Wed·Jul 31, 2019Wednesday·July 31, 2019

1. 01*

   Enumerating the operators of an effective field theory

   Renato M. Fonseca🇨🇿

   Until recently little was known about the high-dimensional operators of the standard model effective field theory (SMEFT). However, in the past few years the number of these operators has been counted up to mass dimension 15 using techniques involving the Hilbert series. In this work I will show how to perform the same counting with a different method. This alternative approach makes it possible to cross-check results (it confirms the SMEFT numbers), but it also provides some more information on the operators beyond just counting their number. The considerations made here apply equally well to any other model besides SMEFT and, with this purpose in mind, they were implemented in a computer code.

   hep-phhep-thPRD(2020)·83 citations
2. 02*

   Precise predictions for single-top production: the impact of EW corrections and QCD shower on the t-channel signature

   Rikkert Frederix🇸🇪 · Davide Pagani🇩🇪 · Ioannis Tsinikos🇩🇪

   In this work we calculate and provide precise predictions for the signature that is typically exploited at the LHC for the measurement of t-channel single-top production: 1 lepton, 1 light jet, 1 b-jet, missing-ET and no additional jets or leptons. We apply the cuts that define the fiducial region and we take into account all the contributions to this signature; not only those from resonant t-channel single-top production. On the one hand, we calculate the complete-NLO corrections, i.e., all NLO effects of QCD and EW origin. On the other hand, we study in detail the impact of a QCD parton shower for the fiducial region we consider. We provide predictions in different approximations at the inclusive level and for several differential distributions. Our study demonstrates the relevance of both EW corrections and shower effects for obtaining precise and reliable theoretical predictions for the single-top-production fiducial region.

   hep-phJHEP(2019)·21 citations
3. 03*

   Stability of Gluonic Systems with Multiple Soft Interactions

   Rahul Kumar Thakur🇮🇳 · Bhupendra Nath Tiwari🇮🇹 · Rahul Nigam🇮🇳

   In this paper, we investigate the stability properties of soft gluons in SIBYLL 2.1 with reference to its original version 1.7 that corresponds to hadronic hard interactions. In order to investigate the stability structures, we classify the regions of the gluon density fluctuations in its double leading logarithmic approximation and its equivalent description as the fractional power law. In the parameter space of initial transverse momentum $Q$ and QCD renormalization scale $L$ that correspond to extensive air showers of cosmic rays, we have categorized the surface of parameters over which the proton is stable. We further discuss the nature of local and global correlations and stability properties where the concerning statistical basis yields a stable system or undergoes a geometric phase transition. Finally, we give a phenomenological understanding towards the stability of soft interactions, Pomeron particle productions in minijet model, string fragmentation and verify our result corresponding to the experiments - CDF, P238, UAS, GEUS and UA4 collaborations.

   hep-phastro-ph.HEJ.Astrophys.Astron.(2019)·1 citation
4. 04*

   Neutrino counting experiments and non-unitarity from LEP and future experiments

   F. J. Escrihuela🇪🇸 · L. J. Flores🇲🇽 · O. G. Miranda🇲🇽

   Non-unitarity of the neutrino mixing matrix is expected in many scenarios with physics beyond the Standard Model. Motivated by the search for deviations from unitary, we study two neutrino counting observables: the neutrino-antineutrino gamma process and the invisible $Z$ boson decay into neutrinos. We report on new constraints for non-unitarity coming from the first of this observables. We study the potential constraints that future collider experiments will give from the invisible decay of the Z boson, that will be measured with improved precision.

   hep-phPLB(2020)·16 citations
5. 05*

   Triangle singularities in $J/\psi \to \eta {\pi }^0\varphi$ and ${\pi }^0{\pi }^0\varphi$

   Hao-Jie Jing🇨🇳 · Shuntaro Sakai🇨🇳 · Feng-Kun Guo🇨🇳 · Bing-Song Zou🇨🇳

   The BESIII Collaboration recently reported the observation of the $a_0(980{)}^0-f_0(980)$ mixing in the isospin breaking decay $J/\psi \to \eta {\pi }^0\varphi$. In the Dalitz plot for that decay with the $\eta$ reconstructed from two photons, there is a band around $1.4$~GeV on the ${\pi }^0\varphi$ distribution. In general, this peak can be due to a resonance or a kinematic effect. In this paper, we study the effects of a set of $K^{\ast }K\bar{K}$ triangle diagrams, and show that due to triangle singularities such diagrams can lead to a peak around 1.4~GeV in the ${\pi }^0\varphi$ invariant mass distribution. The Dalitz plot induced by such a mechanism has a feature consistent with the BESIII observation, namely events along the band accumulate at both ends close to the Dalitz plot boundary. The effect of the same mechanism on the $J/\psi \to {\pi }^0{\pi }^0\varphi$ and $J/\psi \to \eta {\pi }^0{K}^{+}{K}^{-}$ decays are also investigated. We suggest to take more data for the $J/\psi \to \eta {\pi }^0\varphi \to \eta {\pi }^0{K}^{+}{K}^{-}$ and check whether the structure around $1.4$~GeV persists for the $K^{+}{K}^{-}$ invariant mass away from the $\varphi$ mass region. This is crucial for understanding whether the band is due to triangle singularities or due to a resonance. Were it the latter, the band should remain while it would not if it is due to the former.

   hep-phPRD(2019)·31 citations
6. 06*

   A phenomenological investigation of the integral and the differential versions of the Kimber-Martin$-Ryskin$unintegrated$ parton distribution functions using two different constraints and the MMHT2014 PDF

   N. Olanj🇮🇷 · M. Modarres🇮🇷

   We previously investigated the compatibility of the $Kimber$-$Martin$-$Ryskin$ ($KMR$) $unintegrated$ parton distribution functions ($UPDF$) with the experimental data on the proton (longitudinal) structure functions ($PSF$ ($PLSF$)). Recently $Golec-Biernat$ and $Stasto$ ($GBS$) demonstrated that the differential version of $KMR$ prescription and the implementations of angular (strong) ordering ($AOC$ ($SOC$)) constraints, cause the negative-discontinuous $UPDF$ with the ordinary parton distribution functions ($PDF$) as the input, which leads to a sizable effect on the calculation of $PSF$. In the present work, we use the new $MMHT2014$-$LO$-$PDF$ as the input and focus on the $UPDF$ behaviors as was raised by $GBS$. The resulting $PSF$ and $PLSF$ are compared with the $MSTW2008$-$LO$-$PDF$ and $MRST99$-$PDF$ and the 2014 data given by the $ZEUS$ and $H1$ collaborations. The calculated $PSF$ and $PLSF$ based on the integral prescription of the $KMR$-$UPDF$ with the $AOC$ and the ordinary $PDF$ as the input are reasonably consistent with the experimental data. Therefore, they are approximately independent to the $PDF$ (no need to impose cutoff on the $PDF$). At very small $x$ regions because of the excess of gluons in the $MMHT2014$-$LO$-$PDF$ and $MSTW2008$-$LO$-$PDF$, an increase in $PSF$ and $PLSF$ is achieved. Finally, according to the $GBS$ report the differential version by using the cutoff independent $PDF$ produces results far from the experimental data.

   hep-phEPJC(2019)·9 citations
7. 07*

   A 96 GeV scalar tagged to dark matter models

   Anirban Kundu🇮🇳 · Suvam Maharana🇮🇳 · Poulami Mondal🇮🇳

   Recently, the CMS Collaboration observed the hint of a resonance decaying to two photons at about 96 GeV with a local significance of $2.8\sigma$. While it is too early to say whether this will stand the test of time, such a resonance can easily be accommodated in many extensions of the Standard Model (SM). The more challenging part is to tune such an extension so that the required number of diphoton events is reproduced. Assuming that the new resonance is a scalar, we propose that the signal may come either from an ultraviolet complete model with vectorial quarks, or a model involving gluon-scalar and photon-scalar effective operators. We then incorporate this portal to several extensions of the SM that include one or more cold dark matter candidates, and try to investigate how the existence of such a scalar resonance affects the parameter space of such models. As expected, we find that with such a scalar, the parameter space gets more constrained and hence, more tractable. We show how significant constraints can be placed on the parameter space, not only from direct dark matter searches or LHC data but also from theoretical considerations like scattering unitarity or stability of the potential, and discuss some novel features of the allowed parameter space.

   hep-phastro-ph.CONPB(2020)·28 citations
8. 08*

   Muon pair production via photon-induced scattering at the CLIC in models with extra dimensions

   S.C. Inan🇹🇷 · A.V. Kisselev🇹🇷

   The photon-induced dimuon production $e^{+}{e}^{-}\to e^{+}\gamma \gamma e^{-}\to e^{+}{\mu }^{+}{\mu }^{-}{e}^{-}$ at the CLIC is studied in the framework of three models with extra dimensions. The electron beam energies 750 GeV and 1500 GeV are considered. The total cross sections are calculated depending on the minimal transverse momenta of the final muons. The sensitivity bounds on the parameters of the models are obtained as functions of the CLIC integrated luminosity.

   hep-phhep-exNPB(2020)·4 citations
9. 09*

   Absorption cross section in an intense plane wave background

   Anton Ilderton🇬🇧 · Ben King🇬🇧 · Alexander John Macleod🇬🇧

   We consider the absorption of probe photons by electrons in the presence of an intense, pulsed, background field. Our analysis reveals an interplay between regularisation and gauge invariance which distinguishes absorption from its crossing-symmetric processes, as well as a physical interpretation of absorption in terms of degenerate processes in the weak field limit. In the strong field limit we develop a locally constant field approximation (LCFA) for absorption which also exhibits new features. We benchmark the LCFA against exact analytical calculations and explore its regime of validity. Pulse shape effects are also investigated, as well as infra-red and collinear limits of the absorption process.

   hep-phphysics.plasm-phPRD(2019)·20 citations
10. 10*

    Generalized phenomenological models of dark energy

    Prasenjit Paul🇮🇳 · Rikpratik Sengupta🇮🇳

    It was first observed at the end of the last century that the universe is presently accelerating. Ever since, there have been several attempts to explain this observation theoretically. There are two possible approaches. The more conventional one is to modify the matter part of the Einstein Field Equations and the second one is to modify the geometry part. We shall consider two phenomenological models based on the former, more conventional approach within the context of General Relativity. The phenomenological models in this paper consider a $\Lambda$ term as a function of $\frac{\ddot{a}}{a}$ and $\rho$ where $a$ and $\rho$ are the scale factor and matter-energy density respectively. Constraining the free parameters of the models with latest observational data gives satisfactory values of parameters as considered by us initially. Without any field-theoretic interpretation, we explain the recent observations with a dynamical cosmological constant.

    hep-phgr-qcAdv.High Energy Phys.(2020)·4 citations
11. 11*

    Dipole evolution: perspectives for collectivity and ${\gamma }^{\ast }$A collisions

    Christian Bierlich🇸🇪 · Christine O. Rasmussen🇸🇪

    The transverse, spatial structure of protons is an area revealing fundamental properties of matter, and provides key input for deeper understanding of emerging collective phenomena in high energy collisions of protons, as well as collisions of heavy ions. In this paper eccentricities and eccentricity fluctuations are predicted using the dipole formulation of BFKL evolution. Furthermore, first steps are taken towards generation of fully exclusive final states of ${\gamma }^{\ast }$A collisions, by assessing the importance of colour fluctuations in the initial state. Such steps are crucial for the preparation of event generators for a future electron-ion collider. Due to the connection between an impact parameter picture of the proton structure, and cross sections of ep and pp collisions, the model parameters can be fully determined by fits to such quantities, leaving results as real predictions of the model.

    hep-phnucl-thJHEP(2019)·22 citations
12. 12*

    Single-jet inclusive rates with exact color at $\mathcal{O}({\alpha }_s^4)$

    Michal Czakon🇩🇪 · Andreas van Hameren🇵🇱 · Alexander Mitov🇬🇧 · Rene Poncelet🇬🇧

    Next-to-next-to-leading order QCD predictions for single-, double- and even triple-differential distributions of jet events in proton-proton collisions have recently been obtained using the NNLOjet framework based on antenna subtraction. These results are an important input for Parton Distribution Function fits to hadron-collider data. While these calculations include all of the partonic channels occurring at this order of the perturbative expansion, they are based on the leading-color approximation in the case of channels involving quarks and are only exact in color in the pure-gluon channel. In the present publication, we verify that the sub-leading color effects in the single-jet inclusive double-differential cross sections are indeed negligible as far as phenomenological applications are concerned. This is the first independent and complete calculation for this observable. We also take the opportunity to discuss the necessary modifications of the sector-improved residue subtraction scheme that made this work possible.

    hep-phhep-exJHEP(2019)·126 citations
13. 13*

    On Lepton Number Violation in Heavy Neutrino Decays at Colliders

    Marco Drewes🇧🇪 · Juraj Klarić🇨🇭 · Philipp Klose🇧🇪

    We study the perspective to observe lepton number violating signatures from heavy Majorana neutrino decays at colliders in view of the requirement to explain the light neutrino masses via the seesaw mechanism. In the minimal model with only two heavy neutrinos and in the $\nu$MSM one can identify three distinct regions in the mass-mixing plane. For Majorana masses above the electroweak scale the branching ratio for lepton number violating processes at the LHC is generically suppressed. For masses well below the electroweak scale that are probed in displaced vertex searches or at fixed target experiments lepton number violation is the rule and can only be avoided at the cost of fine tuning. In between there is a mass regime where both possibilities coexist. In models with more than two heavy neutrinos the larger parameter space allows for more freedom, but our results remain qualitatively correct unless there is a mass degeneracy amongst more than two of the heavy neutrinos.

    hep-phhep-exJHEP(2019)·83 citations
14. 14*

    OpenLoops 2

    Federico Buccioni🇨🇭 · Jean-Nicolas Lang🇨🇭 · Jonas M. Lindert🇬🇧 · Philipp Maierhöfer🇩🇪 · Stefano Pozzorini🇨🇭 · Hantian Zhang🇨🇭 · Max F. Zoller🇨🇭

    We present the new version of OpenLoops, an automated generator of tree and one-loop scattering amplitudes based on the open-loop recursion. One main novelty of OpenLoops 2 is the extension of the original algorithm from NLO QCD to the full Standard Model, including electroweak (EW) corrections from gauge, Higgs and Yukawa interactions. In this context, among several new features, we discuss the systematic bookkeeping of QCD-EW interferences, a flexible implementation of the complex-mass scheme for processes with on-shell and off-shell unstable particles, a special treatment of on-shell and off-shell external photons, and efficient scale variations. The other main novelty is the implementation of the recently proposed on-the-fly reduction algorithm, which supersedes the usage of external reduction libraries for the calculation of tree-loop interferences. This new algorithm is equipped with an automated system that avoids Gram-determinant instabilities through analytic methods in combination with a new hybrid-precision approach based on a highly targeted usage of quadruple precision with minimal CPU overhead. The resulting significant speed and stability improvements are especially relevant for challenging NLO multi-leg calculations and for NNLO applications.

    hep-phhep-exEPJC(2019)·807 citations
15. 15*

    Gravitational Wave Signals of Pseudo-Goldstone Dark Matter in the ${\mathbb{Z}}_3$ Complex Singlet Model

    Kristjan Kannike🇪🇪 · Kaius Loos🇪🇪 · Martti Raidal🇪🇪

    We study pseudo-Goldstone dark matter in the ${\mathbb{Z}}_3$ complex scalar singlet model. Because the direct detection spin-independent cross section is suppressed, such dark matter is allowed in a large mass range. Unlike in the original model stabilized by a parity, due to the cubic coupling of the singlet the ${\mathbb{Z}}_3$ model can accommodate first-order phase transitions that give rise to a stochastic gravitational wave signal potentially observable in future space-based detectors.

    hep-phPRD(2020)·52 citations
16. 16*

    $a_1$ meson-baryon coupling constants in the framework of soft-wall and hard-wall AdS/QCD models

    Narmin Huseynova🇦🇿 · Shahin Mamedov🇦🇿

    We calculate the $a_1$ meson-nucleon coupling constant in the framework of soft-wall and hard-wall AdS/QCD models. In the bulk of AdS space were written bulk interaction Lagrangians for a minimal gauge coupling, a magnetic gauge coupling and a triple coupling. To use AdS/CFT correspondence and these bulk interaction Lagrangians we calculate the $a_1$ axial-vector meson-nucleon coupling constant in the boundary of AdS space within both models. We observe that the numerical values for the $g_{a_{1}NN}$ coupling constant in the framework of both models are more close to the experimental value than results in other works. We also calculate the $g_{a_1\Delta \Delta }$ axial-vector meson-$\Delta$-baryon coupling constant in the framework of hard-wall AdS/QCD model.

    hep-phhep-thInt.J.Mod.Phys.A(2020)·9 citations
17. 17*

    A radiative seesaw model in modular $A_4$ symmetry

    Hiroshi Okada🇰🇷 · Yuta Orikasa🇨🇿

    We study one-loop induced radiative seesaw model applying a modular $A_4$ flavor symmetry, in which the neutrino mass matrix is achieved by two different Yukawa couplings one of which also contributes to positive value of muon anomalous magnetic moment as well as lepton flavor violations. Thanks to the specific mass matrix via $A_4$ symmetry and its modular weight, we find several predictions for lepton sector through our numerical analysis.

    hep-ph70 citations
18. 18*

    Primordial Power Spectra of Cosmological Fluctuations with Generalized Uncertainty Principle and Maximum Length Quantum Mechanics

    F. Skara🇬🇷 · L. Perivolaropoulos🇬🇷

    The existence of the cosmological particle horizon as the maximum measurable length $l_{max}$ in the universe leads to a generalization of the quantum uncertainty principle (GUP) to the form $\Delta x\Delta p\ge \frac{\hslash }{2}\frac{1}{1-\alpha \Delta x^2}$, where $\alpha \equiv l_{max}^{-2}$. The effects of this GUP on simple quantum mechanical systems has been shown recently by one of the authors\cite{Perivolaropoulos:2017rgq} to be extremely small (beyond current measurements) due to the extremely large scale of the current particle horizon. This is not the case in the Early Universe during the quantum generation of the inflationary primordial fluctuation spectrum. We estimate the effects of such GUP on the primordial fluctuation spectrum and on the corresponding spectral index. We generalize the field commutation (GFC) relation to $[\phi (k),{\pi }_{\phi }(k^{\prime })]$=$i\delta (k-k^{\prime })\frac{1}{1-\mu {\phi }^2(k)}$, where $\mu \sim {\alpha }^2\equiv l_{max}^{-4}$ is a GFC parameter, $\phi$ denotes a scalar field and ${\pi }_{\phi }$ denotes its canonical conjugate momentum. We obtain the predicted primordial perturbation spectrum as $P_S(k)=P_S^{(0)}(k)\left(1+\frac{\bar{\mu }}{k}\right)$ where $\bar{\mu }\equiv \mu V_{\ast }\simeq \sqrt{\alpha }=l_{max}^{-1}$ (here $V_{\ast }\simeq l_{max}^3$ is the volume corresponding to $l_{max}$) and $P_S^{(0)}(k)$ is the standard primordial spectrum obtained in the context of the Heisenberg uncertainty principle ($\mu =0$). We show that the predicted scalar spectral index is $n_s=1-\lambda -\frac{\bar{\mu }}{k}$ where $\lambda$ is a slow-roll parameter. Using observational constraints on the scale dependence of the spectral index $n_s$ we show that the $2\sigma$ range of $\alpha$ corresponds to $l_{max}\gtrsim 10^{26}m$ which is of the same order as the current particle horizon.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2019)·25 citations
19. 19*

    Updated results on neutrino mass and mass hierarchy from cosmology with Planck 2018 likelihoods

    Shouvik Roy Choudhury🇮🇳 · Steen Hannestad🇩🇰

    In this work we update the bounds on $\sum m_{\nu }$ from latest publicly available cosmological data and likelihoods using Bayesian analysis, while explicitly considering particular neutrino mass hierarchies. In the minimal $\Lambda \text{CDM}+\sum m_{\nu }$ model with most recent CMB data from Planck 2018 TT,TE,EE, lowE, and lensing; and BAO data from BOSS DR12, MGS, and 6dFGS, we find that at 95\% C.L. the bounds are: $\sum m_{\nu }<0.12$ eV (degenerate), $\sum m_{\nu }<0.15$ eV (normal), $\sum m_{\nu }<0.17$ eV (inverted). The bounds vary across the different mass orderings due to different priors on $\sum m_{\nu }$. Also, we find that the normal hierarchy is very mildly preferred relative to the inverted, using both minimum ${\chi }^2$ values and Bayesian Evidence ratios. In this paper we also provide bounds on $\sum m_{\nu }$ considering different hierarchies in various extended cosmological models: $\Lambda \text{CDM}+\sum m_{\nu }+r$, $w\text{CDM}+\sum m_{\nu }$, $w_0{w}_a\text{CDM}+\sum m_{\nu }$, $w_0{w}_a\text{CDM}+\sum m_{\nu }$ with $w(z)\ge -1$, $\Lambda \text{CDM}+\sum m_{\nu }+{\Omega }_k$, and $\Lambda \text{CDM}+\sum m_{\nu }+A_{\text{Lens}}$. We do not find any strong evidence of normal hierarchy over inverted hierarchy in the extended models either.

    ↳ astro-ph.COhep-exhep-phJCAP(2020)·185 citations
20. 20*

    Constraints on Light Dark Matter Particles Interacting with Electrons from DAMIC at SNOLAB

    A. Aguilar-Arevalo🇲🇽 · D. Amidei🇺🇸 · D. Baxter🇺🇸 · G. Cancelo🇺🇸 · B.A. Cervantes Vergara🇲🇽 · A.E. Chavarria🇺🇸 · E. Darragh-Ford🇺🇸 · J.R.T. de Mello Neto🇧🇷 · J.C. D'Olivo🇲🇽 · J. Estrada🇺🇸 · R. Gaïor🇫🇷 · Y. Guardincerri🇺🇸 and 22 other authors

    We report direct-detection constraints on light dark matter particles interacting with electrons. The results are based on a method that exploits the extremely low levels of leakage current of the DAMIC detector at SNOLAB of 2-6$\times$10${}^{-22}$ A cm${}^{-2}$. We evaluate the charge distribution of pixels that collect $<10{\mathrm{e}}^{-}$ for contributions beyond the leakage current that may be attributed to dark matter interactions. Constraints are placed on so-far unexplored parameter space for dark matter masses between 0.6 and 100 MeV$c^{-2}$. We also present new constraints on hidden-photon dark matter with masses in the range $1.2$-$30$ eV$c^{-2}$.

    ↳ astro-ph.COhep-exhep-phphysics.ins-detPRL(2019)·312 citations
21. 21*

    Generalizations of the Sommerfield and Schwinger models

    Howard Georgi🇺🇸 · Brian Warner🇺🇸

    The Sommerfield model with a massive vector field coupled to a massless fermion in 1+1 dimensions is an exactly solvable analog of a Bank-Zaks model. The "physics" of the model comprises a massive boson and an unparticle sector that survives at low energy as a conformal field theory (Thirring model). We analyze generalizations of the Sommerfield model, and the corresponding generalizations of the Schwinger model, with more massless fermions and more vector fields.

    ↳ hep-thhep-phJHEP(2020)·8 citations
22. 22*

    Production of multi-charmed hadrons by recombination in heavy ion collisions

    Sungtae Cho🇰🇷 · Su Houng Lee🇰🇷

    We study the production of multi-charmed hadrons by recombination in heavy ion collisions by focusing on the production of ${\Xi }_{cc}$, ${\Xi }_{cc}^{\ast }$, ${\Omega }_{scc}$, ${\Omega }_{scc}^{\ast }$, ${\Omega }_{ccc}$ baryons and X(3872) mesons. Starting from the estimation of yields for those hadrons at chemical freeze-out in both the statistical and coalescence model, we evaluate their transverse momentum distributions at mid-rapidity in the coalescence model. We show that yields of multi-charmed hadrons in heavy ion collisions at RHIC and LHC are large enough, and thereby not only multi-charmed hadrons observed so far, e.g., the ${\Xi }_{cc}$ but also those which have not been observed yet, can be discovered sufficiently in heavy ion collisions. We also find that the transverse momentum distribution ratio between various multi-charmed hadrons sensitively reflects the interplay between quark contents of corresponding hadrons as well as the transverse momentum distribution of charm quarks at the hadronization point, and therefore we insist that studying both the transverse momentum distributions of multi-charmed hadrons themselves and transverse momentum distribution ratios between various multi-charmed hadrons provide us with useful information on hadron production mechanism involving charm quarks in heavy ion collisions.

    ↳ nucl-thhep-phnucl-exPRC(2020)·29 citations
23. 23*

    Domain walls in neutron ${}^3{P}_2$ superfluids in neutron stars

    Shigehiro Yasui🇯🇵 · Muneto Nitta🇯🇵

    We work out domain walls in neutron ${}^3{P}_2$ superfluids realized in the core of neutron stars. Adopting the Ginzburg-Landau (GL) theory as a bosonic low-energy effective theory, we consider configurations of domain walls interpolating ground states, i.e., the uniaxial nematic (UN), D${}_2$-biaxial nematic (D${}_2$-BN), and D${}_4$-biaxial nematic (D${}_4$-BN) phases in the presence of zero, small and large magnetic fields, respectively. We solve the Euler-Lagrange equation from the GL free energy density, and calculate surface energy densities of the domain walls. We find that one extra Nambu-Goldstone mode is localized in the vicinity of a domain wall in the UN phase while a U(1) symmetry restores in the vicinity of one type of domain wall in the D${}_2$-BN phase and all domain walls in the D${}_4$-BN phase. Considering a pile of domain walls in the neutron stars, we find that the most stable configurations are domain walls perpendicular to the magnetic fields piled up in the direction along the magnetic fields in the D${}_2$-BN and D${}_4$-BN phases. We estimate the energy released from the deconstruction of the domain walls in the edge of a neutron star, and show that it can reach an astrophysical scale such as glitches in neutron stars.

    ↳ nucl-thastro-ph.HEhep-phhep-thPRC(2020)·17 citations
24. 24*

    Coupling Constant Corrections in a Holographic Model of Heavy Ion Collisions with Nonzero Baryon Number Density

    Åsmund Folkestad🇺🇸 · Sašo Grozdanov🇺🇸 · Krishna Rajagopal🇺🇸 · Wilke van der Schee🇨🇭

    Sufficiently energetic collisions of heavy ions result in the formation of a droplet of a strongly coupled liquid state of QCD matter known as quark-gluon plasma. By using gauge-gravity duality (holography), a model of a rapidly hydrodynamizing and thermalizing process like this can be constructed by colliding sheets of energy density moving at the speed of light and tracking the subsequent evolution. In this work, we consider the dual gravitational description of such collisions in the most general bulk theory with a four-derivative gravitational action containing a dynamical metric and a gauge field in five dimensions. Introducing the bulk gauge field enables the analysis of collisions of sheets which carry nonzero "baryon" number density in addition to energy density. Introducing the four-derivative terms enables consideration of such collisions in a gauge theory with finite gauge coupling, working perturbatively in the inverse coupling. While the dynamics of energy and momentum in the presence of perturbative inverse-coupling corrections has been analyzed previously, here we are able to determine the effect of such finite coupling corrections on the dynamics of the density of a conserved global charge, which we take as a model for the dynamics of nonzero baryon number density. In accordance with expectations, as the coupling is reduced we observe that after the collisions less baryon density ends up stopped at mid-rapidity and more of it ends up moving near the lightcone.

    ↳ hep-thhep-phnucl-exnucl-thJHEP(2019)·16 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.