR finite pieces arising from the 4-point interaction terms of scalars with photon fields is key to the exponentiation. We use this in a companion paper to prove the IR finiteness of the corresponding thermal theory which is of relevance in dark matter calculations.

   hep-phastro-ph.COhep-thEPJC(2019)·6 citations
10. 10*

    Double parton scattering and the proton transverse structure at the LHC

    Matteo Rinaldi🇮🇹 · Federico Alberto Ceccopieri🇧🇪

    We consider double parton distribution functions (dPDFs), essential quantities in double parton scattering (DPS) studies, which encode novel non perturbative insight on the partonic proton structure. We develop the formalism to extract this information from dPDFs and present results by using constituent quark model calculations within the Light-Front approach, focusing on radiatively generated gluon dPDFs. Moreover, we generalize the relation between the mean transverse partonic distance between two active partons in a DPS process and the so called effective cross section to include partonic correlations and the so called 2v1 mechanism contribution. Finally we investigate the impact of relativistic effects on digluon distributions and study the structure of the corresponding longitudinal and transverse correlations.

    hep-phnucl-thJHEP(2019)·24 citations
11. 11*

    High-Energy Expansion of Two-Loop Massive Four-Point Diagrams

    Go Mishima🇩🇪

    We apply the method of regions to the massive two-loop integrals appearing in the Higgs pair production cross section at the next-to-leading order, in the high energy limit. For the non-planar integrals, a subtle problem arises because of the indefinite sign of the second Symanzik polynomial. We solve this problem by performing an analytic continuation of the Mandelstam variables such that the second Symanzik polynomial has a definite sign. Furthermore, we formulate the procedure of applying the method of regions systematically. As a by-product of the analytic continuation of the Mandelstam variables, we obtain crossing relations between integrals in a simple and systematic way. In our formulation, a concept of "template integral" is introduced, which represents and controls the contribution of each region. All of the template integrals needed in the computation of the Higgs pair production at the next-to-leading order are given explicitly. We also develop techniques to solve Mellin-Barnes integrals, and show them in detail. Although most of the calculation is shown for the concrete example of the Higgs pair production process, the application to other similar processes is straightforward, and we anticipate that our method can be useful also for other cases.

    hep-phhep-thJHEP(2019)·42 citations
12. 12*

    Low energy neutrinos from stopped muons in the Earth

    Wan-Lei Guo🇨🇳

    We explore the low energy neutrinos from stopped cosmic ray muons in the Earth. Based on the muon intensity at the sea level and the muon energy loss rate, the depth distributions of stopped muons in the rock and sea water can be derived. Then we estimate the ${\mu }^{-}$ decay and nuclear capture probabilities in the rock. Finally, we calculate the low energy neutrino fluxes and find that they depend heavily on the detector depth $d$. For $d=1000$ m, the ${\nu }_e$, ${\bar{\nu }}_e$, ${\nu }_{\mu }$ and ${\bar{\nu }}_{\mu }$ fluxes in the range of 13 MeV $\le E_{\nu }\le$ 53 MeV are averagely $10.8\%$, $6.3\%$, $3.7\%$ and $6.2\%$ of the corresponding atmospheric neutrino fluxes, respectively. The above results will be increased by a factor of 1.4 if the detector depth $d<30$ m. In addition, we find that most neutrinos come from the region within 200 km and the near horizontal direction, and the ${\bar{\nu }}_e$ flux depends on the local rock and water distributions.

    hep-phhep-exPRD(2019)·11 citations
13. 13*

    Update of the extraction of the CKM matrix elements

    Luiz Vale Silva🇬🇧

    I discuss the combination and extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements under the Standard Model (SM) framework from a global fit. The analysis shown here relies on the CKMfitter package, consisting in a frequentist approach that employs the Range fit (Rfit) scheme to handle theoretical uncertainties.

    hep-ph1 citation
14. 14*

    Low-scale leptogenesis assisted by a real scalar singlet

    Tommi Alanne🇩🇪 · Thomas Hugle🇩🇪 · Moritz Platscher🇩🇪 · Kai Schmitz🇮🇹

    Standard thermal leptogenesis in the type-I seesaw model requires very heavy right-handed neutrinos (RHNs). This makes it hard to probe this scenario experimentally and results in large radiative corrections to the Higgs boson mass. In this paper, we demonstrate that the situation is considerably different in models that extend the Higgs sector by a real scalar singlet. Based on effective-theory arguments, the extra scalar is always allowed to couple to the heavy neutrinos via singlet Yukawa terms. This opens up new RHN decay channels leading to larger $CP$ violation as well as to a stronger departure from thermal equilibrium during leptogenesis. As a consequence, the baryon asymmetry can be generated for a lightest RHN mass as low as 500 GeV and without the need for a highly degenerate RHN mass spectrum. In fact, the requirement of successful leptogenesis via the Higgs portal coupling singles out an interesting parameter region that can be probed in on-going and future experiments. We derive a semianalytical fit function for the final baryon asymmetry that allows for an efficient study of parameter space, thus enabling us to identify viable parameter regions. Our results are applicable to a wide range of models featuring an additional real scalar singlet.

    hep-phJCAP(2019)·40 citations
15. 15*

    ${\bar{B}}^{(\ast )}{\bar{B}}^{(\ast )}$ interactions in chiral effective field theory

    Bo Wang🇨🇳 · Zhan-Wei Liu🇨🇳 · Xiang Liu🇨🇳

    In this work, the intermeson interactions of double-beauty $\bar{B}\bar{B}$, $\bar{B}{\bar{B}}^{\ast }$, and ${\bar{B}}^{\ast }{\bar{B}}^{\ast }$ systems have been studied with heavy meson chiral effective field theory. The effective potentials are calculated with Weinberg's scheme up to one-loop level. At the leading order, four body contact interactions and one pion exchange contributions are considered. In addition to two pion exchange diagrams, we include the one-loop chiral corrections to contact terms and one pion exchange diagrams at the next-to-leading order. The behaviours of effective potentials both in momentum space and coordinate space are investigated and discussed extensively. We notice the contact terms play important roles in determining the characteristics of the total potentials. Only the potentials in $I(J^P)=0(1^{+})$ $\bar{B}{\bar{B}}^{\ast }$ and ${\bar{B}}^{\ast }{\bar{B}}^{\ast }$ systems are attractive, and the corresponding binding energies in these two channels are solved to be $\Delta E_{\bar{B}{\bar{B}}^{\ast }}\simeq -12.6_{-12.9}^{+9.2}$ MeV and $\Delta E_{{\bar{B}}^{\ast }{\bar{B}}^{\ast }}\simeq -23.8_{-21.5}^{+16.3}$ MeV, respectively. The masses of $0(1^{+})$ $\bar{B}{\bar{B}}^{\ast }$ and ${\bar{B}}^{\ast }{\bar{B}}^{\ast }$ states lie above the threshold of their electromagnetic decay modes $\bar{B}\bar{B}\gamma$ and $\bar{B}\bar{B}\gamma \gamma$, and thus they can be reconstructable via electromagnetic interactions. Our calculation not only provides some useful information to explore exotic doubly-bottomed molecular states for future experiments, but also is helpful for the extrapolations of Lattice QCD simulations.

    hep-phPRD(2019)·53 citations
16. 16*

    Chiral and $U(1{)}_A$ restoration: Ward Identities and effective theories

    A. Gómez Nicola🇪🇸 · J. Ruiz de Elvira🇨🇭 · A. Vioque-Rodríguez🇪🇸 · S. Ferreres-Solé🇳🇱

    We discuss our recent results regarding chiral and $U(1{)}_A$ restoration, both from the formal point of view of QCD Ward Identities (WI) and from an Effective Theory analysis provided by $U(3)$ Chiral Perturbation Theory (ChPT) at finite temperature. Our results lead to relevant conclusions regarding the behavior of chiral partners (in terms of susceptibilities) in the limit of exact restoration and provide useful results for lattice analysis. In addition, it helps to understand the temperature dependence of lattice screening masses in terms of quark condensate combinations. The U(3) ChPT calculation supports the conclusions obtained within the WI analysis. Finally, the role of the thermal $f_0(500)$ state in chiral symmetry restoration, regarding the scalar susceptibility, is also discussed.

    hep-phPoS(2019)·2 citations
17. 17*

    Geometrical scaling of prompt photons in heavy ion collisions

    Michal Praszalowicz🇵🇱

    We discuss geometrical scaling (GS) for the prompt (direct) photons produced in heavy ion collisions. To this end we first introduce the concept of GS and illustrate its emergence on the example of charged particles. Next, we analyse direct photon data from RHIC and from the LHC. We show that the data support the hypothesis of GS in terms of participant number related to different centrality classes. We also study GS at different energies, however a more detailed study will be possible only when data for at least three different energies from one experiment will be available and also when we use the data obtained from the collisions of large systems (Cu+Cu, Au+Au, Pb+Pb) and small systems (p+p, d+Au, p+Au).

    hep-phnucl-thEPJ Web Conf.(2019)·5 citations
18. 18*

    Single-Transverse-Spin Asymmetries in Exclusive Photo-production of J/psi in Ultra-Peripheral Collisions in the Fixed-Target Mode at the LHC and in the Collider Mode at RHIC

    J.P. Lansberg🇫🇷 · L. Massacrier🇫🇷 · L. Szymanowski🇵🇱 · J. Wagner🇵🇱

    We investigate the potentialities offered by the study of J/psi exclusive photo-production in ultra-peripheral collisions at a fixed-target experiment using the proton and lead LHC beams (generically denoted as AFTER@LHC) on hydrogen targets and at RHIC in the collider mode. We compare the expected counting rates in both set-ups. Studying Single-Transverse-Spin Asymmetries (A_N) in such a process provides a direct path to the proton Generalised Parton Distribution (GPD) E_g(x,xi,t). We evaluate the expected precision on A_N for realistic conditions with the LHCb detector in pH(pol) and PbH(pol) collisions. We also discuss prospects with polarised deuterium and helium targets in the case of AFTER@LHC.

    hep-phhep-exnucl-exnucl-thPLB(2019)·15 citations
19. 19*

    Analytic Form of the Planar Two-Loop Five-Gluon Scattering Amplitudes in QCD

    S. Abreu🇧🇪 · J. Dormans🇩🇪 · F. Febres Cordero🇩🇪 · H. Ita🇩🇪 · B. Page🇫🇷

    We present the analytic form of the two-loop five-gluon scattering amplitudes in QCD for a complete set of independent helicity configurations of external gluons. These include the first analytic results for five-point two-loop amplitudes relevant for the computation of next-to-next-to-leading-order QCD corrections at hadron colliders. The results were obtained by reconstructing analytic expressions from numerical evaluations. The complexity of the computation is reduced by exploiting physical and analytical properties of the amplitudes, employing a minimal basis of so-called pentagon functions that have recently been classified.

    hep-phhep-thPRL(2019)·171 citations
20. 20*

    An Anomaly-free Atlas: charting the space of flavour-dependent gauged $U(1)$ extensions of the Standard Model

    B. C. Allanach🇬🇧 · Joe Davighi🇬🇧 · Scott Melville🇬🇧

    Spontaneously broken, flavour-dependent, gauged $U(1)$ extensions of the Standard Model (SM) have many phenomenological uses. We chart the space of solutions to the gauge anomaly cancellation equations in such extensions, for both the SM chiral fermion content and the SM plus (up to) three right-handed neutrinos (SM${\nu }_R$). Methods from Diophantine analysis allow us to efficiently index the solutions arithmetically, and produce the complete solution space in particular cases. In order to solve the general case, we build a computer program which cycles through possible $U(1)$ charge assignments, providing all solutions for charges up to some pre-defined maximum absolute charge. Lists of anomaly-free $U(1)$ charge assignments result, which corroborate the results of our Diophantine analysis. We make these lists, which may be queried for further desirable properties, publicly available. This previously uncharted space of anomaly-free charge assignments has been little explored until now, paving the way for future model building and phenomenological studies.

    hep-phhep-thJHEP(2019)·121 citations
21. 21*

    Perturbative methods for assisted nonperturbative pair production

    Greger Torgrimsson🇩🇪

    In the dynamically assisted Schwinger mechanism, the pair production probability is significantly enhanced by including a weak, rapidly varying field in addition to a strong, slowly varying field. In a previous paper we showed that several features of dynamical assistance can be understood by a perturbative treatment of the weak field. Here we show how to calculate the prefactors of the higher-orders terms, which is important because the dominant contribution can come from higher orders. We give a new and independent derivation of the momentum spectrum using the worldline formalism, and extend our WKB approach to calculate the amplitude to higher orders. We show that these methods are also applicable to doubly assisted pair production.

    hep-phhep-thPRD(2019)·20 citations
22. 22*

    Long live the Higgs portal!

    Anastasiia Filimonova🇩🇪 · Susanne Westhoff🇩🇪

    In Higgs portal models of fermion dark matter, scalar couplings are unavoidably suppressed by strong bounds from direct detection experiments. As a consequence, thermal dark matter relics must coexist with mediators in a compressed spectrum of dark particles. Small couplings and small mass splittings lead to slow mediator decays, leaving signatures with displaced vertices or disappearing tracks at colliders. We perform a comprehensive analysis of long-lived mediators at the LHC in the context of a minimal dark matter model with a naturally small Higgs portal, also known as the wino-bino scenario in supersymmetry. Existing searches for disappearing charged tracks and displaced hard leptons already exclude tiny portal couplings that cannot be probed by current direct and indirect detection experiments. For larger portal couplings, we predict new signatures with displaced soft leptons, which are accessible with run-II data. Searches for displaced particles are sensitive to weakly coupling mediators with masses up to the TeV scale, well beyond the reach of prompt signals.

    hep-phhep-exJHEP(2019)·35 citations
23. 23*

    Non-singular and ghost-free infinite derivative gravity with torsion

    Álvaro de la Cruz-Dombriz🇿🇦 · Francisco José Maldonado Torralba🇿🇦 · Anupam Mazumdar🇳🇱

    We present the most general quadratic curvature action with torsion including infinite covariant derivatives and study its implications around the Minkowski background via the Palatini approach. Provided the torsion is solely given by the background axial field, the metric and torsion are shown to decouple, and both of them can be made ghost and singularity free for a fermionic source.

    ↳ gr-qchep-phhep-thPRD(2019)·25 citations
24. 24*

    Comment on the paper "On the correlation between the local dark matter and stellar velocities"

    Mariangela Lisanti🇺🇸 · Lina Necib🇺🇸

    We briefly comment on the paper "On the correlation between the local dark matter and stellar velocities" (Bozorgnia et al. 2018), which purports to test our previous claims regarding the correlation of stellar and dark matter kinematics (Herzog-Arbeitman et al. 2017; Necib et al. 2018). The conclusions of these papers are not accurately presented in Bozorgnia et al. (2018), and we thus clarify them here.

    ↳ astro-ph.GAastro-ph.COhep-ph2 citations
25. 25*

    $\gamma W$-box Inside-Out: Nuclear Polarizabilities Distort the Beta Decay Spectrum

    Mikhail Gorchtein🇩🇪

    I consider the $\gamma W$-box correction to superallowed nuclear $\beta$-decays in the framework of dispersion relations. I address a novel effect of a distortion of the emitted electron energy spectrum by nuclear polarizabilities and show that this effect, while neglected in the literature, is sizable. I estimate its size in the approximation of a linear energy dependence, and using two models that are expected to give the lower and the upper bound. The respective correction to the ${\beta }^{+}$ spectrum is estimated to be ${\Delta }_R(E)=(1.6\pm 1.6)\times 10^{-4}E/\mathrm{MeV}$ assuming a conservative 100\% uncertainty. The effect is positive-definite and can be observed if a high-precision measurement of the positron spectrum is viable. If only the full rate is observed, it should be included in the calculated $\mathcal{F}t$-values of nuclear decays. I argue that this novel effect should be evaluated in state-of-the-art nuclear models and included in the analyses of nuclear beta decay experiments to ensure the correct extraction of $V_{ud}$ from decay rates, and of the Fierz interference term from precision measurements of decay spectra.

    ↳ nucl-thhep-phnucl-exPRL(2019)·109 citations
26. 26*

    Upper bound on the radii of regular ultra-compact star photonspheres

    Yan Peng🇨🇳

    We investigate the photonsphere in the background of regular asymptotically flat compact stars. The analysis includes the general hairy compact star considering the matter fields' backreaction on the metric in various gravity theories. We prove that the photonsphere of the compact star has an upper bound expressed in terms of the ADM mass of the spacetime. In the case of negative isotropic trace, a stronger upper bound can be obtained.

    ↳ gr-qchep-phhep-thPLB(2019)·13 citations
27. 27*

    Holographic Superconductors: An Analytic Method Revisit

    En-Jui Chang🇹🇼 · Chia-Jui Chou🇹🇼 · Yi Yang🇹🇼

    We study a non-minimal holographic superconductors model in both non-backreaction and fullbackreaction cases using an analytic method. We calculate the condensate of the dilaton and the critical temperature of the phase transition. We also study the properties of the electric conductivity in various parameters.

    ↳ hep-thhep-phNPB(2020)·3 citations
28. 28*

    Search for the QCD Critical Point by Transverse Velocity Dependence of Anti-deuteron to Deuteron Ratio

    Ning Yu🇨🇳 · Dingwei Zhang🇨🇳 · Xiaofeng Luo🇨🇳

    We propose the transverse velocity (${\beta }_T$) dependence of the anti-deuteron to deuteron ratio as a new observable to search for the QCD critical point in heavy-ion collisions. The QCD critical point can attract the system evolution trajectory in the QCD phase diagram, which is known as focusing effect. To quantify this effect, we employ thermal model and hadronic transport model to simulate the dynamical particle emission along a hypothetical focusing trajectory near critical point. We found the focusing effect can lead to anomalous ${\beta }_T$ dependence of $\bar{p}/p$, $\bar{d}/d$ and ${}^3\overline{\text{He}}{/}^3\text{He}$ ratios. We examined the ${\beta }_T$ dependence of $\bar{p}/p$ and $\bar{d}/d$ ratios of central Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7 to 200 GeV measured by the STAR experiment at RHIC. Surprisingly, we only observe a negative slope in ${\beta }_T$ dependence of $\bar{d}/d$ ratio at $\sqrt{s_{NN}}$ = 19.6 GeV, which indicates the trajectory evolution has passed through the critical region. In the future, we could constrain the location of the critical point and/or width of the critical region by making precise measurements on the ${\beta }_T$ dependence of $\bar{d}/d$ ratio at different energies and rapidity.

    ↳ nucl-thhep-phnucl-exCPC(2020)·26 citations
29. 29*

    Uniform Perpendicular and Parallel Staggered Susceptibility of Antiferromagnetic Films

    Christoph Peter Hofmann🇲🇽

    We investigate the thermodynamic behavior of antiferromagnetic films in external magnetic fields oriented perpendicular to the staggered magnetization. Within the systematic effective Lagrangian framework we first calculate the two-point function and the dispersion relation for the two types of magnons up to one-loop order. This allows us to split the two-loop free energy density into a piece that originates from noninteracting dressed magnons, and a second piece that corresponds to the genuine magnon-magnon interaction. We then discuss the low-temperature series for various thermodynamic quantities, including the parallel staggered and uniform perpendicular susceptibilities, and analyze the role of the spin-wave interaction at finite temperature.

    ↳ cond-mat.str-elhep-lathep-phPhysica B: Physics of Condensed Matter(2020)·3 citations
30. 30*

    Dynamics of junctions and the multi-tension velocity-dependent one-scale model

    I. Yu. Rybak🇵🇹 · A. Avgoustidis🇬🇧 · C. J. A. P. Martins🇵🇹

    The dynamics of string junctions and their influence on the evolution of cosmic superstring networks are studied in full detail. We review kinematic constraints for colliding strings in a Friedmann-Lemaître-Robertson-Walker background and obtain the average distribution of possible string configurations after string collisions. The study of small-scale structure enables us to investigate the average growth/reduction rate of string junctions for a given cosmic string network. Incorporating the averaged junction dynamics into the velocity-dependent one-scale model for multi-tension string networks, we improve the semi-analytic description and quantitative understanding of cosmic superstring network evolution.

    ↳ astro-ph.COhep-phPRD(2019)·8 citations
31. 31*

    The Vacuum Emission Picture Beyond Paraxial Approximation

    Alexander Blinne🇩🇪 · Holger Gies🇩🇪 · Felix Karbstein🇩🇪 · Christian Kohlfürst🇩🇪 · Matt Zepf🇩🇪

    Optical signatures of the effective nonlinear couplings among electromagnetic fields in the quantum vacuum can be conveniently described in terms of stimulated photon emission processes induced by strong classical, space-time dependent electromagnetic fields. Recent studies have adopted this approach to study collisions of Gaussian laser pulses in paraxial approximation. The present study extends these investigations beyond the paraxial approximation by using an efficient numerical solver for the classical input fields. This new numerical code allows for a consistent theoretical description of optical signatures of QED vacuum nonlinearities in generic electromagnetic fields governed by Maxwell's equations in the vacuum, such as manifestly non-paraxial laser pulses. Our code is based on a locally constant field approximation of the Heisenberg-Euler effective Lagrangian. As this approximation is applicable for essentially all optical high-intensity laser experiments, our code is capable of calculating signal photon emission amplitudes in completely generic input field configurations, limited only by numerical cost.

    ↳ physics.opticshep-phquant-phJ.Phys.Conf.Ser.(2019)·7 citations
32. 32*

    ETHOS - an effective theory of structure formation: formation of the first haloes and their stars

    Mark R. Lovell (1,2)🇮🇸 · Jesús Zavala (1)🇮🇸 · Mark Vogelsberger (3) ((1) University of Iceland, (2) Durham, (3) MIT)🇺🇸

    A cutoff in the linear matter power spectrum at dwarf galaxy scales has been shown to affect the abundance, formation mechanism and age of dwarf haloes and their galaxies at high and low redshift. We use hydrodynamical simulations of galaxy formation within the ETHOS framework in a benchmark model that has such a cutoff, and that has been shown to be an alternative to the cold dark matter (CDM) model that alleviates its dwarf-scale challenges. We show how galaxies in this model form differently to CDM on a halo-by-halo basis, at redshifts $z\ge 6$. We show that ETHOS haloes at the half-mode mass scale form with 50~per~cent less mass than their CDM counterparts due to their later formation times, yet they retain more of their gas reservoir due to the different behaviour of gas and dark matter during the monolithic collapse of the first haloes in models with a galactic-scale cutoff. As a result, galaxies in ETHOS haloes near the cutoff scale grow rapidly between $z=10-6$ and by $z=6$ end up having very similar stellar masses, higher gas fractions and higher star formation rates relative to their CDM counterparts. We highlight these differences by making predictions for how the number of galaxies with old stellar populations is suppressed in ETHOS for both $z=6$ galaxies and for gas-poor Local Group fossil galaxies. Interestingly, we find an age gradient in ETHOS between galaxies that form in high and low density environments.

    ↳ astro-ph.GAastro-ph.COhep-phMNRAS(2019)·20 citations

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