False vacuum states are metastable in quantum field theories, and true vacuum bubbles can be nucleated due to the quantum tunneling effect. It was recently suggested that an evaporating black hole (BH) can be a catalyst of bubble nucleations and dramatically shortens the lifetime of the false vacuum. In particular, in the context of the Standard Model valid up to a certain energy scale, even a single evaporating BH may spoil the successful cosmology by inducing the decay of our electroweak vacuum. In this paper, we reinterpret catalyzed vacuum decay by BHs, using an effective action for a thin-wall bubble around a BH to clarify the meaning of bounce solutions. We calculate bounce solutions in the limit of a flat spacetime and in the limit of negligible backreaction to the metric, where it is much easier to understand the physical meaning, and compare these results with the full calculations done in the literature. As a result, we give a physical interpretation of the enhancement factor: it is nothing but the probability of producing states with a finite energy. This makes it clear that all the other states such as plasma should also be generated through the same mechanism, and calls for finite density corrections to the tunneling rate, which tend to stabilize the false vacuum. We also clarify that the dominant process is always consistent with the periodicity indicated by the BH Hawking temperature after summing over all possible remnant BH masses or bubble energies, although the periodicity of each bounce solution as a function of a remnant BH can be completely different from the inverse temperature of the system, as mentioned in the previous literature.

Owing to the analogy with the ordinary photons in the visible range of the electromagnetic spectrum, the Glauber theory is generalized to address the quantum coherence of the gauge field fluctuations parametrically amplified during an inflationary stage of expansion. The first and second degrees of quantum coherence of relic photons are then computed beyond the effective horizon defined by the evolution of the susceptibility. In the zero-delay limit, the Hanbury Brown–Twiss correlations exhibit a super-Poissonian statistics which is, however, different from the conventional results of the single-mode approximation customarily employed, in quantum optics, to classify the coherence properties of visible light. While in the case of large-scale curvature perturbations, the degrees of quantum coherence coincide with the naive expectation of the single-mode approximation, the net degree of second-order coherence computed for the relic photons diminishes thanks to the effect of the polarizations. We suggest that the Hanbury Brown–Twiss correlations are probably the only tool to assess the quantum or classical origin of the large-scale magnetic fluctuations and of the corresponding curvature perturbations.

Axions and axionlike particles are a leading model for the dark matter in the Universe; therefore, dark matter halos may be boson stars in the process of collapsing. We examine a class of static boson stars with a nonminimal coupling to gravity. We modify the gravitational density of the boson field to be proportional to an arbitrary power of the modulus of the field, introducing a nonstandard coupling. We find a class of solutions very similar to Newtonian polytropic stars that we denote “quantum polytropes.” These quantum polytropes are supported by a nonlocal quantum pressure and follow an equation very similar to the Lane-Emden equation for classical polytropes. Furthermore, we derive a simple condition on the exponent of the nonlinear gravitational coupling, $\alpha >8/3$, beyond which the equilibrium solutions are unstable.

We study solutions for boson stars in the multiscalar field theory with global symmetry $[U(1){]}^N$. The properties of the boson stars are investigated by the Newtonian approximation with the large coupling limit. Our purpose is to study the models bringing about exotic mass distributions which explain flat rotation curves of galaxies. We propose plausible models in which coupling matrices are associated with various graphs in graph theory.

General relativity’s no-hair theorem states that isolated astrophysical black holes are described by only two numbers: mass and spin. As a consequence, there are strict relationships between the frequency and damping time of the different modes of a perturbed Kerr black hole. Testing the no-hair theorem has been a long-standing goal of gravitational-wave astronomy. The recent detection of gravitational waves from black hole mergers would seem to make such tests imminent. We investigate how constraints on black hole ringdown parameters scale with the loudness of the ringdown signal—subject to the constraint that the postmerger remnant must be allowed to settle into a perturbative, Kerr-like state. In particular, we require that—for a given detector—the gravitational waveform predicted by numerical relativity is indistinguishable from an exponentially damped sine after time $t^{\mathrm{cut}}$. By requiring the postmerger remnant to settle into such a perturbative state, we find that confidence intervals for ringdown parameters do not necessarily shrink with louder signals. In at least some cases, more sensitive measurements probe later times without necessarily providing tighter constraints on ringdown frequencies and damping times. Preliminary investigations are unable to explain this result in terms of a numerical relativity artifact.

We study $T^2/Z_N$ orbifold models with magnetic fluxes. We propose a systematic way to analyze the number of zero-modes and their wave functions by use of modular transformation. Our results are consistent with the previous results, and our approach is more direct and analytical than the previous ones. The index theorem implies that the zero-mode number of the Dirac operator on $T^2$ is equal to the index $M$, which corresponds to the magnetic flux in a certain unit. Our results show that the zero-mode number of the Dirac operator on $T^2/Z_N$ is equal to $\lfloor M/N\rfloor +1$ except one case on the $T^2/Z_3$ orbifold.

We study the chiral Ising, the chiral XY, and the chiral Heisenberg models at four-loop order with the perturbative renormalization group in $4-\epsilon$ dimensions and compute critical exponents for the Gross-Neveu-Yukawa fixed points to order $\mathcal{O}({\epsilon }^4)$. Further, we provide Padé estimates for the correlation length exponent, the boson and fermion anomalous dimension, as well as the leading correction to scaling exponent in $2+1$ dimensions. We also confirm the emergence of supersymmetric field theories at four loops for the chiral Ising and the chiral XY models with $N=1/4$ and $N=1/2$ fermions, respectively. Furthermore, applications of our results relevant to various quantum transitions in the context of Dirac and Weyl semimetals are discussed, including interaction-induced transitions in graphene and surface states of topological insulators.

Vector-boson fusion (VBF) is a clean probe of the electroweak-symmetry breaking (EWSB), which inevitably suffers from some level of contamination due to the gluon fusion (ggF). In addition to the jet variables used in the current experimental analysis, we analyze a few more jet-shape variables defined by the girth and integrated jet shape. Taking $H\to W{W}^{*}\to e\nu \mu \nu$ and $H\to \gamma \gamma$ as examples, we perform the analysis with a new technique of the two-step boosted-decision-tree method, which significantly reduces the contamination of the ggF in the VBF sample, thus, providing a clean environment in probing the EWSB sector.

The recent measurement of $R_{K^{*}}$ is yet another hint of new physics (NP) and supports the idea that it is present in $b\to s{\mu }^{+}{\mu }^{-}$ decays. We perform a combined model-independent and model-dependent analysis in order to deduce properties of this NP. Like others, we find that the NP must obey one of two scenarios: (I) $C_9^{\mu \mu }(\mathrm{NP})<0$ or (II) $C_9^{\mu \mu }(\mathrm{NP})=-C_{10}^{\mu \mu }(\mathrm{NP})<0$. A third scenario, (III) $C_9^{\mu \mu }(\mathrm{NP})=-C_9^{\prime \mu \mu }(\mathrm{NP})$, is rejected largely because it predicts $R_K=1$, in disagreement with experiment. The simplest NP models involve the tree-level exchange of a leptoquark (LQ) or a $Z^{\prime }$ boson. We show that scenario II can arise in LQ or $Z^{\prime }$ models, but scenario I is only possible with a $Z^{\prime }$. Fits to $Z^{\prime }$ models must take into account the additional constraints from $B_s^0\text{−}{\overline{B}}_s^0$ mixing and neutrino trident production. Although the LQs must be heavy, O(TeV), we find that the $Z^{\prime }$ can be light, e.g., $M_{Z^{\prime }}=10\mathrm{GeV}$ or 200 MeV.

The LHCb Collaboration recently observed five narrow ${\mathrm{\Omega }}_c^0$ resonances and measured their masses and widths through the decays ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}_c^{+}{K}^{-}$. Motivated by this discovery, and also by the fact that the ground-state bottom baryon ${\mathrm{\Omega }}_b^{-}$ with spin $1/2$ was already found experimentally, we perform a theoretical investigation of the spin-$1/2$ and spin-$3/2$, ${\mathrm{\Omega }}_b$, baryons by calculating the decay width of their first orbitally and radially excited states to ${\mathrm{\Xi }}_b^0{K}^{-}$. For this purpose, we employ the QCD sum rule method on the light cone by including in the analysis the $K$-meson distribution amplitudes up to twist 4. Obtained analytical expressions are utilized to extract parameters of these decay processes, which may be useful for forthcoming experimental studies of bottom baryons.

We show that the experimental data of midrapidity $p_T$ spectra for $p$, $\mathrm{\Lambda }$, $\mathrm{\Xi }$, ${\mathrm{\Omega }}^{-}$, ${\mathrm{K}(892)}^{*0}$, and $\mathrm{\Xi }(1530{)}^{*0}$ in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ can be well fitted by the quark combination mechanism with the parametrized up(down) quark spectrum and strange quark spectrum at hadronization. The averaged transverse momentum $⟨p_T⟩$ and spectrum ratios such as $\mathrm{\Xi }/\mathrm{\Lambda }$ and $\mathrm{\Omega }/\varphi$ calculated from quark combination reproduce the data quite well. The available data of hadronic $p_T$ spectra released by ALICE collaboration in the first three high-multiplicity classes of $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ are also well fitted. The extracted quark spectra at hadronization exhibit a dependence on the multiplicity class and also show a certain similarity to those obtained in $p\text{−}\mathrm{Pb}$ collisions at LHC and in relativistic heavy ion collisions. We make predictions for other hadrons, and propose two scaling behaviors among decuplet baryons and vector mesons as the effective probe of hadron production mechanism at such high collision energies.

We investigate the viscosities of the quark-gluon plasma in strong magnetic fields within the leading-log and lowest Landau level (LLL) approximations. We first show that the bulk viscosity in the direction parallel to the magnetic field is the only component that has a contribution from the quarks occupying the LLL. We then compute the bulk viscosity from the Kubo formula and find an intriguing quark-mass dependence as a consequence of a competition between the suppression of the bulk viscosity by conformal symmetry and an enhancement of the mean-free path by chirality conservation, which governs the behavior in the massless limit. The quark contribution to the viscosity along the magnetic field becomes larger than the one in the absence of a magnetic field. We also briefly estimate the other transport coefficients by considering the contribution of gluons. We show that the shear viscosities are suppressed compared to their values in the absence of a magnetic field.

We describe the Mott dissociation of pions and kaons within a Beth-Uhlenbeck approach based on the Polyakov-loop improved Nambu–Jona-Lasinio model, which allows for a unified description of bound, resonant and scattering states. Within this model we evaluate the temperature and chemical potential dependent modification of the phase shifts both in the pseudoscalar and scalar isovector meson channels for $N_f=2+1$ quark flavors. We show that the character change of the pseudoscalar bound states to resonances in the continuum at the Mott transition temperature is signaled by a jump of the phase shift at the threshold from $\pi$ to zero, in accordance with the Levinson theorem. In particular, we demonstrate the importance of accounting for the scattering continuum states, which ensures that the total phase shift in each of the meson channels vanishes at high energies, thus eliminating mesonic correlations from the thermodynamics at high temperatures. In this way, we prove that the present approach provides a unified description of the transition from a meson gas to a quark-gluon plasma. We discuss the occurrence of an anomalous mode for mesons composed of quarks with unequal masses which is particularly pronounced for $K^{+}$ and ${\kappa }^{+}$ states at finite densities a a possible mechanism to explain the “horn” effect for the $K^{+}/{\pi }^{+}$ ratio in heavy-ion collisions.

Following Verlinde’s recent heuristic construction or emergent gravity, Hossenfelder wrote down the Lagrangian capturing some aspects of this theory. We point out that there is an error in calculations whose consequence is that a cosmological de Sitter space solution is not recovered from this Lagrangian. We correct this error in order to obtain the desired solution. We also show that small perturbations around the de Sitter space grow, which implies that this state is not stable. However, the presence of matter and radiation might, in principle, provide stability.

We consider double-winding, triple-winding, and multiple-winding Wilson loops in the $SU(N)$ Yang-Mills gauge theory. We examine how the area-law falloff of the vacuum expectation value of a multiple-winding Wilson loop depends on the number of color $N$. In sharp contrast to the difference-of-areas law recently found for a double-winding $SU(2)$ Wilson loop average, we show irrespective of the spacetime dimensionality that a double-winding $SU(3)$ Wilson loop follows a novel area law which is neither difference-of-areas nor sum-of-areas law for the area-law falloff and that the difference-of-areas law is excluded and the sum-of-areas law is allowed for $SU(N)$ ($N\ge 4$), provided that the string tension obeys the Casimir scaling for the higher representations. Moreover, we extend these results to arbitrary multiple-winding Wilson loops. Next, we argue that the area law follows a novel law, which is neither sum-of-areas nor difference-of-areas law when $N\ge 3$. In fact, such a behavior is exactly derived in the $SU(N)$ Yang-Mills theory in the two-dimensional spacetime. Finally, we introduce new Wilson loops whose averages are expected to follow the difference-of-areas law even in the $SU(N)$ Yang-Mills theory for $N\ge 3$.

Using scaling arguments and the property of self-similarity we derive the Casimir energies of Sierpinski triangles and Sierpinski rectangles. The Hausdorff-Besicovitch dimension (fractal dimension) of the Casimir energy is introduced and the Berry-Weyl conjecture is discussed for these geometries. We propose that for a class of fractals, comprising compartmentalized cavities, it is possible to establish a finite value to the Casimir energy even while the Casimir energy of the individual cavities consists of divergent terms.

We show that the exact solution of Einstein’s equations describing a binary system of aligned identical Kerr black holes separated by a massless strut follows straightforwardly from the extended 2-soliton solution possessing equatorial symmetry. We give its concise analytic form in terms of physical parameters and then compare with our old solution of that problem obtained in canonical parametrization, demonstrating the equivalence of the two approaches. A surprising physical by-product of our analysis is the discovery that up to three different configurations of two corotating Kerr sources can have equal masses and equal angular momenta. We also introduce physical parametrization to the general six-parameter asymmetric configuration which permits to treat analytically the case of two nonequal corotating black holes.

We describe a multivariate classifier for candidate events in a templated search for gravitational-wave (GW) inspiral signals from neutron-star–black-hole (NS-BH) binaries, in data from ground-based detectors where sensitivity is limited by non-Gaussian noise transients. The standard signal-to-noise ratio (SNR) and chi-squared test for inspiral searches use only properties of a single matched filter at the time of an event; instead, we propose a classifier using features derived from a bank of inspiral templates around the time of each event, and also from a search using approximate sine-Gaussian templates. The classifier thus extracts additional information from strain data to discriminate inspiral signals from noise transients. We evaluate a random forest classifier on a set of single-detector events obtained from realistic simulated advanced LIGO data, using simulated NS-BH signals added to the data. The new classifier detects a factor of 1.5–2 more signals at low false positive rates as compared to the standard “reweighted SNR” statistic, and does not require the chi-squared test to be computed. Conversely, if only the SNR and chi-squared values of single-detector events are available, random forest classification performs nearly identically to the reweighted SNR.