Recently, Cheng et al. identified a number of massive white dwarfs (WD) that appear to have an additional heat source providing a luminosity near $\approx {10}^{-3}{L}_{\odot }$ for multiple Gyr [S. Cheng, J. D. Cummings, and B. Ménard, Astrophys. J. 886, 100 (2019)]. In this paper we explore heating from electron capture and pycnonuclear reactions. We also explore heating from dark matter annihilation. WD stars appear to be too small to capture enough dark matter for this to be important. Finally, if dark matter condenses to very high densities inside a WD this could ignite nuclear reactions. We calculate the enhanced central density of a WD in the gravitational potential of a very dense dark matter core. While this might start a supernova, it seems unlikely to provide modest heating for a long time. We conclude that electron capture, pycnonuclear, and dark matter reactions are unlikely to provide significant heating in the massive WD that Cheng considers.

Higher-order repulsive interactions are included in the three-flavor Nambu–Jona-Lasinio model in order to describe the quark phase of an hybrid star. The effect of 4-quark and 8-quark vector-isoscalar interactions in the stability of hybrid star configurations is analyzed. The presence of a 8-quark vector-isoscalar channel is seen to be crucial in generating large quark branches in the $M(R)$ diagram. This is due to its stiffening effect on the quark matter equation of state which arises from the nonlinear density dependence of the speed of sound. This additional interaction channel allows for the appearance of a quark core at moderately low NS masses, $\sim 1M_{\odot }$, and provides the required repulsion to preserve the star stability up to $\sim 2.1M_{\odot }$. Furthermore, we show that both the heaviest NS mass generated, $M_{\max }$, and its radius, $R_{\max }$, are quite sensitive to the strength of 8-quark vector-isoscalar channel, leading to a considerable decrease of $R_{\max }$ as the coupling increases. This behavior imprints a considerable deviation from the purely hadronic matter equation of state in the $\mathrm{\Lambda }(M)$ diagram, which might be a possible signature of the quark matter existence, even for moderately low NS masses, $\sim 1.4M_{\odot }$. The resulting $M(R)$ and $\mathrm{\Lambda }(R)$ relations are in accordance with the latest astrophysical constraints from NICER and LIGO/Virgo observations, respectively.

Rotating neutron star or pulsar can be a possible source of pseudo Nambu Goldstone bosons or axions which can mediate long range axionic hair outside of the pulsar. When the electromagnetic radiation is emitted from a pulsar and passes through the long range axion hair, the axion rotates the polarization of the electromagnetic radiation and produces birefringence. We obtain the angle of birefringence due to this long range axionic hair as 0.42°. This value is within the accuracy of measuring the linear polarization angle of pulsar light which is $\le 1.0°$. Our result continues to hold as long as the range of the axion hair (inverse of axion mass) is greater than the radius of the pulsar, i.e., $m_a<{10}^{-11}\mathrm{eV}$ and the axion decay constant $f_a\lesssim \mathcal{O}({10}^{17}\mathrm{GeV})$.

We present the results of the first combined dark matter search targeting the Galactic Center using the ANTARES and IceCube neutrino telescopes. For dark matter particles with masses from 50 to 1000 GeV, the sensitivities on the self-annihilation cross section set by ANTARES and IceCube are comparable, making this mass range particularly interesting for a joint analysis. Dark matter self-annihilation through the ${\tau }^{+}{\tau }^{-}$, ${\mu }^{+}{\mu }^{-}$, $b\overline{b}$, and $W^{+}{W}^{-}$ channels is considered for both the Navarro-Frenk-White and Burkert halo profiles. In the combination of 2101.6 days of ANTARES data and 1007 days of IceCube data, no excess over the expected background is observed. Limits on the thermally averaged dark matter annihilation cross section $⟨{\sigma }_A\upsilon ⟩$ are set. These limits present an improvement of up to a factor of 2 in the studied dark matter mass range with respect to the individual limits published by both collaborations. When considering dark matter particles with a mass of 200 GeV annihilating through the ${\tau }^{+}{\tau }^{-}$ channel, the value obtained for the limit is $7.44\times {10}^{-24}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ for the Navarro-Frenk-White halo profile. For the purpose of this joint analysis, the model parameters and the likelihood are unified, providing a benchmark for forthcoming dark matter searches performed by neutrino telescopes.

We discuss chiral separation effect in the systems with spatial nonhomogeneity. It may be caused by nonuniform electric potential or by another reasons, which do not, however, break chiral symmetry of an effective low energy theory. Such low energy effective theory describes quasiparticles close to the Fermi surfaces. In the presence of constant external magnetic field the nondissipative axial current appears. It appears that its response to chemical potential and magnetic field (the CSE conductivity) is universal. It is robust to smooth modifications of the system and is expressed through an integral over a surface in momentum space that surrounds all singularities of the Green function. In itself this expression represents an extension of the topological invariant protecting Fermi points to the case of inhomogeneous systems.

We compute the general expression of the one-loop vertex correction in an arbitrary plane-wave background field for the case of two on-shell external electrons and an off-shell external photon. The properties of the vertex corrections under gauge transformations of the plane-wave background field and of the radiation field are studied. Concerning the divergences of the vertex correction, the infrared one is cured by assigning a finite mass to the photon, whereas the ultraviolet one is shown to be renormalized exactly as in vacuum. Finally, the corresponding expression of the vertex correction within the locally constant crossed field approximation is also derived and the high-field asymptotic is shown to scale according to the Ritus-Narozhny conjecture, although the terms featuring the leading-order dependence on the field are found not to contribute to physical transition amplitudes.

In a series of recent works, Ishihara and Ogawa have investigated nontopological solitons (Q-balls) in a spontaneously broken Abelian gauge theory coupled to two complex scalar fields. The present paper extends their investigations to the most general $\mathrm{U}(1)\times \mathrm{U}(1)$ symmetric quartic potential. Also, a new class of charged Q-ball solutions with vanishing self-interaction terms is investigated and some of their remarkable properties are exhibited.

We investigate the phase transition from hadron to quark matter in the general case without the assumption of chemical equilibrium. The effects of net strangeness on charge and isospin fractions, chemical potentials, and temperature are studied in the context of the Chiral Mean Field (CMF) model that incorporates chiral symmetry restoration and deconfinement. The extent to which these quantities are probed during deconfinement in conditions expected to exist in protoneutron stars, binary neutron-star mergers, and heavy-ion collisions is analyzed via the construction of 3-dimensional phase diagrams.

Supernovae can produce vast fluxes of new particles with masses on the MeV scale, a mass scale of interest for models of light dark matter. When these new particles become diffusively trapped within the supernova, the escaping flux will emerge semirelativistic with an order-one spread in velocities. As a result, overlapping emissions from Galactic supernovae will produce an overall flux of these particles at Earth that is approximately constant in time. However, this flux is highly anisotropic and is steeply peaked toward the Galactic center. This is in contrast with the cosmological abundance of a weakly interacting massive particles (WIMP)-like dark matter which, due to the rotation of the Galaxy, appears to come from the direction of the Cygnus constellation. In this paper, we demonstrate the need for a directional detector to efficiently discriminate between a signal from a cold cosmological abundance of GeV-scale WIMPs and a signal from a hot population of supernova-produced MeV-scale dark matter.

With the deeper study of Higgs particle, Higgs precision measurements can be served to probe new physics indirectly. In many new physics models, vectorlike quarks $T_L$, $T_R$ occur naturally. It is important to probe their couplings with standard model particles. In this work, we consider the singlet $T_L$, $T_R$ extended models and show how to constrain the $Tth$ couplings through the $h\to \gamma Z$ decay at high-luminosity LHC. First, we derive the perturbative unitarity bounds on $|y_{L,R}^{tT}|$ with other couplings set to be zeros simply. To optimize the situation, we take $m_T=400\mathrm{GeV}$ and $s_L=0.2$ considering the experimental constraints. Under this benchmark point, we find that the future bounds from $h\to \gamma Z$ decay can limit the real parts of $y_{L,R}^{tT}$ in the positive direction to be O(1) because of the double enhancement. For the real parts of $y_{L,R}^{tT}$ in the negative direction, it is always surpassed by the perturbative unitarity. Moreover, we find that the top quark electric dipole moment can give stronger bounds (especially the imaginary parts of $y_{L,R}^{tT}$) than the perturbative unitarity and $h\to \gamma Z$ decay in the off-axis regions for some scenarios.

We have recently shown that axions and axionlike particles (ALPs) may emit an observable stochastic gravitational wave (GW) background when they begin to oscillate in the early Universe. In this note, we identify the regions of ALP parameter space, which may be probed by future GW detectors, including ground- and space-based interferometers, and pulsar timing arrays. Interestingly, these experiments have the ability to probe axions from the bottom up, i.e., in the very weakly coupled regime, which is otherwise unconstrained. Furthermore, we discuss the effects of finite dark photon mass and kinetic mixing on the mechanism, as well as the (in)sensitivity to couplings of the axion to Standard Model fields. We conclude that realistic axion and ALP scenarios may indeed be probed by GW experiments in the future and provide signal templates for further studies.

We entertain the possibility that scalar leptoquarks (LQs) generate consequential effects on the strangeness-changing decays of hyperons and kaons involving missing energy carried away by a pair of invisible fermions. Although such processes have suppressed rates in the standard model (SM), they could get significant enhancement in the presence of the LQs. In order to respect the available data on the kaon modes $K\to \pi \nu \overline{\nu }$ and increase the rates of the hyperon decays substantially at the same time, two different scalar LQs are needed. If the LQs have Yukawa couplings solely to SM fermions, we find that the hyperon rates cannot attain values within the reach of ongoing or near-future experiments because of the combined constraints from the measurements on kaon mixing and lepton-flavor-violating processes. However, if we include light right-handed neutrinos in the LQ interactions, their contributions can evade the leading restrictions and translate into hyperon rates which may be big enough to be probed by upcoming searches. Thus, these hyperon modes could provide a new avenue for seeking sterile neutrinos.

In present work, we explore and experiment with an alternative approach to studying resonance properties in a finite volume. By analytic continuing the finite lattice size $L$ into a complex plane, the oscillating behavior of the finite volume Green’s function is mapped onto an infinite volume Green’s function that is corrected by exponentially decaying finite volume effect. The analytic continuation technique thus can be applied to study resonance properties directly in finite volume dynamical equations.

In this paper we study thermodynamic properties of dense cold $SU(2)$ QCD within lattice simulation with dynamical rooted staggered quarks which in the continuum limit correspond to $N_f=2$ quark flavours. We calculate baryon density, renormalized chiral and diquark condensates for various baryon chemical potentials in the region $\mu \in (0,2000)\mathrm{MeV}$. It is found that in the region $\mu \in (0,540)\mathrm{MeV}$ the system is well described by the ChPT predictions. In the region $\mu >540\mathrm{MeV}$ the system becomes sufficiently dense and ChPT is no longer applicable to describe lattice data. For chemical potentials $\mu >900\mathrm{MeV}$ we observe formation of the Fermi sphere, and the system is similar to the one described by the Bardeen-Cooper-Schrieffer theory where the diquarks play a role of Cooper pairs. In order to study how nonzero baryon density influences the gluon background we calculate chromoelectric and chromomagnetic fields, as well as the topological susceptibility. We find that the chromoelectric field and the topological susceptibility decrease, whereas the chromomagnetic field increases with rising of baryon chemical potential. Finally we study the equation of state of dense two-color quark matter.

In the simulation of QCD with $2+1$ flavors of Wilson fermions, the positivity of the fermion determinant is generally assumed. We present evidence that this assumption is in general not justified and discuss the consequences of this finding.

We construct a quantum mechanical matrix model that is a dimensional reduction of $\mathcal{N}=1$ super-Yang-Mills on $S^3\times \mathbb{R}$. We do so by pulling back the set of left-invariant connections of the gauge bundle onto the real superspace, with the spatial ${\mathbb{R}}^3$ compactified to $S^3$. We quantize the $\mathcal{N}=1$ $SU(2)$ matrix model in the weak-coupling limit $g\ll 1$, with $g$ the dimensionless gauge coupling constant, using the Born-Oppenheimer approximation and find that different superselection sectors emerge for the effective gluon dynamics in this regime, reminiscent of different phases of the full quantum theory. We demonstrate that the Born-Oppenheimer quantization is indeed compatible with supersymmetry, albeit in a subtle manner. In fact, we can define effective supercharges that relate the different sectors of the matrix model’s Hilbert space. These effective supercharges have a different definition in each phase of the theory.

Hexaquark wave function with the quantum numbers $I(J^P)=0(3^{+})$, which might be relevant for $d^{*}(2380)$, is constructed under an assumption that this is composed only of $u$, $d$ quarks in an $S$ wave. By combining three diquarks of either type, (${\overline{\mathbf{3}}}_c,I=1$) or (${\mathbf{6}}_c,I=0$), we demonstrate that there are five possible configurations for the six-quark state. The fully antisymmetric wave function is constructed by linearly combining the five configurations on an equal footing. We then take this wave function as well as the five configurations to calculate the hexaquark mass using the contact type effective potential consisting of the color spin, color electric, and constant shift. The mass is found to be the same regardless of the configurations being used including the fully antisymmetric one. This result can be traced to the fact that the hexaquark system has a freedom in choosing three diquarks in the construction of its wave function. The calculated hexaquark mass using the empirical parameters independently fixed from the baryon spectroscopy is found to be around 2342 MeV, which is indeed very close to the experimental mass of $d^{*}(2380)$. Therefore, the hexaquark picture is promising for $d^{*}(2380)$ as far as the mass is concerned.

In this paper we report on certain ambiguities in the calculation of the ensemble average $⟨T_{\mu \nu }⟩$ of the stress-energy-momentum tensor of an arbitrarily coupled massless scalar field in one-dimensional boxes in flat spacetime. The study addresses a box with periodic boundary conditions (a circle) and boxes with reflecting edges (with Dirichlet or Neumann boundary conditions at the end points). The expressions for $⟨{T^{\mu }}^{\nu }⟩$ are obtained from finite-temperature Green functions. In an appendix, in order to control divergences typical of two dimensions, these Green functions are calculated for related backgrounds with an arbitrary number of dimensions and for scalar fields of arbitrary mass, and are specialized in the text to two dimensions and for massless fields. The ambiguities arise due to the presence in $⟨{T^{\mu }}^{\nu }⟩$ of double series that are not absolutely convergent. The order in which the two associated summations are evaluated matters, leading to two different thermodynamics for each type of box. In the case of a circle, it is shown that the ambiguity corresponds to the classic controversy in the literature whether or not zero-mode contributions should be taken into account in computations of partition functions. In the case of boxes with reflecting edges, it results that one of the thermodynamics corresponds to a total energy (obtained by integrating the nonhomogeneous energy density over space) that does not depend on the curvature coupling parameter $\xi$ as expected, whereas the other thermodynamics curiously corresponds to a total energy that does depend on $\xi$. Thermodynamic requirements (such as local and global stability) and their restrictions on the values of $\xi$ are considered.

Unruh-deWitt detectors have been utilized widely as probes for quantum particles, entanglement and spacetime curvature. Here, we extend the standard treatment of an Unruh-deWitt detector interacting with a massless, scalar field to include the detector traveling in a quantum superposition of classical trajectories. We derive perturbative expressions for the final state of the detector, and show that it depends on field correlation functions evaluated locally along the individual trajectories, as well as nonlocally between the superposed trajectories. By applying our general approach to a detector traveling in a superposition of two uniformly accelerated trajectories, including those with equal and differing proper accelerations, we discover novel interference effects in the emission and absorption spectra. These effects can be traced to causal relations between the superposed trajectories. Finally, we show that in general, such a detector does not thermalize even if the superposed paths would individually yield the same thermal state.