We analyze how the crust equation of state affects several neutron star properties and how it impacts on possible constraints inferred from astrophysical observations. Using three distinct crusts, we generate three sets of model-independent equations of state describing stellar matter from a Taylor expansion around saturation density. The equations of state are thermodynamically consistent, causal, and compatible with astrophysical observations. The relations between the tidal deformability $\mathrm{\Lambda }$ and compactness $C$, Love number $k_2$ and radius of neutron star with mass $M$ are studied, and the effect of the crust equation of state on these relations analyzed. In most of the relations, the impact of the crust equation of state is not larger that 2%. If, however, a fixed neutron star mass is considered, the relation between the tidal deformability and the radius depends on the crust. We have found that the relation ${\mathrm{\Lambda }}_{M_i}=\alpha R_{M_i}^{\beta }$ becomes almost exact and crust independent for massive neutron stars. It is shown that it is possible to determine the tidal deformability of an $1.4M_{\odot }$ star from the GW179817 effective tidal deformability $\tilde{\mathrm{\Lambda }}$ with an accuracy of at least $\approx 10\%$. A high correlation between $\tilde{\mathrm{\Lambda }}$ and the radius of the most massive star of the neutron star binary was confirmed, however, it was demonstrated that the crust has an effect of $\approx 14\%$ on this relation. We have found that the relation ${\mathrm{\Lambda }}_1/{\mathrm{\Lambda }}_2=q^a$ depends on $M_{\text{chirp}}$ as $a\sim \sqrt{M_{\text{chirp}}}$.

The RG improvement of the screened massive expansion is studied at one loop in two renormalization schemes, the momentum subtraction (MOM) scheme and the screened momentum subtraction scheme. The respective Taylor-scheme running couplings are shown not to develop a Landau pole, provided that the initial value of the coupling is sufficiently small. The improved ghost and gluon propagators are found to behave as expected, displaying dynamical mass generation for the gluons and the standard UV limit of ordinary perturbation theory. In the MOM scheme, when optimized by matching with the fixed-coupling framework, the approach proves to be a powerful method for obtaining propagators, which are in excellent agreement with the lattice data already at one loop. After optimization, the gluon mass parameter is left as the only free parameter of the theory and is shown to play the same role of the ordinary perturbative QCD scale ${\mathrm{\Lambda }}_{\mathrm{QCD}}$.

The present study is a response to the raising comments on Brans-Dicke scalar field cosmological models in Lyra’s geometry [A. K. Yadav, Phys. Rev. D 10, 108301 (2020)] by Dr. Anil Kumar Yadav. We have corrected the manuscripts and remove the contradictions observed by the comment author. Now, the present cosmological model is a transit phase model with Brans-Dicke coupling constant $\omega <-1.33$ while the equation of state parameter (EoS) lies in the range $0\le \gamma <0.33$. The Brans-Dicke scalar field is responsible candidate for the acceleration in expansion of the universe.

In the present study, we comment on Brans-Dicke scalar field cosmological model in Lyra’s geometry [Maurya and Zia, Phys. Rev. D 100, 023503 (2019)]. In this comment, we investigate that there is no acceleration in the model proposed by the authors of Phys. Rev. D 100, 023503 (2019). Therefore, despite the claims to the contrary the Brans-Dicke scalar field cosmological model in Lyra’s geometry with high Brans-Dicke (BD) coupling parameter $\omega$ and constant $\beta$ cannot produce late time acceleration in the universe.

In this paper we apply a recently proposed numerical algorithm for finding stationary phase points in spin foam amplitudes. We study a spin foam amplitude with three vertices and a bulk face in 4D BF theory. We fix the boundary coherent states to three possible triangulations, one with zero deficit angle on the bulk face and two with nonzero deficit angle. We compute the amplitude numerically and we find a stationary phase point already at low spins in all the three cases. We comment on how this result contrasts with the claims of flatness problem in spin foam theories. We point out where these arguments may be misleading and we propose further computations to definitively answer the question.

The Fourier transform of the density-density correlation function in a Bose-Einstein condensate (BEC) analog black hole is a useful tool to investigate correlations between the Hawking particles and their partners. It can be expressed in terms of $⟨{{}^{\mathrm{out}}\widehat{a}}_{\mathrm{up}}^{\mathrm{ext}}{{}^{\mathrm{out}}\widehat{a}}_{\mathrm{up}}^{\mathrm{int}}⟩$, where ${{}^{\mathrm{out}}\widehat{a}}_{\mathrm{up}}^{\mathrm{ext}}$ is the annihilation operator for the Hawking particle and ${{}^{\mathrm{out}}\widehat{a}}_{\mathrm{up}}^{\mathrm{int}}$ is the corresponding one for the partner. This basic quantity is calculated for three different models for the BEC flow. It is shown that in each model the inclusion of the effective potential in the mode equations makes a significant difference. Furthermore, particle production induced by this effective potential in the interior of the black hole is studied for each model and shown to be nonthermal. An interesting peak that is related to the particle production and is present in some models is discussed.

Analogue black holes, which can mimic the kinetic aspects of real black holes, have been proposed for many years. The growth of the radial momentum toward the acoustic horizon is calculated for acoustic black holes in flat and curved spacetimes. Surprisingly, for a freely infalling vortex approaching the acoustic black hole, the Lyapunov exponent of the growth of the momentum at the horizon saturates the chaos bound ${\mathrm{\Lambda }}_{\text{Lyapunov}}\le 2\pi T$. We investigate the orbits of test vortices and sound wave rays in the ($2+1$)-dimensional “curved” spacetime of an acoustic black hole. We show that the vortices orbit, the sound wave orbit, and the time delay of sound are similar to those famous effects of general relativity. These effects can be verified experimentally in future experiments.

An axial-symmetric vacuum solution of the Einstein equations containing a supertranslation field diffeomorphic to the Schwarzschild solution is discussed in the context of the Israel theorem. The metric satisfies all conditions of the Israel theorem except for the condition on the form of the metric at spatial infinity. Nevertheless, following the steps of the proof of the theorem, we show that the proof applies to the metric with a supertranslation field and that the (transformed) metric used in the proof is spherically symmetric. We explain the source of the seeming discrepancy.

We study matter density perturbations up to third order and the one-loop matter power spectrum in degenerate higher-order scalar-tensor (DHOST) theories beyond Horndeski. We systematically solve gravitational field equations and fluid equations order by order and find three novel shape functions characterizing the third-order solution in DHOST theories. A complete form of the one-loop matter power spectrum is then obtained using the resultant second- and third-order solutions. We confirm the previous result that the convergence condition of the loop integrals in the infrared limit becomes more stringent than that of the standard one in general relativity. We show that also in the ultraviolet limit the convergence condition becomes more stringent and the one-loop matter power spectrum is thus sensitive to the short-wavelength behavior of the linear power spectrum.

Fast and accurate simulations of the nonlinear evolution of the cosmic density field are a major component of many cosmological analyses, but the computational time and storage required to run them can be exceedingly large. For this reason, we use generative adversarial networks (GANs) to learn a compressed representation of the 3D matter density field that is fast and easy to sample, and for the first time show that GANs are capable of generating samples at the level of accuracy of other conventional methods. Using subvolumes from a suite of GADGET-2 $N$-body simulations, we demonstrate that a deep-convolutional GAN can generate samples that capture both large- and small-scale features of the matter density field, as validated through a variety of $n$-point statistics. The use of a data scaling that preserves high-density features and a heavy-tailed latent space prior allow us to obtain state of the art results for fast 3D cosmic web generation. In particular, the mean power spectra from generated samples agree to within 5% up to $k=3$ and within 10% for $k\le 5$ when compared with $N$-body simulations, and similar accuracy is obtained for a variety of bispectra. By modeling the latent space with a heavy-tailed prior rather than a standard Gaussian, we better capture sample variance in the high-density voxel PDF and reduce errors in power spectrum and bispectrum covariance on all scales. Furthermore, we show that a conditional GAN can smoothly interpolate between samples conditioned on redshift. Deep generative models, such as the ones described in this work, provide great promise as fast, low-memory, high-fidelity forward models of large-scale structure.

The simulation of real-time dynamics in lattice gauge theories is particularly hard for classical computing due to the exponential scaling of the required resources. On the other hand, quantum algorithms can potentially perform the same calculation with a polynomial dependence on the number of degrees of freedom. A precise estimation is however particularly challenging for the simulation of lattice gauge theories in arbitrary dimensions, where gauge fields are dynamical variables, in addition to the particle fields. Moreover, there exist several choices for discretizing particles and gauge fields on a lattice, each of them coming at different prices in terms of qubit register size and circuit depth. Here we provide a resource counting for real-time evolution of $U(1)$ gauge theories, such as quantum electrodynamics, on arbitrary dimension using the Wilson fermion representation for the particles, and the quantum link model approach for the gauge fields. We study the phenomena of flux-string breaking up to a genuine bidimensional model using classical simulations of the quantum circuits and discuss the advantages of our discretization choice in simulation of more challenging $SU(N)$ gauge theories such as quantum chromodynamics.

Alerted by the recent LHCb discovery of exotic hadrons in the range (6.2 6.9) GeV, we present new results for the doubly-hidden scalar heavy $(\overline{Q}Q)(Q\overline{Q})$ charm and beauty molecules using the inverse Laplace transform sum rule (LSR) within stability criteria and including the next-to-leading order (NLO) factorized perturbative and $⟨G^3⟩$ gluon condensate corrections. We also critically revisit and improve existing lowest order (LO) QCD spectral sum rules (QSSR) estimates of the $(\overline{Q}\overline{Q})(QQ)$ tetraquarks analogous states. In the example of the antiscalar-scalar molecule, we separate explicitly the contributions of the factorized and nonfactorized contributions to LO of perturbative QCD and to the $⟨{\alpha }_s{G}^2⟩$ gluon condensate contributions in order to disprove some criticisms on the (mis)uses of the sum rules for four-quark currents. We also reemphasize the importance to include PT radiative corrections for heavy quark sum rules in order to justify the (ad hoc) definition and value of the heavy quark mass used frequently at LO in the literature. Our LSR results for tetraquark masses summarized in Table II are compared with the ones from ratio of moments (MOM) at NLO and results from LSR and ratios of MOM at LO (Table IV). The LHCb broad structure around (6.2–6.7) GeV can be described by the ${\overline{\eta }}_c{\eta }_c$, $\overline{J/\psi }J/\psi$ and ${\overline{\chi }}_{c1}{\chi }_{c1}$ molecules or/and their analogue tetraquark scalar-scalar, axial-axial and vector-vector lowest mass ground states. The peak at (6.8–6.9) GeV can be likely due to a ${\overline{\chi }}_{c0}{\chi }_{c0}$ molecule or/and a pseudoscalar-pseudoscalar tetraquark state. Similar analysis is done for the scalar beauty states whose masses are found to be above the ${\overline{\eta }}_b{\eta }_b$ and $\overline{\mathrm{\Upsilon }}(1S)\mathrm{\Upsilon }(1S)$ thresholds.

We show that the holographic $\mathrm{complexity}=\mathrm{volume}$ proposal satisfies a very general notion of momentum/complexity correspondence (PC), based on the momentum constraint of general relativity. It relates the rate of complexity variation with an appropriate matter momentum flux through spacelike extremal surfaces. This formalizes the intuitive idea that “gravitational clumping” of matter increases complexity, and the required notion of “infall momentum” is shown to have a Newtonian avatar which expresses this idea. The proposed form of the PC correspondence is found to be exact for any solution of Einstein’s equations in $2+1$ dimensions, and any spherically symmetric solution in arbitrary dimensions, generalizing all previous calculations using spherical thin shells. Gravitational radiation enters through a correction which does not have a straightforward interpretation as a PC correspondence. Other obstructions to an exact PC duality have a topological origin and arise in the presence of wormholes.

Flavor violating processes in the lepton sector have highly suppressed branching ratios in the standard model, mainly due to the tiny neutrino mass. This means that observing a lepton flavor violation (LFV) in the next round of experiments would constitute a clear indication of physics beyond the standard model (BSM). We revisit a discussion of one possible way to search for LFV, muonium-antimuonium oscillations. This process violates the muon lepton number by two units and could be sensitive to the types of BSM physics that are not probed by other types of LFV processes. Using techniques of effective field theory, we calculate the mass and width differences of the mass eigenstates of muonium. We argue that its invisible decays give the parametrically leading contribution to the lifetime difference and put constraints on the scales of new physics probed by effective operators in muonium oscillations.

Assuming that the degrees of freedom of a black hole are finite in number and of fermionic nature, we naturally obtain, within a second-quantized toy model of the evaporation, that the Bekenstein bound is a consequence of the Pauli exclusion principle for these fundamental degrees of freedom. We show that entanglement, Bekenstein, and thermodynamic entropies of the black hole all stem from the same approach, based on the entropy operator whose structure is the one typical of Takahashi and Umezawa’s thermofield dynamics. We then evaluate the von Neumann black hole-environment entropy and noticeably obtain a Page-like evolution. We finally show that this is a consequence of a duality between our model and a quantum dissipativelike fermionic system.

This paper studies cross sections inside black holes and conjectures a universal inequality: in a static ($d+1$)-dimensional asymptotically planar/spherical Schwarzschild-AdS spacetime of given energy $E$ and AdS radius ${\ell }_{\mathrm{AdS}}$, the “size of cross section” inside black holes is bounded by $8\pi E{\ell }_{\mathrm{AdS}}/(d-1)$. To support this conjecture, it gives the proofs for cases with spherical/planar symmetries and some special cases without planar/spherical symmetries. As one corollary, it shows that the complexity growth rate in complexity-volume conjecture satisfies the upper bound argued by quantum information theory. This makes a first step toward proving the conjecture that the vacuum black hole has fastest complexity growth in the systems of same energy. It also finds a similar bound for asymptotically flat black holes, which gives us an estimation on the largest interior volume of a large evaporating black hole.

The second law of thermodynamics is discussed and reformulated from a quantum information theoretic perspective for open quantum systems using relative entropy. Specifically, the relative entropy of a quantum state with respect to equilibrium states is considered and its monotonicity property with respect to an open quantum system evolution is used to obtain second lawlike inequalities. We discuss this first for generic quantum systems in contact with a thermal bath and subsequently turn to a formulation suitable for the description of local dynamics in a relativistic quantum field theory. A local version of the second law similar to the one used in relativistic fluid dynamics can be formulated with relative entropy or even relative entanglement entropy in a space-time region bounded by two light cones. We also give an outlook toward isolated quantum field theories and discuss the role of entanglement for relativistic fluid dynamics.

The parity transformation law of the fermion field $\psi (x)$ is usually defined by the “${\gamma }^0$ parity” ${\psi }^p(t,-\overrightarrow{x})={\gamma }^0\psi (t,-\overrightarrow{x})$ with eigenvalues $\pm 1$, while the “$i{\gamma }^0$ parity” ${\psi }^p(t,-\overrightarrow{x})=i{\gamma }^0\psi (t,-\overrightarrow{x})$ is required for the Majorana fermion. The compatibility issues of these two parity laws arise in generic fermion number violating theories where a general class of Majorana fermions appear. In the case of Majorana neutrinos constructed from chiral neutrinos in an extension of the Standard Model, the Majorana neutrinos can be characterized by $CP$ symmetry although $C$ and $P$ are separately broken. It is then shown that either choice of the parity operation, ${\gamma }^0$ or $i{\gamma }^0$, in the level of the starting fermions gives rise to the consistent and physically equivalent descriptions of emergent Majorana neutrinos both for Weinberg’s model of neutrinos and for a general class of seesaw models. The mechanism of this equivalence is that the Majorana neutrino constructed from a chiral neutrino, which satisfies the classical Majorana condition $\psi (x)=C{\overline{\psi (x)}}^T$, allows the phase freedom $\psi (x)=e^{i\alpha }{\nu }_L(x)+e^{-i\alpha }C{\overline{{\nu }_L(x)}}^T$ with $\alpha =0$ or $\pi /4$. This accounts for the phase coming from the different definitions of parity for ${\nu }_L(x)$ and ensures the consistent definitions of $CP$ symmetry $(\mathcal{C}\mathcal{P})\psi (x)(\mathcal{C}\mathcal{P}{)}^{†}=\pm i{\gamma }^0\psi (t,-\overrightarrow{x})$.

We present the first numerical relativity waveforms for binary black hole mergers produced using spectral methods that show both the displacement and the spin memory effects. Explicitly, we use the SXS (Simulating eXtreme Spacetimes) Collaboration’s spec code to run a Cauchy evolution of a binary black hole merger and then extract the gravitational wave strain using spectre’s version of a Cauchy-characteristic extraction. We find that we can accurately resolve the strain’s traditional $m=0$ memory modes and some of the $m\ne 0$ oscillatory memory modes that have previously only been theorized. We also perform a separate calculation of the memory using equations for the Bondi-Metzner-Sachs charges as well as the energy and angular momentum fluxes at asymptotic infinity. Our new calculation uses only the gravitational wave strain and two of the Weyl scalars at infinity. Also, this computation shows that the memory modes can be understood as a combination of a memory signal throughout the binary’s inspiral and merger phases, and a quasinormal mode signal near the ringdown phase. Additionally, we find that the magnetic memory, up to numerical error, is indeed zero as previously conjectured. Last, we find that signal-to-noise ratios of memory for LIGO, the Einstein Telescope, and the Laser Interferometer Space Antenna with these new waveforms and new memory calculation are larger than previous expectations based on post-Newtonian or minimal waveform models.