We investigate the thermodynamics of Gauss–Bonnet black holes in asymptotically de Sitter spacetimes embedded in an isothermal cavity, via a Euclidean action approach. We consider both charged and uncharged black holes, working in the extended phase space where the cosmological constant is treated as a thermodynamic pressure. We examine the phase structure of these black holes through their free energy. In the uncharged case, we find both Hawking-Page and small-to-large black hole phase transitions, whose character depends on the sign of the Gauss-Bonnet coupling. In the charged case, we demonstrate the presence of a swallowtube, signaling a compact region in phase space where a small-to-large black hole transition occurs.

Gravitational waves from the explosive merger of distant black holes are encoded with details regarding the complex extreme-gravity spacetime present at their source. Famously described by the Kerr spacetime metric for rotating black holes in general relativity, what if effects beyond this theory are present? One way to efficiently test this hypothesis is to first obtain a metric which parametrically deviates from the Kerr metric in a model-independent way. Given such a metric, one can then predict the ensuing corrections to both the inspiral and ringdown portions of the gravitational waveform for black holes present in the new spacetime. With these tools in hand, one can then test gravitational wave signals for such effects by two different methods, (i) inspiral-merger-ringdown consistency test and (ii) parametrized test. In this paper, we demonstrate the exact recipe one needs to do just this. We first derive parametrized corrections to the waveform inspiral, ringdown, and remnant properties for a generic non-Kerr spacetime and apply this to two examples for beyond-Kerr spacetimes each parametrized by a single non-Kerr parameter. We then predict the beyond-Kerr parameter magnitudes required in an observed gravitational wave signal to be statistically inconsistent with the Kerr case in general relativity. We find that the two methods give very similar bounds. The constraints found with existing gravitational-wave events are comparable to those from x-ray observations, while future gravitational-wave observations using Cosmic Explorer (Laser Interferometer Space Antenna) can improve such bounds by 2 (3) orders of magnitude.

Under the assumption that a dynamical scalar field is responsible for the current acceleration of the Universe, we explore the possibility of probing its physics in black hole merger processes with gravitational wave interferometers. Remaining agnostic about the microscopic physics, we use an effective field theory approach to describe the scalar dynamics. We investigate the case in which some of the higher-derivative operators, that are highly suppressed on cosmological scales, instead become important on typical distances for black holes. If a coupling to the Gauss-Bonnet operator is one of them, a nontrivial background profile for the scalar field can be sourced in the surroundings of the black hole, resulting in a potentially large amount of “hair.” In turn, this can induce sizeable modifications to the spacetime geometry or a mixing between the scalar and the gravitational perturbations. Both effects will ultimately translate into a modification of the quasinormal mode spectrum in a way that is also sensitive to other operators besides the one sourcing the scalar background. The presence of deviations from the predictions of general relativity in the observed spectrum can therefore serve as a window onto dark energy physics.

Euclidean wormholes first appeared in the Euclidean path integral approach to quantum gravity. In a more general way, Hawking and Page interpreted such configurations as solutions to the Wheeler-DeWitt equation with appropriate boundary conditions. We study Euclidean wormholes in the framework of the Hořava-Lifshitz theory of gravity. We use its projectable version to obtain the Wheeler-DeWitt equation of a minisuperspace model considering a closed Friedmann Universe with a massless scalar field. For large values of the scale factor we find that the solution of the Wheeler-DeWitt equation coincides with the one obtained by Hawking. Whereas in the limit corresponding to the early Universe we find a new set of solutions, which agree with the Hawking and Page boundary conditions for wormholes.

The 1965 Penrose singularity theorem demonstrates the utterly inevitable and unavoidable formation of spacetime singularities under physically reasonable assumptions, and it remains one of the main results in our understanding of black holes. It is standard lore that quantum gravitational effects will always tame these singularities in black hole interiors. However, the Penrose’s theorem provides no clue as to the possible (nonsingular) geometries that may be realized in theories beyond general relativity as the result of singularity regularization. In this paper, we analyze this problem in spherically symmetric situations, being completely general otherwise, in particular regarding the dynamics of the gravitational and matter fields. Our main result is that, contrary to what one might expect, the set of regular geometries that arises is remarkably limited. We rederive geometries that have been analyzed before, but also uncover some new possibilities. Moreover, the complete catalog of possibilities that we obtain allows us to draw the novel conclusion that there is a clear tradeoff between internal and external consistency: one has to choose between models that display internal inconsistencies, or models that include significant deviations with respect to general relativity, which should therefore be amenable to observational tests via multimessenger astrophysics.

We propose a novel class of compact dark matter objects in theories where the dark matter consists of multiple sectors. We call these objects $N$-MACHOs. In such theories neither the existence of dark matter species nor their extremely weak coupling to the observable sector represent additional hypotheses but instead are imposed by the solution to the Hierarchy Problem and unitarity. The crucial point is that particles from the same sector have nontrivial interactions but interact only gravitationally otherwise. As a consequence, the pressure that counteracts the gravitational collapse is reduced while the gravitational force remains the same. This results in collapsed structures much lighter and smaller as compared to the ordinary single-sector case. We apply this phenomenon to a dark matter theory that consists of $N$ dilute copies of the Standard Model. The solutions do not rely on an exotic stabilization mechanism, but rather use the same well-understood properties as known stellar structures. This framework also gives rise to new microscopic superheavy structures, for example with mass ${10}^8\mathrm{g}$ and size ${10}^{-13}\mathrm{cm}$. By confronting the resulting objects with observational constraints, we find that, due to a huge suppression factor entering the mass spectrum, these objects evade the strongest constrained region of the parameter space. Finally, we discuss possible formation scenarios of $N$-MACHOs. We argue that, due to the efficient dissipation of energy on small scales, high-density regions such as ultracompact minihalos could serve as formation sites of $N$-MACHOs.

We realize the Agrawal-Obied-Vafa (AOV) swampland proposal of fading dark matter by the model of Salam-Sezgin and its string realization of Cvetič-Gibbons-Pope. The model describes a compactification of 6-dimensional supergravity with a monopole background on a 2-sphere. In 4 dimensions, there are 2 scalar fields, $X$ and $Y$, and the effective potential in the Einstein frame is an exponential with respect to $Y$ times a quadratic polynomial in the field $e^{-X}$. When making the volume of the 2-sphere large, namely for large values of $Y$, there appears a tower of states, which according to the infinite distance swampland conjecture becomes exponentially massless. If the standard model fields are confined on Neveu-Schwarz 5-branes the 6-dimensional gauge couplings are independent of the string dilaton in the string frame, and upon compactification to 4 dimensions the 4-dimensional gauge couplings depend on $X$ (rather than the dilaton $Y$) which is fixed at the minimum of the potential. This avoids direct couplings of the dilaton to matter suppressing extra forces competing with gravity. We show that this set up has the salient features of the AOV models, and ergo can potentially ameliorate the tension between local distance ladder and cosmic microwave background estimates of the Hubble constant $H_0$. Indeed, the tower of string states that emerges from the rolling of $Y$ constitutes a portion of the dark matter, and the way in which the $X$ particle and its Kaluza-Klein excitations evolve over time (refer to as fading dark matter) is responsible for reducing the $H_0$ tension. Although the AOV proposal does not fully resolve the tension in $H_0$ measurements, it provides a dynamical dark energy model of cosmology that satisfies the de Sitter swampland conjecture. We comment on a viable solution to overcome the tension between low- and high-redshift observations within the AOV background and discuss the implications for the swampland program.

We extend the effective field theory of inflation to a general Lagrangian constructed from Arnowitt-Deser-Misner variables that encompasses the most general interactions with up to second derivatives of the scalar field whose background breaks temporal diffeomorphism invariance. Degeneracy conditions, corresponding to 8 distinct types—only one of which corresponds to known degenerate higher-order scalar-tensor models—provide necessary conditions for eliminating the Ostrogradsky ghost in a covariant theory at the level of the quadratic action in unitary gauge. Novel implications of the degenerate higher-order system for the Cauchy problem are illustrated with the phase space portrait of an explicit inflationary example: not all field configurations lead to physical solutions for the metric even for positive potentials; solutions are unique for a given configuration only up to a branch choice; solutions on one branch can apparently end at nonsingular points of the metric and their continuation on alternate branches lead to nonsingular bouncing solutions; unitary gauge perturbations can go unstable even when degenerate terms in the Lagrangian are infinitesimal. The attractor solution leads to an inflationary scenario where slow-roll parameters vary and running of the tilt can be large even with no explicit features in the potential far from the end of inflation, requiring the optimized slow-roll approach for predicting observables.

The velocity of a gravitational wave (GW) source provides crucial information about its formation and evolution processes. Previous studies considered the Doppler effect on the phase of GWs as a potential signature of a time-dependent velocity of the source. However, the Doppler shift only accounts for the time component of the wave vector, and in principle motion also affects the spatial components. The latter effect, known as “aberration” for light, is analyzed in this paper for GWs and applied to the waveform modeling of an accelerating source. We show that the additional aberrational phase shift could be detectable in two astrophysical scenarios, namely, a recoiling binary black hole (BBH) due to GW radiation and a BBH in a triple system. Our results suggest that adding the aberrational phase shift in the waveform templates could significantly enhance the detectability of moving sources.

Jet production and jet substructure modification in heavy-ion collisions have played an essential role in revealing the in-medium evolution of parton showers and the determination of the properties of strongly interacting matter under extreme conditions. It is imperative to extend these studies to include flavor tagging and to devise observables that are sensitive to the partonic origin of jets. The average jet charge, defined as the momentum-weighted sum of the electric charges of particles inside the jet, is a proxy of the electric charge of the quark or gluon that initiates the jet. We demonstrate how the factorization framework of soft-collinear effective theory can be generalized to evaluate the jet charge in a dense strongly interacting matter environment, such as the one produced in nuclear reactions at collider energies. Observables that can separate the contribution of in-medium branching from the trivial isospin effects are identified, and their connection to established jet quenching effects is elucidated. We present predictions for the transverse momentum dependence of the jet charge distribution in nucleus-nucleus collisions and its modification relative to the proton case.

This paper explores the effects of changes in matter density profiles on neutrino oscillation probabilities, and whether these could potentially be seen by the future Hyper-Kamiokande long-baseline oscillation experiment (T2HK). The analysis is extended to include the possibility of having an additional detector in Korea (T2HKK). In both cases, we find that these effects will be immeasurable, as the magnitudes of the changes in the oscillation probabilities induced in all density profile scenarios considered here remain smaller than the estimated experimental sensitivity to the oscillation probabilities of each experiment, for both appearance and disappearance channels. Therefore, we conclude that using a constant density profile is sufficient for both the T2HK and T2HKK experiments.

We consider an asymptotically free vectorial gauge theory, with gauge group $G$ and $N_f$ fermions in a representation $R$ of $G$, having an infrared fixed point of the renormalization group. We calculate scheme-independent series expansions for the anomalous dimensions of higher-spin bilinear fermion operators at this infrared fixed point up to $O({\mathrm{\Delta }}_f^3)$, where ${\mathrm{\Delta }}_f$ is an $N_f$-dependent expansion variable. Our general results are evaluated for several special cases, including the case $G=\mathrm{SU}(N_c)$ with $R$ equal to the fundamental and adjoint representations.

Phenomenological studies of flavored dark matter (FDM) models often have to assume a near-diagonal flavor structure in the coupling matrix in order to remain consistent with bounds from flavor violating processes. In this paper we show that for lepton FDM, such a structure can naturally arise from an extra dimensional setup. The extra dimension is taken to be flat, with the dark matter and mediator fields confined to a brane on one end of the extra dimension, and the Higgs field to a brane on the other end. The Standard Model fermion and gauge fields are the zero modes of corresponding bulk fields with appropriate boundary conditions. Global flavor symmetries exist in the bulk and on the FDM brane, while they are broken on the Higgs brane. Flavor violating processes arise due to the misalignment of bases for which the interactions on the two branes are diagonalized, and their size can be controlled by a choice of the lepton profiles along the extra dimension. By studying the parameter space for the model, we show that when relic abundance and indirect detection constraints are satisfied, the rates for flavor violating processes such as $\mu \to e\gamma$ remain far below the experimental limits.

We leverage recent breakthroughs in neural density estimation to propose a new unsupervised ANOmaly detection with Density Estimation (ANODE) technique. By estimating the conditional probability density of the data in a signal region and in sidebands, and interpolating the latter into the signal region, a fully data-driven likelihood ratio of data versus background can be constructed. This likelihood ratio is broadly sensitive to overdensities in the data that could be due to localized anomalies. In addition, a unique potential benefit of the ANODE method is that the background can be directly estimated using the learned densities. Finally, ANODE is robust against systematic differences between signal region and sidebands, giving it broader applicability than other methods. We demonstrate the power of this new approach using the LHC Olympics 2020 R&D dataset. We show how ANODE can enhance the significance of a dijet bump hunt by up to a factor of 7 with a 10% accuracy on the background prediction. While the LHC is used as the recurring example, the methods developed here have a much broader applicability to anomaly detection in physics and beyond.

We consider the minimal supersymmetric grand unified model based on the group SO(10) and study conditions leading to possible domain wall formation. It has been shown earlier that the supersymmetry preserving vacuum expectation values (vevs) get mapped to distinct but degenerate set of vevs under action of $D$ parity, leading to formation of domain walls as topological pseudodefects. The metastability of such walls can make them relatively long-lived and contradict standard cosmology. Thus, we are led to consider adding a nonrenormalizable Planck scale suppressed operator that breaks SO(10) symmetry but preserves Standard Model symmetry. For a large range of right-handed breaking scales $M_R$, this is shown to give rise to the required pressure difference to remove the domain walls without conflicting with consistent big bang nucleosynthesis while avoiding gravitino overproduction. However, if the walls persist till the onset of weak (thermal) inflation, then a low $\sim 10–100\mathrm{TeV}$ $M_R$ becomes problematic.

There are emerging tensions for theory results of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment both within recent lattice QCD calculations and between some lattice QCD calculations and R-ratio results. In this paper, we work toward scrutinizing critical aspects of these calculations. We focus in particular on a precise calculation of Euclidean position-space windows defined by RBC/UKQCD that are ideal quantities for cross-checks within the lattice community and with R-ratio results. We perform a lattice QCD calculation using physical up, down, strange, and charm sea quark gauge ensembles generated in the staggered formalism by the MILC Collaboration. We study the continuum limit using inverse lattice spacings from $a^{-1}\approx 1.6\mathrm{GeV}$ to 3.5 GeV, identical to recent studies by FNAL/HPQCD/MILC and Aubin et al. and similar to the recent study of BMW. Our calculation exhibits a tension for the particularly interesting window result of $a_{\mu }^{\mathrm{ud},\mathrm{conn}.,\mathrm{isospin},\mathrm{W}}$ from 0.4 to 1.0 fm with previous results obtained with a different discretization of the vector current on the same gauge configurations. Our results may indicate a difficulty related to estimating uncertainties of the continuum extrapolation that deserves further attention. In this work, we also provide results for $a_{\mu }^{\mathrm{ud},\mathrm{conn}.,\mathrm{isospin}}$, $a_{\mu }^{\mathrm{s},\mathrm{conn}.,\mathrm{isospin}}$, $a_{\mu }^{\mathrm{SIB},\mathrm{conn}.}$ for the total contribution and a large set of windows. For the total contribution, we find $a_{\mu }^{\mathrm{HVP}\mathrm{LO}}=714(27)(13){10}^{-10}$, $a_{\mu }^{\mathrm{ud},\mathrm{conn}.,\mathrm{isospin}}=657(26)(12){10}^{-10}$, $a_{\mu }^{\mathrm{s},\mathrm{conn}.,\mathrm{isospin}}=52.83(22)(65){10}^{-10}$, and $a_{\mu }^{\mathrm{SIB},\mathrm{conn}.}=9.0(0.8)(1.2){10}^{-10}$, where the first uncertainty is statistical and the second systematic. We also comment on finite-volume corrections for the strong-isospin-breaking corrections.

We investigate the density fluctuations induced by hadronic interactions at low temperatures and large chemical potentials after the hadronization of quark-gluon plasma (QGP). We analyze the structures of net-baryon number kurtosis and skewness and elaborate on their relations with the nuclear liquid-gas (LG) phase transition and hadronic interactions above the critical temperature. Combining with the relevant experimental projects at RHIC/NICA/FAIR/J-PARC/HIAF with collision energies from 200 GeV to 1.8 GeV, we propose a double-peak structure of kurtosis (skewness) as a function of collision energy, which can be taken to identify the chiral phase transition and the nuclear liquid-gas phase transition. In particular, the fluctuation distributions at low temperatures provide a new method to explore hadronic interactions and nuclear liquid-gas transition.

We study classical and quantum (at large-$N$) field equations of bosonic tensor models with quartic interactions and $O(N{)}^3$ symmetry. Among various possible patterns of spontaneous symmetry breaking we highlight an $SO(3)$ invariant solution, with the tensor field expressed in terms of the Wigner $3jm$ symbol. We argue that such solution has a special role in the large-$N$ limit, as in particular its scaling in $N$ can provide an on-shell justification for the melonic large-$N$ limit of the two-particle irreducible effective action in a broken phase.

It is a well-known property of holographic theories that diffeomorphism invariance in the bulk space-time implies Weyl invariance of the dual holographic field theory in the sense that the field theory couples to a conformal class of background metrics. The usual Fefferman-Graham formalism, which provides us with a holographic dictionary between the two theories, breaks explicitly this symmetry by choosing a specific boundary metric and a corresponding specific metric ansatz in the bulk. In this paper, we show that a simple extension of the Fefferman-Graham formalism allows us to sidestep this explicit breaking; one finds that the geometry of the boundary includes an induced metric and an induced connection on the tangent bundle of the boundary that is a Weyl connection (rather than the more familiar Levi-Civita connection uniquely determined by the induced metric). Properly invoking this boundary geometry has far-reaching consequences: the holographic dictionary extends and naturally encodes Weyl-covariant geometrical data, and, most importantly, the Weyl anomaly gains a clearer geometrical interpretation, cohomologically relating two Weyl-transformed volumes. The boundary theory is enhanced due to the presence of the Weyl current, which participates with the stress tensor in the boundary Ward identity.

We compute the expectation value of the energy-momentum tensor in the in-vacuum state of the quantized Dirac field coupled to a uniform electric field background on the Poincaré patch of the two-dimensional de Sitter spacetime (${\mathrm{dS}}_2$). The adiabatic regularization scheme is applied to remove the ultraviolet divergencies from the expressions. Then we obtain a finite result for the induced energy-momentum tensor that varies continuously under a continuous change of the electric field strength and the Dirac field mass. We find that the off-diagonal components of the induced energy-momentum tensor vanish. The absolute values of the diagonal components increase as the electric field increases and decrease as the Dirac field mass increases except in the very near vicinity of their zero points. We derive the trace anomaly of the induced energy-momentum tensor, which agrees precisely with the trace anomaly derived earlier in the literature. We have discussed the backreaction of the induced energy-momentum tensor on the gravitational field of the ${\mathrm{dS}}_2$.