We consider a scenario where the scalaron of $f(\mathcal{R})$ models is related to the volume modulus of string compactifications leaving only one scalar degree of freedom at low energy. The coefficient of the leading curvature squared contribution to the low-energy effective action of gravity determines the mass of the scalaron. We impose that this mass is small enough to allow for the scalaron to drive Starobinski’s inflation. After inflation, the renormalization group evolution of the couplings of the $f(\mathcal{R})$ theory, viewed as a scalar-tensor theory, provides the link with the infrared regime. We consider a scenario where the corrections to the mass of the scalaron are large and reduce it below the electron mass in the infrared, so that the scalaron plays a central role in the low-energy dynamics of the Universe. In particular this leads to a connection between the scalaron mass and the measured vacuum energy provided its renormalization group running at energies higher than the electron mass never drops below the present day value of the dark energy.

The concept of horizon brightened acceleration radiation (HBAR) has brought to us a distinct mechanism of particle production in curved spacetime. In this manuscript we examine the HBAR phenomena for a braneworld black hole (BBH) which emerges as an effective theory in our ($3+1$) dimensional universe due to the higher dimensional gravitational effects. Despite being somewhat similar to the Reissner-Nordström solution in general relativity, the BBH is unique with respect to its charge term which is rather the tidal charge. In this background, we study the transition probability of the atom due to the atom-field interaction and the associated HBAR entropy. Both the quantities acquire modifications over the standard Schwarzschild results and turn out to be the function of the tidal charge. This modifications appear solely due to the bulk gravitational effects as induced on the 3-brane. Studying the Wien’s displacement, we observe an important feature that the wavelengths of HBAR corresponding to the Schwarzschild and the BBH, deviate from each other depending on their masses. This deviation is found to be more pronounced for the mass values slightly greater or comparable to the Planck mass.

The shapes of galaxies trace scalar physics in the late-Universe through the large-scale gravitational potential. Are they also sensitive to higher-spin physics? We present a general study into the observational consequences of vector and tensor modes in the early and late Universe, through the statistics of cosmic shear and its higher-order generalization, flexion. Higher-spin contributions arise from both gravitational lensing and intrinsic alignments, and we give the leading-order correlators for each (some of which have been previously derived), in addition to their flat-sky limits. In particular, we find nontrivial sourcing of shear $EB$ and $BB$ spectra, depending on the parity properties of the source. We consider two sources of vector and tensor modes: scale-invariant primordial fluctuations and cosmic strings, forecasting the detectability of each for upcoming surveys. Shear is found to be a powerful probe of cosmic strings, primarily through the continual sourcing of vector modes; flexion adds little to the constraining power except on very small scales ($\ell \gtrsim 1000$), though it could be an intriguing probe of as-yet-unknown rank-three tensors or halo-scale physics. Such probes could be used to constrain new physics proposed to explain recent pulsar timing array observations.

We examine which first order phase transitions are consistent with today’s astrophysical constraints. In particular, we explore how a well-constrained mass-radius data point would restrict the admissible parameter space and to this end, we employ the most likely candidates of the recent NICER limits of PSR $\mathrm{J}0030+0451$. To systematically vary the stiffness of the equation of state, we employ a parametrizable relativistic mean field equation of state, which is in compliance with results from chiral effective field theory. We model phase transitions via Maxwell constructions and parametrize them by means of the transitional pressure $p_{\text{trans}}$ and the jump in energy density $\mathrm{\Delta }\epsilon$. This provides us with a generic setup that allows for rather general conclusions to be drawn. We outline some regions in the $p_{\text{trans}}\text{−}\mathrm{\Delta }\epsilon$ parameter space that may allow for a phase transition identification in the near future. We also find that a strongly constrained data point, at either exceptionally large or small radii, would reduce the parameter space to such an extent that mass and radius become insufficient indicators of a phase transition.

This paper investigates the transverse Ising model on a discretization of two-dimensional anti–de Sitter space. We use classical and quantum algorithms to simulate real-time evolution and measure out-of-time-ordered correlators (OTOC). The latter can probe thermalization and scrambling of quantum information under time evolution. We compared tensor network-based methods both with simulation on gate-based superconducting quantum devices and analog quantum simulation using Rydberg arrays. While studying this system’s thermalization properties, we observed different regimes depending on the radius of curvature of the space. In particular, we find a region of parameter space where the thermalization time depends only logarithmically on the number of degrees of freedom.

In this work, we investigate the gluon distribution functions for the pion and kaon, in addition to the improved result of the valence-quark ones, in the gauge-invariant nonlocal chiral-quark model, in which the momentum dependence of the quark interactions is properly taken into account. We then analyze the gluon distribution functions, generated dynamically through the splitting functions in the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi QCD evolution. By comparing with the recent lattice QCD results and Jefferson Lab angular momentum global analyses, it is found that the present numerical results for the gluon parton distribution functions for the pion exhibit a good agreement and the valence up-quark distribution results for the pion by reproducing the reanalyzed experimental data with a remarkable agreement. Our prediction on the gluon distribution functions for the kaon is also consistent with the recent lattice data for the kaon within the errors.

Based on $4.5{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data accumulated at center-of-mass energies between 4599.53 and 4698.82 MeV with the BESIII detector, the decay ${\mathrm{\Lambda }}_c^{+}\to n{K}_S^0{\pi }^{+}{\pi }^0$ is observed for the first time with a significance of $9.2\sigma$. The branching fraction is measured to be $(0.85\pm 0.13\pm 0.03)\%$, where the first uncertainty is statistical and the second is systematic, which differs from the theoretical prediction based on isospin by $4.4\sigma$. This indicates that there may be resonant contributions or some unknown dynamics in this decay.

An amplitude analysis of the $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$ decay is presented. The analysis is based on data collected by the LHCb experiment from proton-proton collisions at $\sqrt{s}=7$, 8 and 13 TeV, corresponding to an integrated luminosity of $4.7{\mathrm{fb}}^{-1}$. For the first time, Wilson coefficients and nonlocal hadronic contributions are accessed directly from the unbinned data, where the latter are parametrized as a function of $q^2$ with a polynomial expansion. Wilson coefficients and nonlocal hadronic parameters are determined under two alternative hypotheses: the first relies on experimental information alone, while the second one includes information from theoretical predictions for the nonlocal contributions. Both models obtain similar results for the parameters of interest. The overall level of compatibility with the Standard Model is evaluated to be between 1.8 and 1.9 standard deviations when looking at the ${\mathcal{C}}_9$ Wilson coefficient alone, and between 1.3 and 1.4 standard deviations when considering the full set of ${\mathcal{C}}_9,{\mathcal{C}}_{10},{\mathcal{C}}_9^{\prime }$ and ${\mathcal{C}}_{10}^{\prime }$ Wilson coefficients. The ranges reflect the theoretical assumptions made in the analysis.

We consider correlation functions in 6D (2,0) theories of two $\frac{1}{2}$-Bogomol’nyi-Prasad-Sommerfield (BPS) operators inserted away from a $\frac{1}{2}$-BPS surface defect. In the large central-charge limit the leading connected contribution corresponds to sums of tree-level Witten diagram in ${\mathrm{AdS}}_7\times {\mathrm{S}}^4$ in the presence of an ${\mathrm{AdS}}_3$ defect. We show that these correlators can be uniquely determined by imposing only superconformal symmetry and consistency conditions, eschewing the details of the complicated effective Lagrangian. We explicitly compute all such two-point functions. The result exhibits remarkable hidden simplicity.

There may exist stellar-mass binary black holes (BBH) which merge while orbiting nearby a supermassive black hole (SMBH). In such a triple system, the SMBH will modulate the gravitational waveform of the BBH through orbital Doppler shift and de Sitter precession of the angular momentum. Future space-based gravitational wave (GW) observatories focused on the milli- and decihertz band will be uniquely poised to observe these waveform modulations, as the GW frequency from stellar-mass BBHs varies slowly in this band while modulation effects accumulate. In this work, we apply the Fisher information matrix formalism to estimate how well space-borne GW detectors can measure properties of $\mathrm{BBH}+\mathrm{SMBH}$ hierarchical triples using the GW from orbiting BBH. We extend previous work by considering the more realistic case of an eccentric orbit around the SMBH, and notably include the effects of orbital pericenter precession. We find that for detector concepts such as LISA, B-DECIGO, and TianGO, we can extract the SMBH mass and semimajor axis of the orbit with a fractional uncertainty below the 0.1% level over a wide range of triple system parameters. Furthermore, we find that the effects of pericenter precession and orbital eccentricity significantly improve our ability to measure this system. We also find that while LISA could measure these systems, the decihertz detector concepts B-DECIGO and TianGO would enable better sensitivity to the triple’s parameters.

Ultracold neutrons are great experimental tools to explore the gravitational interaction in the regime of quantized states. From a theoretical perspective, starting from a Dirac equation in curved spacetime, we applied a perturbative scheme to systematically derive the nonrelativistic Schrödinger equation that governs the evolution of the neutron’s wave function in the Earth’s gravitational field. At the lowest order, this procedure reproduces a Schrödinger system affected by a linear Newtonian potential, but corrections due to both curvature and relativistic effects are present. Here, we argue that one should be very careful when going one step further in the perturbative expansion. Proceeding methodically with the help of the Foldy-Wouthuysen transformation and a formal post-Newtonian $1/c^2$ expansion, we derive the nonrelativistic Hamiltonian for a generic static spacetime. By employing Fermi coordinates within this framework, we calculate the next-to-leading-order corrections to the neutron’s energy spectrum. Finally, we evaluate them for typical experimental configurations, such as that of qBounce, and note that, while the current precision for observations of ultracold neutrons may not yet enable to probe them, they could still be relevant in the future or in alternative circumstances.

The black hole no-short hair theorem establishes a universal lower bound on the extension of hairs outside any 4-dimensional spherically symmetric black hole solutions. We generalize this theorem beyond spherical symmetry, specifically for static, axisymmetric hairy black hole solutions and prove that the “hairosphere” must extend beyond the radial extent of the innermost light ring.

The strong cosmic censorship conjecture, which states that the evolution of generic initial data will always produce a globally hyperbolic spacetime, is difficult to test by astronomical observations. In this paper, we study the appearance of the regular black hole without mass inflation, which violates the strong cosmic censorship conjecture. Since the inner horizon is stable, the photons entering the two horizons of the regular black hole in the preceding companion universe can come out from the white hole in our Universe. These rays create a novel multi-ring structure, which is significantly different from the image of the Schwarzschild black hole. This serves a potential method to test the strong cosmic censorship conjecture.

In this study, we investigate the real-time dynamics during the spontaneous deformation of an unstable spherical black hole in asymptotically anti–de Sitter (AdS) spacetime. For the initial value, the static solutions with spherical symmetry are obtained numerically, revealing the presence of a spinodal region in the phase diagram. From the linear stability analysis, we find that only the central part of such a thermodynamically unstable spinodal region leads to the emergence of a type of axial instability. To trigger the dynamical instability, an axial perturbation is imposed on the scalar field. As a result, by the fully nonlinear dynamical simulation, the spherical symmetry of the gravitational system is broken spontaneously, leading to the formation of an axisymmetric black hole.

Spin-induced quadrupole moments provide an important characterization of compact objects, such as black holes, neutron stars and black hole mimickers inspired by additional fields and/or modified theories of gravity. Black holes in general relativity have a specific spin-induced quadrupole moment, with other objects potentially having differing values. Different values of this quadrupole moment lead to modifications of the spin precession dynamics, and consequently modifications to the inspiral waveform. Based on the spin-dynamics and the associated precessing waveform developed in our previous work, we assess the prospects of measuring spin-induced moments in various black hole, neutron star, and BH mimicker binaries. We focus on binaries in which at least one of the objects is in the mass gap (similar to the $2.6M_{\odot }$ object found in GW190814). We find that for generic precessing binaries, the effect of the spin-induced quadrupole moments on the precession is sensitive to the nature of the mass-gap object, i.e., whether it is a light black hole or a massive neutron star, so that this is a good probe of the nature of these objects. For precessing BH mimicker binaries, this waveform also provides significantly tighter constraints on their spin-induced quadrupole moments than the previous results obtained without incorporating the precession effects of spin-induced quadrupole moments. We apply the waveform to sample events in GWTC catalogs to obtain better constraints on the spin-induced quadrupole moments, and discuss the measurement prospects for events in the O4 run of the LIGO-Virgo-KAGRA Collaboration.

The electromagnetic radiation emitted by an accelerated charged particle can be described theoretically as the interaction of the charge with the so-called Fulling-Davies-Unruh thermal bath in the coordinate frame co-accelerated with the charge. We present a similar analysis on the gravitational radiation from a classical point mass uniformly accelerated, being pulled by a string satisfying the weak energy condition. In particular, we derive the interaction rate (with fixed transverse momentum) of this system of the point mass and string in the Fulling-Davies-Unruh thermal bath in the co-accelerated frame and show that it equals the graviton emission rate calculated in the standard method in Minkowski spacetime.

We explore the cosmology of the dark-dimension scenario taking into account perturbations in the linear regime. In the context of the dark-dimension scenario, a natural candidate for dark matter in our Universe is the excitations of a tower of massive spin-2 Kaluza-Klein (KK) gravitons. These dark gravitons are produced in the early Universe and decay to lighter KK gravitons during the course of cosmological evolution. The decay causes the average dark matter mass to decrease as the Universe evolves. In addition, the kinetic energy liberated in each decay leads to a kick velocity for the dark matter particles, leading to a suppression of structure formation. Using current cosmic microwave background (Planck), baryon acoustic oscillation, and cosmic shear (KiDS-1000) data, we put a bound on the dark matter kick velocity today $v_{\text{today}}\le 2.2\times {10}^{-4}c$ at 95% CL. This leads to rather specific regions of parameter space for the dark-dimension scenario. The combination of the experimental bounds from cosmology, astrophysics, and table-top experiments leads to the range $l_5\sim 1–10\mathrm{\mu }\mathrm{m}$ for the size of the dark dimension. The dark-dimension scenario is found to be remarkably consistent with current observations and provides signatures that are within reach of near-future experiments.

The detectability of light dark matter in direct detection experiments is limited by the small kinetic energy of the recoiling targets. Thus, scenarios where dark matter is boosted to relativistic velocities provide a useful tactic to constrain sub-GeV dark matter particles. Of the possible dark matter boosting mechanisms, cosmic-ray upscattering is an appealing paradigm as it does not require any additional assumptions beyond dark matter coupling to nucleons or electrons. However, detectable signals are obtained only with relatively large cross sections which, in turn, can only be realized with large couplings, light mediators or composite dark matter. In this work we consider a general set of light mediators that couple dark matter to hadrons. Using data from Borexino, XENON1T, LZ and Super-K, we show that existing constraints on such mediators preclude appreciable cosmic-ray dark matter upscattering. This finding highlights the limited applicability of cosmic-ray upscattering constraints and suggests they only be used in model-dependent studies.

Chameleon dark energy models are a popular alternative to the standard cosmological constant model. These models consist of a new light degree of freedom, called chameleon, with a density dependent mass and a nontrivial coupling to both matter and photons. Owing to these couplings, chameleons can be produced inside the sun. However due to their density dependent mass, the chameleons produced in the solar core are screened and cannot escape whereas those produced outside the solar core, such as in the tachocline region with energies of the order of few a keV, can escape from the sun and travel all the way toward Earth. Hence the Earth is expected to receive a flux of solar chameleons. In this work we propose a light shining through wall (LSW) type of experiment in which the Earth itself acts as a wall. Both photons and chameleons are incident on the light side of the Earth. While all the photons are stopped by the Earth, only a fraction of the chameleons are stopped by the earth due to screening. Those chameleons which are not screened by the earth pass directly through the Earth and exit the night side. Here these chameleons interact with the geomagnetic field and convert into x-ray photons. A space-based x-ray telescope orbiting the Earth can detect these x-ray photons, while passing through the night side, thereby acting as a detector in this LSW type experiment. We show that such a kind of setup can be complementary to other terrestrial experiments looking for chameleons.