Wed·May 13, 2020Wednesday·May 13, 2020

1. 01*

   Flavour symmetries in the SMEFT

   Darius A. Faroughy🇨🇭 · Gino Isidori🇨🇭 · Felix Wilsch🇨🇭 · Kei Yamamoto🇨🇭

   We analyse how $U(3{)}^5$ and $U(2{)}^5$ flavour symmetries act on the Standard Model Effective Field Theory, providing an organising principle to classify the large number of dimension-six operators involving fermion fields. A detailed counting of such operators, at different order in the breaking terms of both these symmetries, is presented. A brief discussion about possible deviations from these two reference cases, and a simple example of the usefulness of this classification scheme for high-$p_T$ analyses at the LHC, are also presented.

   hep-phJHEP(2020)·113 citations
2. 02*

   Predictive Dirac and Majorana Neutrino Mass Textures from $SU(6)$ Grand Unified Theories

   Zackaria Chacko🇺🇸 · P. S. Bhupal Dev🇺🇸 · Rabindra N. Mohapatra🇺🇸 · Anil Thapa🇺🇸

   We present simple and predictive realizations of neutrino masses in theories based on the $SU(6)$ grand unifying group. At the level of the lowest-dimension operators, this class of models predicts a skew-symmetric flavor structure for the Dirac mass term of the neutrinos. In the case that neutrinos are Dirac particles, the lowest-order prediction of this construction is then one massless neutrino and two degenerate massive neutrinos. Higher-dimensional operators suppressed by the Planck scale perturb this spectrum, allowing a good fit to the observed neutrino mass matrix. A firm prediction of this construction is an inverted neutrino mass spectrum with the lightest neutrino hierarchically lighter than the other two, so that the sum of neutrino masses lies close to the lower bound for an inverted hierarchy. In the alternate case that neutrinos are Majorana particles, the mass spectrum can be either normal or inverted. However, the lightest neutrino is once again hierarchically lighter than the other two, so that the sum of neutrino masses is predicted to lie close to the corresponding lower bound for the normal or inverted hierarchy. Near future cosmological measurements will be able to test the predictions of this scenario for the sum of neutrino masses. In the case of Majorana neutrinos that exhibit an inverted hierarchy, future neutrinoless double beta experiments can provide a complementary probe.

   hep-phPRD(2020)·10 citations
3. 03*

   Electrical neutrality and $\beta$-equilibrium conditions in dense quark matter: generation of charged pion condensation by chiral imbalance

   T. G. Khunjua🇬🇪 · K. G. Klimenko🇷🇺 · R. N. Zhokhov🇷🇺

   The phase diagram of dense quark matter with chiral imbalance is considered with the conditions of electric neutrality and $\beta$-equilibrium. It has been shown recently that chiral imbalance can generate charged pion condensation in dense quark matter, so it was interesting to verify that this phenomenon takes place in realistic physical scenarios such as electrically neutral matter in $\beta$-equilibrium, because a window of pion condensation at dense quark matter phase diagram (without chiral imbalance) predicted earlier was closed by the consideration of these conditions at the physical current quark mass. In this paper it has been shown that the charged pion condensation is generated by chiral imbalance in the dense electric neutral quark/baryonic matter in $\beta$-equilibrium, i. e. matter in neutron stars. It has been also demonstrated that pion condensation is inevitable phenomenon in dense quark matter with chiral imbalance if there is non-zero chiral imbalance in two forms, chiral and chiral isospin one. It seems that in this case pion condensation phase can be hardly avoided by any physical constraint on isopin imbalance and that this conclusion can be probably generalized from neutron star matter to the matter produced in heavy ion collisions or in neutron star mergers. The chiral limit and the physical piont (physical pion mass) has been considered and it was shown that the appearance of pion condensation is not much affected by the consideration of non-zero current quark mass.

   hep-phnucl-thEPJC(2020)·13 citations
4. 04*

   A radiatively induced neutrino mass model with hidden local $U(1)$ and LFV processes ${\ell }_i\to {\ell }_j\gamma$, $\mu \to e{Z}^{\prime }$ and $\mu e\to ee$

   Takaaki Nomura🇰🇷 · Hiroshi Okada🇰🇷 · Yuichi Uesaka🇯🇵

   We investigate a model based on hidden $U(1{)}_X$ gauge symmetry in which neutrino mass is induced at one-loop level by effects of interactions among particles in hidden sector and the Standard Model leptons. Neutrino mass generation is also associated with $U(1{)}_X$ breaking scale which is taken to be low to suppress neutrino mass. Then we formulate neutrino mass matrix, lepton flavor violating processes and muon $g-2$ which are induced via interactions among Standard Model leptons and particles in $U(1{)}_X$ hidden sector that can be sizable in our scenario. Carrying our numerical analysis, we show expected ratios for these processes when generated neutrino mass matrix can fit the neutrino data.

   hep-phJHEP(2021)·11 citations
5. 05*

   A massive composite fermion from the three electron-like leptons in the bound state in the continuum

   A.I. Agafonov🇷🇺

   In the bound state in continuum (BIC) the mass of a composite particle is greater than the total mass of its constituent particles. The BIC states that are stable due to confinement mechanisms, have been found in various fields but particle physics has evolved without analyzing these states. The work's idea is to apply the BIC phenomenon to some elementary particles. The study focuses on a composite fermion of the three light leptons, $(e^{-}{e}^{+}{e}^{\pm }{)}_{BIC}$. In the present theory the free electron and free positron is treated as different particles, each being characterized by the complete set of the Dirac plane waves. Using the Bethe-Salpeter equation, the wave function of the fermion with the mass of 207 electron masses was found numerically. The results obtained predict the particle radius equal to 65.9 Fm. The representation of muons as the composite fermions formed by the three electron-like leptons in the BIC states, is analyzed.

   hep-ph0 citations
6. 06*

   Inflationary cosmology- A new approach using Non-linear electrodynamics

   Payel Sarkar🇮🇳 · Prasanta Kumar Das🇮🇳 · Gauranga Charan Samanta🇮🇳

   We explore a new kind of field of nonlinear electrodynamics(NLED) which acts as a source of gravity and can accelerate the universe during the inflationary era. We propose a new type of NLED lagrangian which is charecterized by two paremetrs $\alpha$ and $\beta$. We investigate the classical stability and causality aspects of this model by demanding that the speed ($C_s=\frac{dP}{d\rho }$) of the sound wave $C_s^2>0$ and $C_s\le 1$ and find that $0<C_s^2<1$ corresponds to $0.25\le \alpha \le 0.4$ and $0.6\le \beta B^2\le 1$. A study of the deceleration parameter($q=\frac{1}{2}(1+3\omega )$, $\omega =P/\rho$ being the equation of state parameter) suggests that the value $q<0$ (i.e. $\omega <-1/3$ and $\ddot{a}(t)>0$ ( the accelerating universe)) requires $\beta B^2\ge 0.13$. During inflation, the energy density ${\rho }_B$ is found to be maximum and is given by ${\rho }_B^{max}=0.65/\beta$ corresponding to $\alpha =0.3$. The magnetic field necessary to trigger the inflation, is found to be $B(=B_{max})\simeq \sqrt{\frac{0.4{\rho }_B^{max}}{0.65}}=4\times 10^{51}\mathrm{Gauss}$, where ${\rho }_B^{max}(=10^{64}{\mathrm{GeV}}^4$) is the energy density of the universe during inflation. The model also predict the e-fold number $N=71$, which agrees with the experimental result.

   hep-phastro-ph.COPhys.Scripta(2021)·9 citations
7. 07*

   A Framework for Hadronic Rescattering in pp Collisions

   Torbjörn Sjöstrand🇸🇪 · Marius Utheim🇸🇪

   In this article, a framework for hadronic rescattering in the general-purpose Pythia event generator is introduced. The starting point is the recently presented space-time picture of the hadronization process. It is now extended with a tracing of the subsequent motion of the primary hadrons, including both subsequent scattering processes among them and decays of them. The major new component is cross-section parameterizations for a range of possible hadron-hadron combinations, applicable from threshold energies upwards. The production dynamics in these collisions has also been extended to cope with different kinds of low-energy processes. The properties of the model are studied, and some first comparisons with LHC pp data are presented. Whereas it turns out that approximately half of all final particles participated in rescatterings, the net effects in pp events are still rather limited, and only striking in a few distributions. The new code opens up for several future studies, however, such as effects in pA and AA collisions.

   hep-phEPJC(2020)·42 citations
8. 08*

   Nuclear modification factors for jet fragmentation

   P. Caucal🇫🇷 · E. Iancu🇫🇷 · A. H. Mueller🇺🇸 · G. Soyez🇫🇷

   Using a recently-developed perturbative-QCD approach for jet evolution in a dense quark-gluon plasma, we study the nuclear modification factor for the jet fragmentation function. The qualitative behaviour that we find is in agreement with the respective experimental observations in Pb+Pb collisions at the LHC: a pronounced nuclear enhancement at both ends of the spectrum. Our Monte Carlo simulations are supplemented with analytic estimates which clarify the physical interpretation of the results. The main source of theoretical uncertainty is the sensitivity of our calculations to a low-momentum cutoff which mimics confinement. To reduce this sensitivity, we propose a new observable, which describes the jet fragmentation into subjets and is infrared-and-collinear safe by construction. We present Monte Carlo predictions for the associated nuclear modification factor together with their physical interpretation.

   hep-phnucl-thJHEP(2020)·38 citations
9. 09*

   Matching and running sensitivity in non-renormalizable inflationary models

   Jacopo Fumagalli🇫🇷 · Marieke Postma🇳🇱 · Melvin van den Bout🇳🇱

   Most of the inflationary models that are in agreement with the Planck data rely on the presence of non-renormalizable operators. If the connection to low energy particle physics is made, the renormalization group (RG) introduces a sensitivity to ultraviolet (UV) physics that can be crucial in determining the inflationary predictions. We analyse this effect for the Standard Model (SM) augmented with non-minimal derivative couplings to gravity. Our set-up reduces to the SM for small values of the Higgs field, and allows for inflation in the opposite large field regime. The one-loop beta functions in the inflationary region are calculated using a covariant approach that properly accounts for the non-trivial structure of the field space manifold. We run the SM parameters from the electroweak to the inflationary scale, matching the couplings of the different effective field theories at the boundary between the two regimes, where we also include threshold corrections that parametrize effects from UV physics. We then compute the spectral index and tensor-to-scalar ratio and find that RG flow corrections can be determinant: a scenario that is ruled out at tree level can be resurrected and vice versa.

   hep-phastro-ph.COhep-thJHEP(2020)·19 citations
10. 10*

    CPT and CP, an entangled couple

    Gabriela Barenboim🇪🇸 · Christoph A. Ternes🇪🇸 · Mariam Tórtola🇪🇸

    Even though it is undoubtedly very appealing to interpret the latest T2K results as evidence of CP violation, this claim assumes CPT conservation in the neutrino sector to an extent that has not been tested yet. As we will show, T2K results are not robust against a CPT-violating explanation. On the contrary, a CPT-violating CP-conserving scenario is in perfect agreement with current neutrino oscillation data. Therefore, to elucidate whether T2K results imply CP or CPT violation is of utter importance. We show that, even after combining with data from NO$\nu$A and from reactor experiments, no claims about CP violation can be made. Finally, we update the bounds on CPT violation in the neutrino sector.

    hep-phhep-exJHEP(2020)·26 citations
11. 11*

    ${\epsilon }^{\prime }/\epsilon$ in the Standard Model at the Dawn of the 2020s

    Jason Aebischer🇺🇸 · Christoph Bobeth🇩🇪 · Andrzej J. Buras🇩🇪

    We reanalyse the ratio ${\epsilon }^{\prime }/\epsilon$ in the Standard Model (SM) using most recent hadronic matrix elements from the RBC-UKQCD collaboration in combination with most important NNLO QCD corrections to electroweak penguin contributions and the isospin-breaking corrections. We illustrate the importance of the latter by using their latest estimate from chiral perturbation theory (ChPT) based on the $octet$ approximation for lowest-lying mesons and a very recent estimate in the $nonet$ scheme that takes into account the contribution of ${\eta }_0$. We find $({\epsilon }^{\prime }/\epsilon {)}_{\text{SM}}^{(8)}=(17.4\pm 6.1)\times 10^{-4}$ and $({\epsilon }^{\prime }/\epsilon {)}_{\text{SM}}^{(9)}=(13.9\pm 5.2)\times 10^{-4}$, respectively. Despite a very good agreement with the measured value $({\epsilon }^{\prime }/\epsilon {)}_{\text{exp}}=(16.6\pm 2.3)\times 10^{-4}$, the large error in $({\epsilon }^{\prime }/\epsilon {)}_{\text{SM}}$ still leaves room for significant new physics (BSM) contributions to this ratio. We update the 2018 master formula for $({\epsilon }^{\prime }/\epsilon {)}_{\text{BSM}}$ valid in any extension beyond the SM without additional light degrees of freedom. We provide new values of the penguin parameters $B_6^{(1/2)}(\mu )$ and $B_8^{(3/2)}(\mu )$ at the $\mu$-scales used by the RBC-UKQCD collaboration and at lower scales $\mathcal{O}(1\text{GeV})$ used by ChPT and DQCD. We present semi-analytic formulae for $({\epsilon }^{\prime }/\epsilon {)}_{\text{SM}}$ in terms of these parameters and ${\hat{\Omega }}_{\text{eff}}$ that summarizes isospin-breaking corrections to this ratio. We stress the importance of lattice calculations of the $\mathcal{O}({\alpha }_{\text{em}})$ contributions to the hadronic matrix elements necessary for the removal of renormalization scheme dependence at $\mathcal{O}({\alpha }_{\text{em}})$ in the present analyses of ${\epsilon }^{\prime }/\epsilon$.

    hep-phhep-exhep-latEPJC(2020)·42 citations
12. 12*

    Origin of cosmological temperature

    Daniel Friedan🇺🇸

    A classical solution of the Standard Model + General Relativity is given by an elliptic function whose periodicity in imaginary time is the origin of cosmological temperature. Nothing beyond the Standard Model is assumed. The solution is a $\mathrm{Spin}(4)$-symmetric universe expanding prior to the electroweak transition. A rapidly oscillating $\mathrm{SU}(2)$ gauge field holds the Higgs field to $0$ with strength inversely proportional to the scale factor $a$. When $a$ reaches $a_{\mathrm{EW}}$ the solution becomes unstable and the electoweak transition begins. $a_{\mathrm{EW}}$ is the only free parameter in the solution. The temperature at $a_{\mathrm{EW}}$ is $m_H/(6\pi {)}^{1/2}=28.8\text{GeV}=3.34\times 10^{14}\text{K}$ whatever the value of $a_{\mathrm{EW}}$.

    ↳ astro-ph.COgr-qchep-phhep-th9 citations
13. 13*

    Effective theories for a nonrelativistic field in an expanding universe: Induced self-interaction, pressure, sound speed, and viscosity

    Borna Salehian🇮🇷 · Mohammad Hossein Namjoo🇮🇷 · David I. Kaiser🇺🇸

    A massive, nonrelativistic scalar field in an expanding spacetime is usually approximated by a pressureless perfect fluid, which leads to the standard conclusion that such a field can play the role of cold dark matter. In this paper, we systematically study these approximations, incorporating subleading corrections. We provide two equivalent effective descriptions of the system, each of which offers its own advantages and insights: (i) A nonrelativistic effective field theory (EFT) with which we show that the relativistic corrections induce an effective self-interaction for the nonrelativistic field. As a byproduct, our EFT also allows one to construct the exact solution, including oscillatory behavior, which is often difficult to achieve from the exact equations. (ii) An effective (imperfect) fluid description, with which we demonstrate that, for a perturbed Friedmann-Lemaître-Robertson-Walker (FLRW) universe: (a) The pressure is small but nonzero (and positive), even for a free theory with no tree-level self-interactions. (b) The sound speed of small fluctuations is also nonzero (and positive), reproducing already known leading-order results, correcting a subdominant term, and identifying a new contribution that had been omitted in previous analyses. (c) The fluctuations experience a negative effective bulk viscosity. The positive sound speed and the negative bulk viscosity act in favor of and against the growth of overdensities, respectively. The net effect may be considered a smoking gun for ultra-light dark matter.

    ↳ astro-ph.COhep-phhep-thJHEP(2020)·27 citations
14. 14*

    Abelian Higgs model in power-law inflation: the propagators in the unitary gauge

    Dražen Glavan🇧🇪 · Anja Marunović🇳🇱 · Tomislav Prokopec🇳🇱 · Zahra Zahraee🇨🇦

    We consider the Abelian Higgs model in the broken phase as a spectator in cosmological spaces of general $D$ space-time dimensions, and allow for the condensate to be time-dependent. We fix the unitary gauge using Dirac's formalism for constrained systems, and then quantize the gauge-fixed system. Vector and scalar perturbations develop time-dependent masses. We work out their propagators assuming the cosmological background is that of power-law inflation, characterized by a constant principal slow-roll parameter, and that the scalar condensate is in the attractor regime, scaling as the Hubble rate. Our propagators correctly reduce to known results in the Minkowski and de Sitter space limits. We use the vector propagator to compute the equal-time correlators of electric and magnetic fields and find that at super-Hubble separations the former is enhanced, while the latter is suppressed compared to the vacuum fluctuations of the massless vector field. These correlators satisfy the hierarchy governed by Faraday's law.

    ↳ gr-qcastro-ph.COhep-phhep-thJHEP(2020)·8 citations
15. 15*

    21cm forest probes on the axion dark matter in the post-inflationary Peccei-Quinn symmetry breaking scenarios

    Hayato Shimabukuro🇨🇳 · Kiyotomo Ichiki🇯🇵 · Kenji Kadota🇰🇷

    We study the future prospects of the 21cm forest observations on the axion-like dark matter when the spontaneous breaking of the global Peccei-Quinn (PQ) symmetry occurs after the inflation. The large isocurvature perturbations of order unity sourced from axion-like particles can result in the enhancement of minihalo formation, and the subsequent hierarchical structure formation can affect the minihalo abundance whose masses can exceed $\mathcal{O}(10^4)M_{\odot }$ relevant for the 21cm forest observations. We show that the 21cm forest observations are capable of probing the axion-like particle mass in the range $10^{-18}\lesssim m_a\lesssim 10^{-12}$ eV for the temperature independent axion mass. For the temperature dependent axion mass, the zero temperature axion mass scale for which the 21cm forest measurements can be affected is extended further to as big as of order $10^{-6}$ eV.

    ↳ astro-ph.COhep-phhep-thPRD(2020)·21 citations
16. 16*

    A Novel Algorithm for Nested Summation and Hypergeometric Expansions

    Andrew J. McLeod🇩🇰 · Henrik Munch🇩🇰 · Georgios Papathanasiou🇩🇪 · Matt von Hippel🇩🇰

    We consider a class of sums over products of Z-sums whose arguments differ by a symbolic integer. Such sums appear, for instance, in the expansion of Gauss hypergeometric functions around integer indices that depend on a symbolic parameter. We present a telescopic algorithm for efficiently converting these sums into generalized polylogarithms, Z-sums, and cyclotomic harmonic sums for generic values of this parameter. This algorithm is illustrated by computing the double pentaladder integrals through ten loops, and a family of massive self-energy diagrams through $O({ϵ}^6)$ in dimensional regularization. We also outline the general telescopic strategy of this algorithm, which we anticipate can be applied to other classes of sums.

    ↳ hep-thhep-phJHEP(2020)·10 citations
17. 17*

    Primordial Black Holes Confront LIGO/Virgo data: Current situation

    V. De Luca🇨🇭 · G. Franciolini🇨🇭 · P. Pani🇮🇹 · A. Riotto🇨🇭

    The LIGO and Virgo Interferometers have so far provided 11 gravitational-wave (GW) observations of black-hole binaries. Similar detections are bound to become very frequent in the near future. With the current and upcoming wealth of data, it is possible to confront specific formation models with observations. We investigate here whether current data are compatible with the hypothesis that LIGO/Virgo black holes are of primordial origin. We compute in detail the mass and spin distributions of primordial black holes (PBHs), their merger rates, the stochastic background of unresolved coalescences, and confront them with current data from the first two observational runs, also including the recently discovered GW190412. We compute the best-fit values for the parameters of the PBH mass distribution at formation that are compatible with current GW data. In all cases, the maximum fraction of PBHs in dark matter is constrained by these observations to be $f_{\text{PBH}}\approx \mathrm{few}\times 10^{-3}$. We discuss the predictions of the PBH scenario that can be directly tested as new data become available. In the most likely formation scenarios where PBHs are born with negligible spin, the fact that at least one of the components of GW190412 is moderately spinning is incompatible with a primordial origin for this event, unless accretion or hierarchical mergers are significant. In the absence of accretion, current non-GW constraints already exclude that LIGO/Virgo events are all of primordial origin, whereas in the presence of accretion the GW bounds on the PBH abundance are the most stringent ones in the relevant mass range. A strong phase of accretion during the cosmic history would favour mass ratios close to unity, and a redshift-dependent correlation between high masses, high spins and nearly-equal mass binaries, with the secondary component spinning faster than the primary.

    ↳ astro-ph.COgr-qchep-phJCAP(2020)·218 citations
18. 18*

    Measurement of the Born Cross Sections for $e^{+}{e}^{-}\to D_s^{+}{D}_{s1}(2460{)}^{-}+c.c.$ and $e^{+}{e}^{-}\to D_s^{\ast +}{D}_{s1}(2460{)}^{-}+c.c.$

    BESIII Collaboration: M. Ablikim · M. N. Achasov · P. Adlarson · S. Ahmed · M. Albrecht · A. Amoroso · Q. An · Anita · Y. Bai · O. Bakina · R. Baldini Ferroli · I. Balossino and 479 other authors

    The processes $e^{+}{e}^{-}\to D_s^{+}{D}_{s1}(2460{)}^{-}+c.c.$ and $e^{+}{e}^{-}\to D_s^{\ast +}{D}_{s1}(2460{)}^{-}+c.c.$ are studied for the first time using data samples collected with the BESIII detector at the BEPCII collider. The Born cross sections of $e^{+}{e}^{-}\to D_s^{+}{D}_{s1}(2460{)}^{-}+c.c.$ at nine center-of-mass energies between 4.467\,GeV and 4.600\,GeV and those of $e^{+}{e}^{-}\to D_s^{\ast +}{D}_{s1}(2460{)}^{-}+c.c.$ at $\sqrt{s}=$ 4.590\,GeV and 4.600\,GeV are measured. No obvious charmonium or charmonium-like structure is seen in the measured cross sections.

    ↳ hep-exhep-phPRD(2020)·8 citations
19. 19*

    Experimental review of the ${\rm Y}(1S,2S,3S)$ physics at $e^{+}{e}^{-}$ colliders and the LHC

    Sen Jia🇨🇳 · Xingyu Zhou🇨🇳 · Chengping Shen🇨🇳

    The three lowest-lying ${\rm Y}$ states, i.e. ${\rm Y}(1S)$, ${\rm Y}(2S)$, and ${\rm Y}(3S)$, composed of $b\bar{b}$ pairs and below the $B\bar{B}$ threshold, provide a good platform for the researches of hadronic physics and physics beyond the Standard Model. They can be produced directly in $e^{+}{e}^{-}$ colliding experiments, such as CLEO, Babar, and Belle, with low continuum backgrounds. In these experiments, many measurements of the exclusive ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays into light hadrons, which shed light on the "80\% rule" for the Okubo-Zweig-Iizuka suppressed decays in the bottomonium sector, were carried out. Meanwhile, many studies of the charmonium and bottomonium productions in ${\rm Y}(1S,2S,3S)$ decays were performed, to distinguish different Quantum Chromodynamics (QCD) models. Besides, exotic states and new physics were also extensively explored in ${\rm Y}(1S,2S,3S)$ decays at CLEO, BaBar, and Belle. The ${\rm Y}(1S,2S,3S)$ states can also be produced in $pp$ collisions and in collisions involving heavy ions. The precision measurements of their cross sections and polarizations at the large hadron collider (LHC), especially in the CMS, ATLAS, and LHCb experiments, help to understand ${\rm Y}$ production mechanisms in $pp$ collisions. The observation of the sequential ${\rm Y}$ suppression in heavy ion collisions at CMS is of great importance for verifying the quark-gluon plasma predicted by QCD. In this article, we review the experimental results on ${\rm Y}(1S,2S,3S)$ at $e^{+}{e}^{-}$ colliders and the LHC, and summarize their prospects at Belle II and the LHC.

    ↳ hep-exhep-phFront.Phys.(Beijing)(2020)·7 citations
20. 20*

    Comment on "Multiscatter stellar capture of dark matter"

    Cosmin Ilie🇺🇸 · Jacob Pilawa🇺🇸 · Saiyang Zhang🇺🇸

    Bramante, Delgado, and Martin [Phys. Rev. D96, 063002(2017)., hereafter BDM17] extended the analytical formalism of dark matter (DM) capture in a very important way, which allows, in principle, the use of compact astrophysical objects, such as neutron stars (NS), as dark matter detectors. In this comment, we point out the existence of a region in the dark matter neutron scattering cross section $({\sigma }_{nX})$ vs. dark matter mass $(m_X)$ where the constraining power of this method is lost. This corresponds to a maximal temperature ($T_{crit}$) the NS has to have, in order to serve as a dark matter detector. In addition, we point out several typos and errors in BDM17 that do not affect drastically their conclusions. Moreover, we provide semi-analytical approximations for the total capture rates of dark matter particle of arbitrary mass for various limiting regimes. Those analytical approximations are used to validate our numerical results.

    ↳ astro-ph.COastro-ph.HEastro-ph.SRhep-phPRD(2020)·57 citations
21. 21*

    On the derivatives of feed-forward neural networks

    Rabah Abdul Khalek🇳🇱 · Valerio Bertone🇫🇷

    In this paper we present a C++ implementation of the analytic derivative of a feed-forward neural network with respect to its free parameters for an arbitrary architecture, known as back-propagation. We dubbed this code NNAD (Neural Network Analytic Derivatives) and interfaced it with the widely-used ceres-solver minimiser to fit neural networks to pseudodata in two different least-squares problems. The first is a direct fit of Legendre polynomials. The second is a somewhat more involved minimisation problem where the function to be fitted takes part in an integral. Finally, using a consistent framework, we assess the efficiency of our analytic derivative formula as compared to numerical and automatic differentiation as provided by ceres-solver. We thus demonstrate the advantage of using NNAD in problems involving both deep or shallow neural networks.

    ↳ physics.comp-phhep-ph11 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.