Thu·Mar 7, 2019Thursday·March 7, 2019

1. 01*

   Axion Dark Matter Search with Interferometric Gravitational Wave Detectors

   Koji Nagano🇯🇵 · Tomohiro Fujita🇯🇵 · Yuta Michimura🇯🇵 · Ippei Obata🇯🇵

   Axion dark matter differentiates the phase velocities of the circular-polarized photons. In this Letter, a scheme to measure the phase difference by using a linear optical cavity is proposed. If the scheme is applied to the Fabry-Pérot arm of Advanced LIGO-like (Cosmic-Explorer-like) gravitational wave detector, the potential sensitivity to the axion-photon coupling constant, $g_{\text{a}\gamma }$, reaches $g_{\text{a}\gamma }\simeq 8\times 10^{-13}$ GeV${}^{-1}(4\times 10^{-14}$ GeV${}^{-1})$ at the axion mass $m\simeq 3\times 10^{-13}$ eV ($2\times 10^{-15}$ eV) and remains at around this sensitivity for 3 orders of magnitude in mass. Furthermore, its sensitivity has a sharp peak reaching $g_{\text{a}\gamma }\simeq 10^{-14}$ GeV${}^{-1}$ $(8\times 10^{-17}$ GeV${}^{-1})$ at $m=1.563\times 10^{-10}$ eV ($1.563\times 10^{-11}$ eV). This sensitivity can be achieved without loosing any sensitivity to gravitational waves.

   hep-phastro-ph.COastro-ph.IMphysics.ins-det+1PRL(2019)·121 citations
2. 02*

   A robust anomaly finder based on autoencoders

   Tuhin S. Roy🇮🇳 · Aravind H. Vijay🇮🇳

   We propose a robust method to identify anomalous jets by vetoing QCD-jets. The robustness of this method ensures that the distribution of the proposed discriminating variable (which allows us to veto QCD-jets) remains unaffected by the phase space of QCD-jets, even if they were different from the region on which the model was trained. This suggests that our method can be used to look for anomalous jets in high m/p T bins by simply training on jets from low m/p T bins, where sufficient background-enriched data is available. The robustness follows from combining an autoencoder with a novel way of pre-processing jets. We use momentum rescaling followed by a Lorentz boost to find the frame of reference where any given jet is characterized by predetermined mass and energy. In this frame we generate jet images by constructing a set of orthonormal basis vectors using the Gram-Schmidt method to span the plane transverse to the jet axis. Due to our preprocessing, the autoencoder loss function does not depend on the initial jet mass, momentum or orientation while still offering remarkable performance. We also explore the application of this loss function combined (using supervised learning techniques like boosted decision trees) with few other jet observables like the mass and Nsubjettiness for the purpose of top tagging. This exercise shows that our method performs almost as well as existing top taggers which use a large amount of physics information associated with top decays while also reinforcing the fact that the loss function is mostly independent of the additional jet observables.

   hep-phhep-ex100 citations
3. 03*

   Analytic Solution of Multi-Dimensional Schrodinger in Hot and Dense QCD Media Using SUSYQM Method

   M. Abu-Shady🇪🇬 · A. N. Ikot🇳🇬

   The N-radial Schrödinger equation is analytically solved by using SUSYQM method, in which the heavy quarkonia potential is introduced at finite temperature and baryon chemical potential. The energy eigenvalue is calculated in the N-dimensional space. The obtained results show that the binding energy strongly decreases with increasing temperature and is slightly sensitive for changing baryon chemical potential up to 0.6 GeV at higher values of temperatures. We employed the nonperturbative corrections to the leading-order of the Debye mass at finite baryon chemical potential. We found that the binding energy is more dissociates when the nonperturbative corrections are included with the leading-order term of Debye mass in both hot and dense media. A comparison is discussed with other works such as the lattice parameterized of Debye mas. Thus, the present potential with the SUSYQM method provides satisfying results for the description of the dissociation of binding energy for heavy quarkonia in hot and dense media.

   hep-phnucl-thEur.Phys.J.Plus(2019)·26 citations
4. 04*

   Theory Predictions for the Pull Angle

   Andrew J. Larkoski🇺🇸 · Simone Marzani🇮🇹 · Chang Wu🇮🇹

   Pull is a jet observable that is sensitive to color flow between dipoles. It has seen wide use for discrimination of particles with similar decay topologies but carrying different color representations and has been measured on W bosons from top quark decays by the D$\varnothing$ and ATLAS experiments. In this paper, we present the first theoretical predictions of pull, focusing on a color-singlet decaying in two jets. The pull angle observable is particularly sensitive to color flow, but is not infrared and collinear safe and so cannot be calculated in fixed-order perturbation theory. Nevertheless, all-orders resummation renders its distribution finite, a property referred to as Sudakov safety. In our prediction of the pull angle we also include an estimation of the effects from hadronization, and directly compare our results to simulation and experimental data.

   hep-phPRD(2019)·15 citations
5. 05*

   The mass spectra and wave functions for the doubly heavy baryons with $J^P=1^{+}$ heavy diquark core

   Qiang Li🇨🇳 · Chao-Hsi Chang🇨🇳 · Si-Xue Qin🇨🇳 · Guo-Li Wang🇨🇳

   The mass spectra and wave functions for the doubly heavy baryons are computed under the picture that the two heavy quarks inside a doubly heavy baryon, such as two $c$-quarks in ${\Xi }_{cc}$, combine into a heavy `diquark core' in color anti-triplet firstly, then the diquark core turns into a color-less doubly heavy baryon via combining the light $q$-quark inside the baryon. Namely both of the combinations, the two heavy quarks inside the baryon into a diquark core in color anti-triplet and the heavy diquark core with the light quark into the baryon, are depicted by relativistic Bethe-Salpeter equations (BSEs) with an accordingly QCD inspired kernel respectively, although in the paper only the heavy diquark cores with the quantum numbers $J^P=1^{+}$ are considered. Since the `second combination' is of the heavy diquark core and the light quark, so the structure effect of the diquark core to the relevant kernel of the BSE is specially considered in terms of the diquark-core wave functions. The mass spectra and wave functions for the `low-laying' doubly heavy baryons in the flavors $(ccq)$, $(bcq)$ and $(bbq)$ and in the quantum numbers $J^P={\frac{1}{2}}^{+}$, $J^P={\frac{3}{2}}^{+}$, achieved by solving the equations under the so-called instantaneous approximation, are presented properly and some comparisons with the others' results under different approaches in the literature are made.

   hep-phCPC(2020)·42 citations
6. 06*

   On the vanishing of certain cuts or residues of loop integrals with higher powers of the propagators

   Robin Baumeister🇩🇪 · Daniel Mediger🇩🇪 · Julia Pečovnik🇩🇪 · Stefan Weinzierl🇩🇪

   Starting from two-loops, there are Feynman integrals with higher powers of the propagators. They arise from self-energy insertions on internal lines. Within the loop-tree duality approach or within methods based on numerical unitarity one needs (among other things) the residue when a raised propagator goes on-shell. We show that for renormalised quantities in the on-shell scheme these residues can be made to vanish already at the integrand level.

   hep-phPRD(2019)·23 citations
7. 07*

   Bayesian techniques and applications to QCD

   Alexander Rothkopf🇳🇴

   Realizing the full potential of interconnecting the large amounts of data created in physics experiments, phenomenological models and theory simulations requires robust tools for statistical inference. Here I review a particularly promising branch, Bayesian statistics, which over the past decade has found manifold use in high-energy physics. After a brief introduction to Bayesian statistics I will present two concrete examples, where Bayesian thinking has led to progress in understanding strongly interacting matter: unfolding problems in the form of lattice QCD spectral functions (in spirit similar to detector corrections), as well as the efficient estimation of quark-gluon-plasma parameters from a systematic comparison of experimental heavy-ion collision data and phenomenological models.

   hep-phnucl-thphysics.data-anPoS(2018)·12 citations
8. 08*

   Hadron tomography for pion and its gravitational form factors

   Qin-Tao Song🇯🇵

   Generalized parton distributions (GPDs) are three-dimensional structure functions of hadrons, and they can reveal the orbital-angular-momentum contributions to the nucleon spin. Therefore, GPDs are important for solving the proton spin puzzle. The generalized distribution amplitudes (GDAs) are the $s$-$t$ crossed quantities of the GPDs, and the GDAs can be investigated in two-photon process (${\gamma }^{\ast }\gamma \to h\bar{h}$) which is accessible at KEKB. The pion GDAs were obtained by analyzing the Belle measurements for ${\pi }^0{\pi }^0$ production in the $e^{+}{e}^{-}$ collision. From the obtained GDAs, the form factors of energy-momentum tenor were calculated for pion in the timelike region. In order to study the gravitational radii for the pion, the form factors of energy-momentum tenor were obtained in the spacelike region by using the dispersion relation. Then, the mass radius was calculated as 0.32 $\sim$ 0.39 fm and the mechanical radius was also estimated for the pion as 0.82 $\sim$ 0.88 fm by using the spacelike form factors. This is the first finding on gravitational form factors and radii of hadrons from actual experimental measurements. In the near future we can expect more precise measurements of ${\gamma }^{\ast }\gamma \to h\bar{h}$ as the Belle II started data taking by the higher luminosity Super KEKB, so that the GDAs of other hadrons could be studied as well.

   hep-phhep-exhep-latnucl-thJPS Conf.Proc.(2019)·1 citation
9. 09*

   Convergence of the light-front coupled-cluster method in quenched scalar Yukawa theory

   Sophia S. Chabysheva · John R. Hiller

   We explore the convergence of the light-front coupled-cluster (LFCC) method in the context of two-dimensional quenched scalar Yukawa theory. This theory is simple enough for higher-order LFCC calculations to be relatively straightforward. The quenching is to maintain stability; the spectrum of the full theory with pair creation and annihilation is unbounded from below. The basic interaction in the quenched theory is only emission and absorption of a neutral scalar by the complex scalar. The LFCC method builds the eigenstate with one complex scalar and a cloud of neutrals from a valence state that is just the complex scalar and the action of an exponentiated operator that creates neutrals. The lowest order LFCC operator creates one; we add the next order, a term that creates two. At this order there is a direct contribution to the wave function for two neutrals and one complex scalar and additional contributions to all higher Fock wave functions from the exponentiation. Results for the lowest order and this new second-order approximation are compared with those obtained with standard Fock-state expansions. The LFCC approach is found to allow representation of the eigenstate with far fewer functions than the number of wave functions required in a converged Fock-state expansion.

   hep-phPRD(2019)·2 citations
10. 10*

    Cornering top-philic dark matter with colliders and cosmology: the importance of QCD corrections

    Benjamin Fuks🇫🇷

    Constraining dark matter models necessitates accurate predictions for large set of observables originating from collider physics, cosmology and astrophysics. We consider two classes of top-philic dark matter models where the dark sector is coupled to the Standard Model via the top quark and study the complementarity of dark matter relic density, direct and indirect detection and collider searches in exploring the model parameter space. We moreover investigate how higher-order corrections affect the results.

    hep-phJ.Phys.Conf.Ser.(2019)·2 citations
11. 11*

    Scalar phenomenology in type-II seesaw model

    R. Primulando🇮🇩 · J. Julio🇮🇩 · P. Uttayarat🇹🇭

    In this work we study the viable parameter space of the scalar sector in the type-II seesaw model. In identifying the allowed parameter space, we employ constraints from low energy precision measurements, theoretical considerations and the 125-GeV Higgs data. These tools prove effective in constraining the model parameter space. Moreover, the triplet also offers a rich collider phenomenology from having additional scalars that have unique collider signatures. We find that direct collider searches for these scalars can further probe various parts of the viable parameter space. These parts can be parametrized by the electroweak scalar triplet vacuum expectation value, the mass splitting of the singly- and doubly-charged scalars, and the doubly-charged Higgs mass. We find that different regions of the viable parameter space give rise to different collider signatures, such as the same-sign dilepton, the same-sign $W$ and the multilepton signatures. By investigating various LEP and LHC measurements, we derive the most updated constraints over the whole range of parameter space of the type-II seesaw model.

    hep-phhep-exJHEP(2019)·75 citations
12. 12*

    Machine Learning Templates for QCD Factorization in the Search for Physics Beyond the Standard Model

    Joshua Lin🇺🇸 · Wahid Bhimji🇺🇸 · Benjamin Nachman🇺🇸

    High-multiplicity all-hadronic final states are an important, but difficult final state for searching for physics beyond the Standard Model. A powerful search method is to look for large jets with accidental substructure due to multiple hard partons falling within a single jet. One way for estimating the background in this search is to exploit an approximate factorization in quantum chromodynamics whereby the jet mass distribution is determined only by its kinematic properties. Traditionally, this approach has been executed using histograms constructed in a background-rich region. We propose a new approach based on Generative Adversarial Networks (GANs). These neural network approaches are naturally unbinned and can be readily conditioned on multiple jet properties. In addition to using vanilla GANs for this purpose, a modification to the traditional WGAN approach has been investigated where weight clipping is replaced with a naturally compact set (in this case, the circle). Both the vanilla and modified WGAN approaches significantly outperform the histogram method, especially when modeling the dependence on features not used in the histogram construction. These results can be useful for enhancing the sensitivity of LHC searches to high-multiplicity final states involving many quarks and gluons and serve as a useful benchmark where GANs may have immediate benefit to the HEP community.

    hep-phhep-exJHEP(2019)·38 citations
13. 13*

    Littlest Inverse Seesaw Model

    A. E. Cárcamo Hernández🇨🇱 · S. F. King🇬🇧

    We propose a minimal predictive inverse seesaw model based on two right-handed neutrinos and two additional singlets, leading to the same low energy neutrino mass matrix as in the Littlest Seesaw (LS) (type I) model. In order to implement such a Littlest Inverse Seesaw (LIS) model, we have used an $S_4$ family symmetry, together with other various symmetries, flavons and driving fields. The resulting LIS model leads to an excellent fit to the low energy neutrino parameters, including the prediction of a normal neutrino mass ordering, exactly as in the usual LS model. However, unlike the LS model, the LIS model allows charged lepton flavour violating (CLFV) processes and lepton conversion in nuclei within reach of the forthcoming experiments.

    hep-phNPB(2020)·39 citations
14. 14*

    CP Violation in ${\bar{B}}^0\to D^{\ast +}{\mu }^{-}{\bar{\nu }}_{\mu }$

    Bhubanjyoti Bhattacharya🇺🇸 · Alakabha Datta🇺🇸 · Saeed Kamali🇺🇸 · David London🇨🇦

    In order to explain the observed anomalies in the measurements of $R_{D^{(\ast )}}$ and $R_{J/\psi }$, a variety of new-physics (NP) models that contribute to $b\to c{\tau }^{-}\bar{\nu }$ have been proposed. In this paper, we show how CP-violating observables can be used to distinguish these NP models. Because ${\vec{p}}_{\tau }$ cannot be measured (the decay products of the $\tau$ include the undetected ${\nu }_{\tau }$), obtaining the angular distribution of ${\bar{B}}^0\to D^{\ast +}{\tau }^{-}{\bar{\nu }}_{\tau }$ is problematic. Instead, we focus here on ${\bar{B}}^0\to D^{\ast +}(\to D^0{\pi }^{+}){\mu }^{-}{\bar{\nu }}_{\mu }$. This process may also receive contributions from the same NP, and LHCb intends to measure the CP-violating angular asymmetries in this decay. There are two classes of NP models that contribute to $b\to c{\mu }^{-}{\bar{\nu }}_{\mu }$. These involve (i) a $W^{\prime }$ (two types) or (ii) a leptoquark (LQ) (six types). The most popular NP models predict no CP-violating effects, so the measurement of nonzero CP-violating symmetries would rule them out. Furthermore these measurements allow one to distinguish the $W^{\prime }$ and LQ models, and to differentiate among several LQ models.

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

    Heavy neutrino searches at future $Z$-factories

    Jian-Nan Ding🇨🇳 · Qin Qin🇩🇪 · Fu-Sheng Yu🇨🇳

    We analyze the capacity of future $Z$-factories to search for heavy neutrinos with their mass from 10 to 85 GeV. The heavy neutrinos $N$ are considered to be produced via the process $e^{+}{e}^{-}\to Z\to \nu N$ and to decay into an electron or muon and two jets. By means of Monte Carlo simulation of such signal events and the Standard Model background events, we obtain the upper bounds on the cross sections $\sigma (e^{+}{e}^{-}\to \nu N\to \nu \ell jj)$ given by the $Z$-factories with integrated luminosities of 0.1, 1 and 10 ab${}^{-1}$ if no signal events are observed. Under the assumption of a minimal extension of the Standard Model in the neutrino sector, we also present the corresponding constraints on the mixing parameters of the heavy neutrinos with the Standard Model leptons, and find they are improved by at least one order compared to current experimental constraints.

    hep-phhep-exEPJC(2019)·24 citations
16. 16*

    Discovering heavy U(1)-gauged Higgs bosons at the HL-LHC

    Daniel A. Camargo🇧🇷 · Michael Klasen🇩🇪 · Sybrand Zeinstra🇩🇪

    We determine the discovery potential of the Large Hadron Collider (LHC) at 13 TeV center-of-mass energy for a heavy scalar resonance in the dilepton channel. In particular, we consider the singlet-like heavy mass eigenstate of a mixed two Higgs doublet and scalar singlet model in the $U(1{)}_{B-L}$ extension of the Standard Model. We find that, despite the small coupling of the singlet scalar with the doublets, this heavy scalar can be discovered with 5$\sigma$ at the LHC with integrated luminosities of $\sim 300$ to $1400$ fb${}^{-1}$ in the mass range between 500 GeV and 1 TeV.

    hep-phJ.Phys.G(2020)·4 citations
17. 17*

    Inflation meets neutrinos

    Gabriela Barenboim🇪🇸 · Peter B. Denton🇺🇸 · Isabel M. Oldengott🇪🇸

    Constraints on inflationary models typically assume only the standard models of cosmology and particle physics. By extending the neutrino sector to include a new interaction with a light scalar mediator ($m_{\varphi }\sim$MeV), it is possible to relax these constraints, in particular via opening up regions of the parameter space of the spectral index $n_s$. These new interactions can be probed at IceCube via interactions of astrophysical neutrinos with the Cosmic Neutrino Background for nearly all of the relevant parameter space.

    ↳ astro-ph.COastro-ph.HEhep-phPRD(2019)·93 citations
18. 18*

    Electromagnetic couplings of pentaquarks

    E. Ortiz-Pacheco🇲🇽 · R. Bijker🇲🇽

    In this contribution, we discuss the electromagnetic couplings of pentaquark states with hidden charm. This work is motivated by recent experiments at CERN by the LHCb Collaboraton and current experiments at JLab to confirm the existence of hidden-charm pentaquarks in photoproduction experiments.

    ↳ nucl-thhep-exhep-phnucl-exJ.Phys.Conf.Ser.(2019)·0 citations
19. 19*

    Semi-leptonic form factors for $B_s\to K\ell \nu$ and $B_s\to D_s\ell \nu$

    Jonathan M. Flynn🇬🇧 · Ryan C. Hill🇬🇧 · Andreas Jüttner🇬🇧 · Amarjit Soni🇺🇸 · Justus Tobias Tsang🇬🇧 · Oliver Witzel🇺🇸

    Semi-leptonic $B_s\to K\ell \nu$ and $B_s\to D_s\ell \nu$ decays provide an alternative $b$-decay channel to determine the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$ or to obtain $R$-ratios to investigate lepton flavor universality violations. In addition, these decays may shed further light on the discrepancies seen in the analysis of inclusive vs. exclusive decays. Using the nonperturbative methods of lattice QCD, theoretical results are obtained with good precision and full control over systematic uncertainties. This talk will highlight ongoing efforts of the $B$-physics program by the RBC-UKQCD collaboration.

    ↳ hep-lathep-phPoS(2019)·11 citations
20. 20*

    In-medium heavy quarkonium from lattice NRQCD

    Seyong Kim🇰🇷 · Peter Petreczky🇺🇸 · Alexander Rothkopf🇳🇴

    We present the final results from a multi-year study of the in-medium spectral properties of heavy quarkonium bound states on the lattice. In this work we combine high statistics $N_f=2+1$ ensembles from the HotQCD collaboration with the effective theory NRQCD and improved Bayesian spectral reconstruction methods. We corroborate with high precision the hierarchical in-medium modification of quarkonium states with respect to their vacuum binding energy and provide updated values on melting temperatures. In particular we are able to understand previous disagreements between different Bayesian methods as resulting from underestimated systematic uncertainties. The main quantitative result is a robust determination of the in-medium mass shifts of quarkonium ground states, which we find are negative, consistent with the behavior observed in strongly coupled pNRQCD potential based computations.

    ↳ hep-lathep-phnucl-thPoS(2019)·0 citations
21. 21*

    Volume fluctuation and multiplicity correlation on higher-order cumulants

    Tetsuro Sugiura🇯🇵 · Toshihiro Nonaka🇨🇳 · ShinIchi Esumi🇯🇵

    Initial volume fluctuation (VF) arising from the participant fluctuation would be the background which should be subtracted experimentally from the measured higher-order cumulants. We study the validity of the Volume Fluctuation Correction (VFC) on higher-order net-proton cumulants by using simple toy model and UrQMD model in Au+Au collisions at \sqrt s_{NN} = 200 GeV for various centrality definitions. The results are compared to the conventional data driven method called Centrality Bin Width Correction (CBWC). We find VFC works well in toy model assuming independent particle production (IPP), but does not seem to work well in UrQMD model. It is also found that cumulants are strongly affected by the multiplicity correlation effect as well as the centrality resolution effect. These results show that neither VFC nor CBWC are perfect method. Thus, both methods should be compared in the real experiment.

    ↳ nucl-thhep-exhep-phPRC(2019)·25 citations
22. 22*

    Two roads to antispacetime in polar distorted B phase: Kibble wall and half-quantum vortex

    G.E. Volovik🇫🇮

    We consider the emergent tetrad gravity and the analog of antispacetime realized in the recent experiments ( J.T. Makinen, et al., Nat. Comm. 10, 237 (2019)) on the composite defects in superfluid ${}^3$He: the Kibble walls bounded by strings (the half quantum vortices). The antispacetime can be reached in two different ways: by the "safe" route around the Alice string or by dangerous route across the Kibble wall. This consideration also suggests the scenario of the formation of the discrete symmetry -- the parity $P$ in Dirac equations -- from the continuous symmetry existing on the more fundamental level.

    ↳ cond-mat.othergr-qchep-phJETP Lett.(2019)·6 citations
23. 23*

    DijetGAN: A Generative-Adversarial Network Approach for the Simulation of QCD Dijet Events at the LHC

    Riccardo Di Sipio🇨🇦 · Michele Faucci Giannelli🇬🇧 · Sana Ketabchi Haghighat🇨🇦 · Serena Palazzo🇬🇧

    A Generative-Adversarial Network (GAN) based on convolutional neural networks is used to simulate the production of pairs of jets at the LHC. The GAN is trained on events generated using MadGraph5 + Pythia8, and Delphes3 fast detector simulation. We demonstrate that a number of kinematic distributions both at Monte Carlo truth level and after the detector simulation can be reproduced by the generator network with a very good level of agreement. The code can be checked out or forked from the publicly accessible online repository https://gitlab.cern.ch/disipio/DiJetGAN .

    ↳ hep-exhep-phJHEP(2019)·141 citations
24. 24*

    A Robust Excess in the Cosmic-Ray Antiproton Spectrum: Implications for Annihilating Dark Matter

    Ilias Cholis🇺🇸 · Tim Linden🇺🇸 · Dan Hooper🇺🇸

    An excess of $\sim$10-20 GeV cosmic-ray antiprotons has been identified in the spectrum reported by the AMS-02 Collaboration. The systematic uncertainties associated with this signal, however, have made it difficult to interpret these results. In this paper, we revisit the uncertainties associated with the time, charge and energy-dependent effects of solar modulation, the antiproton production cross section, and interstellar cosmic-ray propagation. After accounting for these uncertainties, we confirm the presence of a 4.7$\sigma$ antiproton excess, consistent with that arising from a $m_{\chi }\approx 64-88$ GeV dark matter particle annihilating to $b\bar{b}$ with a cross section of $\sigma v\simeq (0.8-5.2)\times 10^{-26}$ cm${}^3$/s. If we allow for the stochastic acceleration of secondary antiprotons in supernova remnants, the data continues to favor a similar range of dark matter models ($m_{\chi }\approx 46-94$ GeV, $\sigma v\approx (0.7-3.8)\times 10^{-26}$ cm${}^3/$s) with a significance of 3.3$\sigma$. The same range of dark matter models that are favored to explain the antiproton excess can also accommodate the excess of GeV-scale gamma rays observed from the Galactic Center.

    ↳ astro-ph.HEastro-ph.COhep-phPRD(2019)·196 citations
25. 25*

    Early Cosmological Evolution of Primordial Electromagnetic Fields

    Takeshi Kobayashi🇮🇹 · Martin S. Sloth🇩🇰

    It is usually assumed that when Weyl invariance is unbroken in the electromagnetic sector, the energy density of primordial magnetic fields will redshift as radiation. Here we show that primordial magnetic fields do not exhibit radiation-like redshifting in the presence of stronger electric fields, as a consequence of Faraday's law of induction. In particular for the standard Maxwell theory, magnetic fields on super-horizon scales can redshift as $B^2\propto a^{-6}{H}^{-2}$, instead of the usually assumed $a^{-4}$. Taking into account this effect for inflationary magnetogenesis can correct previous estimates of the magnetic field strength by up to 37 orders of magnitude. This opens new possibilities for inflationary magnetogenesis, and as an example we propose a scenario where femto-Gauss intergalactic magnetic fields are created on Mpc scales, with high-scale inflation producing observable primordial gravitational waves, and reheating happening at low temperatures.

    ↳ astro-ph.COhep-phhep-thPRD(2019)·64 citations
26. 26*

    Analytic Coupling Structure of Large $N_f$ (Super) QED and QCD

    Nicola Andrea Dondi🇩🇰 · Gerald V. Dunne🇺🇸 · Manuel Reichert🇩🇰 · Francesco Sannino🇩🇰

    We study the analytic properties of the 't Hooft coupling expansion of the beta-function at the leading nontrivial large-$N_f$ order for QED, QCD, Super QED and Super QCD. For each theory, the 't Hooft coupling expansion is convergent. We discover that an analysis of the expansion coefficients to roughly 30 orders is required to establish the radius of convergence accurately, and to characterize the (logarithmic) nature of the first singularity. We study summations of the beta-function expansion at order $1/N_f$, and identify the physical origin of the singularities in terms of iterated bubble diagrams. We find a common analytic structure across these theories, with important technical differences between supersymmetric and non-supersymmetric theories. We also discuss the expected structure at higher orders in the $1/N_f$ expansion, which will be in the future accessible with the methods presented in this work, meaning without the need for resumming the perturbative series. Understanding the structure of the large-$N_f$ expansion is an essential step towards determining the ultraviolet fate of asymptotically non-free gauge theories.

    ↳ hep-thhep-lathep-phPRD(2019)·17 citations
27. 27*

    Cosmological Correlations in Power Law Inflation models

    Amit Kundu🇮🇳 · Prasenjit Paul🇮🇳

    Scalar field with non-minimal coupling to curvature scalar is studied in Robertson-Walker background. The infrared limit of two point function, and, in turn, of the energy-momentum tensor of scalar field have been considered in the power law inflation model. In this limit, within the perfect fluid model, consistent evolution of scale factor following power law inflation gives rise to growing mode solution for negative value of coupling constant. A simplified calculation for density perturbation in power law inflationary models is presented with these mode functions. Salient features of the perturbation spectra has been commented upon.

    ↳ gr-qchep-ph0 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.