We compute one-loop free energy for $D=4$ Vasiliev higher spin gravities based on Konstein-Vasiliev algebras $hu(m;n|4)$, $ho(m;n|4)$, or $husp(m;n|4)$ and subject to higher spin-preserving boundary conditions, which are conjectured to be dual to the $U(N)$, $O(N)$ or $USp(N)$ singlet sectors, respectively, of free conformal field theories (CFTs) on the boundary of ${\mathrm{AdS}}_4$. Ordinary supersymmetric higher spin theories appear as special cases of Konstein-Vasiliev theories, when the corresponding higher spin algebra contains $OSp(\mathcal{N}|4)$ as a subalgebra. In ${\mathrm{AdS}}_4$ with an $S^3$ boundary, we use a regularization scheme for individual spins that employs their character such that the subsequent sum over all spins is finite, thereby avoiding the need for additional regularization. We find that the contribution of the infinite tower of bulk fermions vanishes. As a result, the free energy is the sum of those which arise in type A and type B models with internal symmetries, the known mismatch between the bulk and boundary free energies for type B model persists, and ordinary supersymmetric higher spin theories exhibit the mismatch as well. The only models that have a match are type A models with internal symmetries, corresponding to $n=0$. The matching requires identification of the inverse Newton constant $G_N^{-1}$ with $N$ plus a proper integer as was found previously for special cases. In ${\mathrm{AdS}}_4$ with an $S^1\times S^2$ boundary, the bulk one-loop free energies match those of the dual free CFTs for arbitrary $m$ and $n$. We also show that a supersymmetric double-trace deformation of free CFT based on $OSp(1|4)$ does not contribute to the $\mathcal{O}(N^0)$ free energy, as expected from the bulk.

We consider finite charge density geometries which interpolate between ${\mathrm{AdS}}_2\times {\mathbb{R}}^2$ in the infrared and ${\mathrm{AdS}}_4$ in the ultraviolet, while traversing an intermediate regime of anisotropic Lifshitz scaling and hyperscaling violation. We work with Einstein-Maxwell-dilaton models and only turn on a background electric field. The spatially modulated instabilities of the near-horizon ${\mathrm{AdS}}_2$ part of the geometry are used to argue that the scaling solutions themselves should be thought of as being unstable—in the deep infrared—to spatially modulated phases. We identify instability windows for the scaling exponents $z$ and $\theta$, which are refined further by requiring the solutions to satisfy the null energy condition. This analysis reinforces the idea that, for large classes of models, spatially modulated phases describe the ground state of hyperscaling violating scaling geometries.

The present work contributes to the study of nonequilibrium aspects of the Casimir forces with the introduction of squeezed states in the calculations. Throughout this article two main results can be found, being both strongly correlated. Primarily, the more formal result involves the development of a first-principles canonical quantization formalism to study the quantum vacuum in the presence of different dissipative material bodies in completely general scenarios. For this purpose, we consider a one-dimensional quantum scalar field interacting with the volume elements’ degrees of freedom of the material bodies, which are modeled as a set of composite systems consisting of quantum harmonic oscillators interacting with an environment (provided as an infinite set of quantum harmonic oscillators acting as a thermal bath). Solving the full dynamics of the composite system through its Heisenberg equations, we study each contribution to the field operator by employing general properties of the Green function. We deduce the long-time limit of the contributions to the field operator. In agreement with previous works, we show that the expectation values of the components of the energy-momentum tensor present two contributions, one associated to the thermal baths and the other one associated to the field’s initial conditions. This allows the direct study of steady situations involving different initial states for the field (keeping arbitrary thermal states for the baths). This leads to the other main result, consisting of computing the Casimir force when the field is initially in thermal or continuum-single-mode squeezed states (the latter being characterized by a given bandwidth and frequency). Time averaging is required for the squeezed case, showing that both results can be given in a unified way, while for the thermal state, all the well-known equilibrium results can be successfully reproduced. Finally, we compared the initial conditions’ contribution and the total force for each case, showing that the latter can be tuned in a wide range of values through varying the size of the bandwidth.

We consider a model belonging to the class of gravities with dynamical torsion. The model is free of ghosts and gradient instabilities about Minkowski and torsionless Einstein backgrounds. We find that at zero cosmological constant, the model admits a self-accelerating solution with a non-Riemannian connection. Small value of the effective cosmological constant is obtained at the expense of the hierarchy between the dimensionless couplings.

So far, direct detection searches have come up empty handed in their quest for dark matter (DM). Meanwhile, asteroseismology arises as a complementary tool to study DM, as its accumulation in a star can enhance energy transport by providing a conduction mechanism, producing significant changes in the stellar structure during the course of the star’s evolution. The stellar core, particularly affected by the presence of DM, can be investigated through precise asteroseismic diagnostics. We modeled three stars including DM energy transport: the Sun; a slightly less massive and much older star, KIC 7871531 ($0.85M_{\odot }$, 9.41 Gyr); and a more massive and younger one, KIC 8379927 ($1.12M_{\odot }$, 1.82 Gyr). We considered both the case of weakly interactive massive particles, albeit with a low annihilation, and the case of asymmetric DM for which the number of trapped particles in the star can be much greater. By analyzing these models with asteroseismic separation ratios weighted towards the core, we found indications limiting the effective spin-dependent DM-proton coupling for masses of a few GeV. This independent result is very close to the most recent and most stringent direct detection DM constraints.

The recent discovery of gravitational waves from merging black holes has generated interest in primordial black holes as a possible component of dark matter. In this paper, we show that pulsar timing may soon have sufficient data to constrain $1–1000M_{\odot }$ primordial black holes (PBHs) via the nondetection of a third-order Shapiro time delay as the black holes move around the Galactic halo. We present the results of a Monte Carlo simulation which suggests that future data from known pulsars may be capable of constraining the PBH density more stringently than other existing methods in the mass range $\sim 1–30M_{\odot }$. We find that timing new pulsars discovered using the proposed Square Kilometre Array may constrain primordial black holes in this mass range to comprise less than $\sim 1\%–10\%$ of the dark matter.

A deep connection has been recently established between soft theorems and symmetries at null infinity in gravity and gauge theories, recasting the former as Ward identities of the latter. In particular, different orders (in the frequency of the soft particle) in the soft theorems are believed to be controlled by different asymptotic symmetries. In this paper we argue that this need not be the case by focusing on the soft photon theorem. We argue that the subleading soft factor follows from the same symmetry responsible for the leading one, namely certain residual (large) gauge transformations of the gauge theory. In particular, expanding the associated charge in inverse powers of the radial coordinate, the (sub)leading charge yields the (sub)leading soft factor.

The observation of a protophobic 16.7 MeV vector boson has been reported by a ${}^8\mathrm{Be}$ nuclear transition experiment. Such a new particle could mediate between the Standard Model and a dark sector, which includes the dark matter. In this paper, we show some simple models of the dark matter which satisfy the thermal relic abundance under the current experimental bounds from the direct and the indirect detections. In a model, it is found that an appropriate self-scattering cross section to solve the small scale structure puzzles can be achieved.

The Kalb-Ramond field, identifiable with bulk torsion in a five-dimensional Randall Sundrum (RS) scenario, has Chern-Simons interactions with gauge bosons, from the requirement of gauge anomaly cancellation. Its lowest Kaluza Klein (KK) mode on the visible 3-brane can be identified with a spin-0 $CP$-odd field, namely, the axion. By virtue of the warped geometry and Chern-Simons couplings, this axion has unsuppressed interactions with gauge bosons in contrast to ultra-suppressed interactions with fermions. The ensuing dynamics can lead to a peak in the diphoton spectrum, which could be observed at the LHC, subject to the prominence of the signal. Moreover, the results can be numerically justified when the warp factor is precisely in the range required for stabilization of the electroweak scale.

We construct the three-flavor Lorentz-invariant meson-baryon chiral Lagrangians at the order $p^4$, with which a full one-loop investigation may be performed. One obtains 540 independent terms. The processes with the minimal number of mesons and photons to which this order of Lagrangians may contribute are also presented.

It is possible to find initial states for gravitational collapse whose entropy approximately saturates the Bekenstein-Hawking entropy of the final black hole. The prototypical example of such a state is that envisaged by Zurek and Thorne, and also by Susskind: for a black hole of mass $M$, a number $\sim M^2$ of quanta with energies of order $\sim M^{-1}$ are accreted on a time scale of order $\sim M^3$, an approximate time-reverse of Hawking evaporation. There is lore that all initial states which saturate the Bekenstein-Hawking entropy must involve a formation time scale of this order, $\sim M^3$, and not the much shorter dynamical time scale $\sim M$. Counterexamples to this lore have been found by Sorkin, Wald and Zhang, and also by Hsu and Reeb, in the form of semiclassical initial data sets. However, the spacetimes that correspond to these counterexamples possess white holes in the past, as well as black holes in the future, which casts doubt on their physical relevance. We modify the counterexamples to eliminate the white holes, yielding formation time scales of order $\sim M^2$, and argue that the lore is unfounded.

We present a calculation of the decay rate of the electroweak vacuum, fully including all gravitational effects and a possible nonminimal Higgs-curvature coupling $\xi$, and using the three-loop Standard Model effective potential. Without a nonminimal coupling, we find that the effect of the gravitational backreaction is small and less significant than previous calculations suggested. The gravitational effects are smallest, and almost completely suppressed, near the conformal value $\xi =1/6$ of the nonminimal coupling. Moving $\xi$ away from this value in either direction universally suppresses the decay rate.

We continue the presentation of the pragmatic mode-sum regularization (PMR) method for computing the renormalized stress-energy tensor (RSET). We show in detail how to employ the $t$-splitting variant of the method, which was first presented for ${⟨{\varphi }^2⟩}_{\text{ren}}$, to compute the RSET in a stationary, asymptotically flat background. This variant of the PMR method was recently used to compute the RSET for an evaporating spinning black hole. As an example for regularization, we demonstrate here the computation of the RSET for a minimally coupled, massless scalar field on Schwarzschild background in all three vacuum states. We discuss future work and possible improvements of the regularization schemes in the PMR method.

Following an intriguing heuristic argument of Bekenstein, many researches have suggested during the last four decades that quantized black holes may be characterized by discrete radiation spectra. Bekenstein and Mukhanov (BM) have further argued that the emission spectra of quantized ($3+1$)-dimensional Schwarzschild black holes are expected to be sharp in the sense that the characteristic natural broadening $\delta \omega$ of the black-hole radiation lines, as deduced from the quantum time-energy uncertainty principle, is expected to be much smaller than the characteristic frequency spacing $\mathrm{\Delta }\omega =O(T_{\mathrm{BH}}/\hslash )$ between adjacent black-hole quantum emission lines. It is of considerable physical interest to test the general validity of the interesting conclusion reached by BM regarding the sharpness of the Schwarzschild black-hole quantum radiation spectra. To this end, in the present paper we explore the physical properties of the expected radiation spectra of quantized ($D+1$)-dimensional Schwarzschild black holes. In particular, we analyze the functional dependence of the characteristic dimensionless ratio $\zeta (D)\equiv \delta \omega /\mathrm{\Delta }\omega$ on the number $D+1$ of spacetime dimensions. Interestingly, it is proved that the dimensionless physical parameter $\zeta (D)$, which characterizes the sharpness of the black-hole quantum emission spectra, is an increasing function of $D$. In particular, we prove that the quantum emission lines of ($D+1$)-dimensional Schwarzschild black holes in the regime $D\gtrsim 10$ are characterized by the dimensionless ratio $\zeta (D)\gtrsim 1$ and are therefore effectively blended together. The results presented in this paper thus suggest that, even if the underlying energy spectra of quantized ($D+1$)-dimensional Schwarzschild black holes are fundamentally discrete, as argued by many authors, the quantum phenomenon of natural broadening is expected to smear the characteristic emission spectra of these higher-dimensional black holes into a continuum.

We consider, in the context of a braneworld cosmology, the motion of the Universe coupled to a four-form gauge field, with constant field strength, defined in higher dimensions. It is found, under rather general initial conditions, that in this situation there is a period of exponential inflation combined with cyclotron motion in the inflaton field space. The main effect of the cyclotron motion is that slow roll conditions on the inflaton potential, which are typically necessary for exponential inflation, can be evaded. There are Landau levels associated with the four-form gauge field, and these correspond to quantum excitations of the inflaton field satisfying unconventional dispersion relations.

We forecast the future constraints on scale-dependent parametrizations of galaxy bias and their impact on the estimate of cosmological parameters from the power spectrum of galaxies measured in a spectroscopic redshift survey. For the latter we assume a wide survey at relatively large redshifts, similar to the planned Euclid survey, as the baseline for future experiments. To assess the impact of the bias we perform a Fisher matrix analysis, and we adopt two different parametrizations of scale-dependent bias. The fiducial models for galaxy bias are calibrated using mock catalogs of $\mathrm{H}\alpha$ emitting galaxies mimicking the expected properties of the objects that will be targeted by the Euclid survey. In our analysis we have obtained two main results. First of all, allowing for a scale-dependent bias does not significantly increase the errors on the other cosmological parameters apart from the rms amplitude of density fluctuations, ${\sigma }_8$, and the growth index $\gamma$, whose uncertainties increase by a factor up to 2, depending on the bias model adopted. Second, we find that the accuracy in the linear bias parameter $b_0$ can be estimated to within 1%–2% at various redshifts regardless of the fiducial model. The nonlinear bias parameters have significantly large errors that depend on the model adopted. Despite this, in the more realistic scenarios departures from the simple linear bias prescription can be detected with a $\sim 2\sigma$ significance at each redshift explored. Finally, we use the Fisher matrix formalism to assess the impact od assuming an incorrect bias model and find that the systematic errors induced on the cosmological parameters are similar or even larger than the statistical ones.

In modern high precision optical instruments, such as in gravitational wave detectors or frequency references, thermally induced fluctuations in the reflective coatings can be a limiting noise source. This noise, known as coating thermal noise, can be reduced by choosing materials with low mechanical loss. Examination of new materials becomes a necessity in order to further minimize the coating thermal noise and thus improve sensitivity of next generation instruments. We present a novel approach to directly measure coating thermal noise using a high finesse folded cavity in which multiple Hermite-Gaussian modes coresonate. This method is used to probe surface fluctuations on the order ${10}^{-17}\mathrm{m}/\sqrt{\mathrm{Hz}}$ in the frequency range 30–400 Hz. We applied this technique to measure thermal noise and loss angle of the coating used in Advanced LIGO.

After the discovery of the Higgs boson and the rather precise measurement of all electroweak boson’s masses the local structure of the electroweak symmetry breaking potential is already quite well established. However, despite being a key ingredient to a fundamental understanding of the underlying mechanism of electroweak symmetry breaking, the global structure of the electroweak potential remains entirely unknown. The existence of sphalerons, unstable solutions of the classical action of motion that are interpolating between topologically distinct vacua, is a direct consequence of the Standard Model’s $\mathrm{SU}(2{)}_L$ gauge group. Nevertheless, the sphaleron energy depends on the shape of the Higgs potential away from the minimum and can therefore be a litmus test for its global structure. Focusing on two scenarios, the minimal composite Higgs model $\mathrm{SO}(5)/\mathrm{SO}(4)$ or an elementary Higgs with a deformed electroweak potential, we calculate the change of the sphaleron energy compared to the Standard Model prediction. We find that the sphaleron energy would have to be measured to $\mathcal{O}(10)\%$ accuracy to exclude sizeable global deviations from the Standard Model Higgs potential. We further find that because of the periodicity of the scalar potential in composite Higgs models a second sphaleron branch with larger energy arises.