In this paper, we find the heat capacity of the magnetic dual chiral density wave (MDCDW) phase of dense quark matter and use it to explore the feasibility of this phase for a neutron star interior. MDCDW is a spatially inhomogeneous phase of quark matter known to be favored at intermediate densities over the chirally symmetric phase and the color-flavor-locked superconducting phase. By comparing our result to the lower limit of the core heat capacity established from observations of transiently accreting neutron stars, we show that the heat capacity of MDCDW quark matter is well above that lower limit and hence cannot be ruled out. This result adds to a wealth of complementary investigations, all of which has served to strengthen the viability of a neutron star interior made of MDCDW quark matter. For completeness, we review the contributions to the heat capacity of the main neutron star ingredients at low, high, and intermediate densities, with and without the presence of a magnetic field.

Quantum noise limits the sensitivity of precision measurement devices, such as laser interferometer gravitational-wave observatories and axion detectors. In the shot-noise-limited regime, these resonant detectors are subject to a trade-off between the peak sensitivity and bandwidth. One approach to circumvent this limitation in gravitational-wave detectors is to embed an anomalous-dispersion optomechanical filter to broaden the bandwidth. The original filter cavity design, however, makes the entire system unstable. Recently, we proposed the coherent feedback between the arm cavity and the optomechanical filter to eliminate the instability via $PT$ symmetry [Li et al., arXiv:2012.00836]. The original analysis based upon the Hamiltonian formalism adopted the single-mode and resolved-sideband approximations. In this paper, we go beyond these approximations and consider realistic parameters. We show that the main conclusion concerning stability remains intact, with both Nyquist analysis and a detailed time-domain simulation.

The exceptional region of the parameter space (ERPS) of the two Higgs doublet model (2HDM) is defined to be the parameter regime where the scalar potential takes on a very special form. In the standard parametrization of the 2HDM scalar potential with squared mass parameters $m_{11}^2$, $m_{22}^2$, $m_{12}^2$, and dimensionless couplings, ${\lambda }_1,{\lambda }_2,\dots ,{\lambda }_7$, the ERPS corresponds to ${\lambda }_1={\lambda }_2$, ${\lambda }_7=-{\lambda }_6$, $m_{11}^2=m_{22}^2$ and $m_{12}^2=0$, corresponding to a scalar potential with an enhanced generalized $CP$ symmetry called GCP2. Many special features persist if ${\lambda }_1={\lambda }_2$ and ${\lambda }_7=-{\lambda }_6$ are retained while allowing for $m_{11}^2\ne m_{22}^2$ and/or $m_{12}^2\ne 0$, corresponding to a scalar potential with a softly broken GCP2 symmetry, which we designate as the ERPS4. In this paper, we examine many of the special features of the ERPS4, as well as even more specialized cases within the ERPS4 framework in which additional constraints on the scalar potential parameters are imposed. By surveying the landscape of the ERPS4, we complete the classification of 2HDM scalar potentials that exhibit an exact Higgs alignment (where the tree-level couplings of one neutral scalar coincide with those of the Standard Model Higgs boson), due to a residual symmetry that is unbroken in the vacuum. One surprising aspect of the ERPS4 is the possibility that the scalar sector is $CP$-conserving despite the presence of a complex parameter of the scalar potential whose complex phase cannot be removed by separate rephasings of the two scalar doublet fields. The significance of the ERPS4 regime for custodial symmetry is also discussed, and the cases where a custodial symmetric 2HDM scalar potential preserves an exact Higgs alignment are elucidated.

Tree-level dynamical stability of scalar field potentials in renormalizable theories can in principle be expressed in terms of positivity conditions on quartic polynomial structures. However, these conditions cannot always be cast in a fully analytical resolved form, involving only the couplings and being valid for all field directions. In this paper we consider such forms in three physically motivated models involving $SU(2)$ triplet scalar fields: the Type-II seesaw model, the Georgi-Machacek model, and a generalized two-triplet model. A detailed analysis of the latter model allows one to establish the full set of necessary and sufficient boundedness-from-below conditions. These can serve as a guide, together with unitarity and vacuum structure constraints, for consistent phenomenological (tree-level) studies. They also provide a seed for improved loop-level conditions and encompass in particular the leading ones for the more specific Georgi-Machacek case. Incidentally, we present complete proofs of various properties and also derive general positivity conditions on quartic polynomials that are equivalent to but much simpler than the ones used in the literature.

We present a calculation of the contribution of the $\mathrm{\Theta }$-term to the neutron and proton electric dipole moments using seven $2+1+1$-flavor highly improved staggered quark ensembles. We also estimate the topological susceptibility for the $2+1+1$ theory to be ${\chi }_Q=(66(9)(4)\mathrm{MeV}{)}^4$ in the continuum limit at $M_{\pi }=135\mathrm{MeV}$. The calculation of the nucleon three-point function is done using Wilson-clover valence quarks. The $\cancel{\mathrm{CP}}$ form factor $F_3$ is calculated by expanding in small $\mathrm{\Theta }$. We show that lattice artifacts introduce a term proportional to $a$ that does not vanish in the chiral limit, and we include this in our chiral-continuum fits. A chiral perturbation theory analysis shows that the $N(\mathbf{0})\pi (\mathbf{0})$ state should provide the leading excited-state contribution, and we study the effect of such a state. Detailed analysis of the contributions to the neutron and proton electric dipole moment using two strategies for removing excited-state contamination are presented. Using the excited-state spectrum from fits to the two-point function, we find $d_n^{\mathrm{\Theta }}$ is small, $|d_n^{\mathrm{\Theta }}|\lesssim 0.01\overline{\mathrm{\Theta }}\mathrm{e}·\mathrm{fm}$, whereas for the proton we get $|d_p^{\mathrm{\Theta }}|\sim 0.02\overline{\mathrm{\Theta }}\mathrm{e}·\mathrm{fm}$. On the other hand, if the dominant excited-state contribution is from the $N\pi$ state, then $|d_n^{\mathrm{\Theta }}|$ could be as large as $0.05\overline{\mathrm{\Theta }}\mathrm{e}·\mathrm{fm}$ and $|d_p^{\mathrm{\Theta }}|\sim 0.07\overline{\mathrm{\Theta }}\mathrm{e}·\mathrm{fm}$. Our overall conclusion is that present lattice QCD calculations do not provide a reliable estimate of the contribution of the $\mathrm{\Theta }$-term to the nucleon electric dipole moments, and a factor of 10 higher statistics data are needed to get better control over the systematics and possibly a $3\sigma$ result.

In recent years, the existence of a hadronically stable $\overline{b}\overline{b}ud$ tetraquark with quantum numbers $I(J^P)=0(1^{+})$ was confirmed by first principles lattice QCD computations. In this work we use lattice QCD to compare two frequently discussed competing structures for this tetraquark by considering meson-meson as well as diquark-antidiquark creation operators. We use the static-light approximation, where the two $\overline{b}$ quarks are assumed to be infinitely heavy with frozen positions, while the light $u$ and $d$ quarks are fully relativistic. By minimizing effective energies and by solving generalized eigenvalue problems we determine the importance of the meson-meson and the diquark-antidiquark creation operators with respect to the ground state. It turns out, that the diquark-antidiquark structure dominates for $\overline{b}\overline{b}$ separations $r\lesssim 0.25\mathrm{fm}$, whereas it becomes increasingly more irrelevant for larger separations, where the $I(J^P)=0(1^{+})$ tetraquark is mostly a meson-meson state. We also estimate the meson-meson to diquark-antidiquark ratio of this tetraquark and find around $60\%/40\%$.

We present a gauge invariant digitization of $(1+1)\mathrm{d}$ scalar quantum electrodynamics for an arbitrary spin truncation for qudit-based quantum computers. We provide a construction of the Trotter operator in terms of a universal qudit-gate set. The cost savings of using a qutrit based spin-1 encoding versus a qubit encoding are illustrated. We show that a simple initial state could be simulated on current qutrit based hardware using noisy simulations for two different native gate set.

Results of a search for new physics in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of $139{\mathrm{fb}}^{-1}$ at a center-of-mass energy of 13 TeV collected in the period 2015–2018 with the ATLAS detector at the Large Hadron Collider. Compared to previous publications, in addition to an increase of almost a factor of four in the data size, the analysis implements a number of improvements in the signal selection and the background determination leading to enhanced sensitivity. Events are required to have at least one jet with transverse momentum above 150 GeV and no reconstructed leptons ($e$, $\mu$ or $\tau$) or photons. Several signal regions are considered with increasing requirements on the missing transverse momentum starting at 200 GeV. Overall agreement is observed between the number of events in data and the Standard Model predictions. Model-independent 95% confidence-level limits on visible cross sections for new processes are obtained in the range between 736 fb and 0.3 fb. Results are also translated into improved exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, supersymmetric particles in several compressed scenarios, axionlike particles, and new scalar particles in dark-energy-inspired models. In addition, the data are translated into bounds on the invisible branching ratio of the Higgs boson.

Understanding the nature of the hidden charm pentaquark(like) signals in the LHCb data for ${\mathrm{\Lambda }}_b^0\to J/\psi p{K}^{-}$ is a central problem of hadron spectroscopy. We propose a scenario completely different from previous ones such as hadron molecules and compact pentaquarks. We identify relevant double triangle mechanisms with leading or lower-order singularities. The associated anomalous threshold cusps at the ${\mathrm{\Sigma }}_c^{(*)}{\overline{D}}^{(*)}$ thresholds are significantly more singular than the ordinary ones. Then we demonstrate that the double triangle amplitudes reproduce the peak structures of $P_c(4312{)}^{+}$, $P_c(4380{)}^{+}$, and $P_c(4457{)}^{+}$ in the LHCb data, through an interference with other common mechanisms. Only the $P_c(4440{)}^{+}$ peak is due to a resonance with a width and strength significantly smaller than previously estimated. $P_c^{+}$ signals are expected in other processes, and the proposed model (partly) explains the current data, such as the GlueX $J/\psi$ photoproduction data with no $P_c^{+}$ signals and the LHCb ${\mathrm{\Lambda }}_b^0\to J/\psi p{\pi }^{-}$ data with a possible signal only from $P_c(4440{)}^{+}$. In general, the double triangle singularity is now a possible option to interpret resonancelike structures near thresholds.

Recently, $\mathcal{O}({\alpha }^3)$ corrections to the muon decay rate and $\mathcal{O}({\alpha }_s^3)$ to heavy quark decays have been determined by Fael, Schönwald, and Steinhauser. This is the first such perturbative improvement of these important quantities in more than two decades. We reveal and explain a symmetry pattern in these new corrections, and confirm the most technically difficult parts of their evaluation.

String theory on ${\mathrm{AdS}}_3$ with NS-NS fluxes admits a solvable irrelevant deformation which is close to the $T\overline{T}$ deformation of the dual conformal field theory (${\mathrm{CFT}}_2$). This consists of deforming the world sheet action, namely the action of the $SL(2,\mathbb{R})$ Wess-Zumino-Witten model, by adding to it the operator $J^{-}{\overline{J}}^{-}$, constructed with two Kac-Moody currents. The geometrical interpretation of the resulting theory is that of strings on a conformally flat background that interpolate between anti–de Sitter (${\mathrm{AdS}}_3$) in the IR and a flat linear dilaton spacetime with its Hagedorn spectrum in the UV, having passed through a transition region of positive curvature. Here, we study the properties of this string background both from the point of view of the low-energy effective theory and of the world sheet CFT. We first study the geometrical properties of the semiclassical geometry, then we revise the computation of correlation functions and of the spectrum of the $J^{-}{\overline{J}}^{-}$ deformed world sheet theory, and finally we discuss how to extend this type of current-current deformation to other conformal models.

We study a five-dimensional $R$-charged black hole in extended thermodynamic space. Here, we consider pressure and volume as conjugate thermodynamic variables. We begin with a thermodynamic study based on Maxwell’s equal area rule and then compute the Ruppeiner scalar curvature for a number of different charge combinations. We mainly focus on three characteristic cases: an $R$-charged black hole with three equal charges, two equal charges, and three unequal charges. Based on our analysis, we make an attempt to relate the Ruppeiner scalar curvature with the phase structure of the black hole.

We study three different measures of quantum correlations—entanglement spectrum, entanglement entropy, and logarithmic negativity—for a ($1+1$)-dimensional massive scalar field in a flat space-time. The entanglement spectrum for the discretized scalar field in the ground state indicates a crossover in the zero-mode regime, which is further substantiated by an analytical treatment of both entanglement entropy and logarithmic negativity. The exact nature of this crossover depends on the boundary conditions used—the leading order term switches from a log to log-log behavior for the periodic and Neumann boundary conditions. In contrast, for Dirichlet, it is the parameters within the leading log-log term that are switched. We show that this crossover manifests as a change in the behavior of the leading order divergent term for entanglement entropy and logarithmic negativity close to the zero-mode limit. We thus show that the two regimes have fundamentally different information content. Furthermore, an analysis of the ground-state fidelity shows us that the region between critical point $\mathrm{\Lambda }=0$ and the crossover point is dominated by zero-mode effects, featuring an explicit dependence on the IR cutoff of the system. For the reduced state of a single oscillator, we show that this crossover occurs in the region $Na{m}_f\sim 𝒪(1)$.

We investigate entanglement of the Hawking radiation in a dispersive model with subluminal dispersion. In this model, feature of the Hawking radiation is represented by three mode Bogoliubov transformation connecting the in-vacuum state and the out-state. We obtain the exact form of the tripartite in-vacuum state which encodes structure of multipartite entanglement. Bogoliubov coefficients are computed by numerical calculation of the wave equation with subluminal dispersion and it is found that genuine tripartite entanglement persists in whole frequency range up to the cutoff arisen from the subluminal dispersion. In the low frequency region, amount of the tripartite entanglement is far small compared to bipartite entanglement between the Hawking particle and its partner mode, and the deviation from the thermal spectrum is negligible. On the other hand, in the high frequency region near the cutoff, entanglement of the system is equally shared by two pairs of three modes, and the thermal nature of the Hawking radiation is lost.

Motivated by the recent progresses in the formulation of geometric theories for the fractional quantum Hall states, we propose a novel nonrelativistic geometric model for the Laughlin states based on an extension of the Nappi-Witten geometry. We show that the U(1) gauge sector responsible for the fractional Hall conductance, the gravitational Chern-Simons action and Wen-Zee term associated to the Hall viscosity can be derived from a single Chern-Simons theory with a gauge connection that takes values in the extended Nappi-Witten algebra. We then provide a new derivation of the chiral boson associated to the gapless edge states from the Wess-Zumino-Witten model that is induced by the Chern-Simons theory on the boundary.

We present a characteristic initial value approach to calculating the Green function of the Regge-Wheeler and Zerilli equations. We combine well-known numerical methods with newly derived initial data to obtain a scheme which can in principle be generalized to any desired order of convergence. We demonstrate the approach with implementations up to sixth order in the grid spacing. By combining the results of our numerical code with late-time tail expansions and methods of subtracting the direct part of the Green function, we show that the scalar self-force in Schwarzschild spacetime can be computed to better accuracy than previous Green function based approaches. We also demonstrate agreement with frequency domain methods for computing the Green function in the gravitational case. Finally, we apply the Regge-Wheeler and Zerilli Green functions to the computation of the gravitational energy flux.

Numerical analysis of a dark matter axionlike cloud in the vicinity of a rotating black hole has been performed. The model where an axionlike scalar field is nontrivially coupled to the Maxwell field is studied in the spacetime of a Kerr black hole in a uniform magnetic field and in the Kerr-Newman one. The dependence of scalar mass and black hole angular momentum on accumulation of the axion dark matter cloud was given. It was revealed that condensation of the dark matter clouds is preferable for a very small mass of axion.

In this paper, we study the spontaneous scalarization of an extended, self-gravitating system which is static, cylindrically symmetric and possesses electromagnetic fields. We demonstrate that a real massive scalar field condenses on this Melvin magnetic universe solution when introducing a nonminimal coupling between the scalar field and (a) the magnetic field and (b) the curvature of the space-time, respectively. We find that in both cases, the solutions exist on a finite interval of the coupling constant and that solutions with a number of nodes $k$ in the scalar field are present. For case (a) we observe that the intervals of existence are mutually exclusive for different $k$.

In generic Friedmann-Lemaître-Robertson-Walker spacetimes, states of low energy (SLEs) are defined to minimize the regularized energy density smeared along the timelike curve of an isotropic observer, which is specified via a smearing function. For every smearing function, SLEs are unique (up to a phase) and are shown to be exact Hadamard states. In this work, we investigate the viability of SLEs as the vacuum for cosmological perturbations in hybrid loop quantum cosmology, motivated by the fact that SLEs have been shown to provide suitable vacua in models where a period of kinetic dominance precedes inflation. We find that there are two classes of smearing functions that can be seen as natural choices within this context, for which the corresponding SLEs and the resulting power spectra at the end of inflation are quite insensitive to the exact shape and support of the smearing function. Furthermore, a preliminary analysis of the tensor-to-scalar ratio and of the spectral index indicates as good an agreement with observations as that of standard cosmology.

We test the statistical isotropy (SI) of the $E$-mode polarization of the cosmic microwave background (CMB) radiation observed by the Planck satellite using two statistics, namely, the $\alpha$ estimator that is derived from the contour Minkowski tensor (CMT), and the directional statistic ($\mathcal{D}$ statistic). The $\alpha$ estimator provides information about the alignment of structures and can be used to infer statistical properties such as Gaussianity and SI of random fields. The $\mathcal{D}$ statistic is based on detecting preferred directionality shown by vectors defined by the field. We compute $\alpha$ and $\mathcal{D}$ statistic for the low resolution component separated SMICA $E$-mode map of CMB polarization, and compare with the values calculated using FFP10 SMICA simulations. We find good agreement between the Planck data and SMICA simulations for both $\alpha$ estimator and $\mathcal{D}$ statistic.