We propose a regularization procedure in the sourced Weyl double copy, a spinorial version of the classical double copy, such that it matches much more general results in the Kerr-Schild version. In the regularized Weyl double copy, the anti–de Sitter (AdS) and the Lifshitz black holes, which form the basis of the study of strongly coupled gauge theories at finite temperature through the $\mathrm{AdS}/\mathrm{CFT}$ correspondence and its nonrelativistic generalization, become treatable. We believe that this might pave the way for finding a relation between the classical double copy and holography.

Deviations from general relativity can alter the quasinormal mode (QNM) ringdown of perturbed black holes. It is known that a shift-symmetric (hence massless) scalar can only introduce black hole hair if it couples to the Gauss-Bonnet invariant, in which case the scalar charge is fixed with respect to the black hole mass and controlled by the strength of that coupling. The charge per unit mass decreases with the mass and can, therefore, be used as a perturbative parameter for black holes that are sufficiently large with respect to the scale suppressing the deviation from general relativity or the Standard model. We construct an effective field theory scheme for QNMs using this perturbative parameter to capture deviations from Kerr for both the background and the perturbations. We demonstrate that up to second order in the charge per unit mass, QNMs can be calculated by solving standard linearized perturbation equations for the Kerr metric with sources depending on solutions of the same equations up to first order. It follows that corrections to the QNM frequencies are heavily suppressed for sufficiently massive black holes, meaning that LISA is very unlikely to detect any evidence of scalar hair in ringdown signals.

The recent detection of a stochastic signal in the NANOGrav 15-year dataset has aroused great interest in uncovering its origin. However, the evidence for the Hellings-Downs correlations, a key signature of the gravitational-wave background (GWB) predicted by general relativity, remains inconclusive. In this paper, we search for an isotropic nontensorial GWB, allowed by general metric theories of gravity, in the NANOGrav 15-year dataset. Our analysis reveals a Bayes factor of approximately 2.5, comparing the quadrupolar (tensor transverse, TT) correlations to the scalar transverse (ST) correlations, suggesting that the ST correlations provide a comparable explanation for the observed stochastic signal in the NANOGrav data. We obtain the median and the 90% equal-tail amplitudes as ${\mathcal{A}}_{\mathrm{ST}}={7.8}_{-3.5}^{+5.1}\times {10}^{-15}$ at the frequency of $1/\mathrm{year}$. Furthermore, we find that the vector longitudinal (VL) and scalar longitudinal (SL) correlations are weakly and strongly disfavored by data, respectively, yielding upper limits on the amplitudes: ${\mathcal{A}}_{\mathrm{VL}}^{95\%}\lesssim 1.7\times {10}^{-15}$ and ${\mathcal{A}}_{\mathrm{SL}}^{95\%}\lesssim 7.4\times {10}^{-17}$. Lastly, we fit the NANOGrav data with the general transverse (GT) correlations parametrized by a free parameter $\alpha$. Our analysis yields $\alpha ={1.74}_{-1.41}^{+1.18}$, thus excluding both the TT ($\alpha =3$) and ST ($\alpha =0$) models at the 90% confidence level.

Certain versions of mimetic gravity have recently been claimed to present potential covariant theories of canonically modified spherically symmetric gravity, motivated by ingredients from loop quantum gravity. If such an equivalence were to hold, it would demonstrate general covariance of a large class of models considered in loop quantum gravity. However, the relationship with mimetic gravity as presented so far is incomplete because it has been proposed only in preferred space-time slicings of uniform scalar fields. Here, several independent arguments are used to show that neither an equivalence nor a covariance claim are correct for models of loop quantum gravity. The framework of emergent modified gravity is found to present a broad setting in which such questions can be analyzed efficiently. As an additional result, the discussion sheds light on the coexistence of different and mutually inequivalent approaches to an implementation of the gravitational dynamics within loop quantum gravity.

We present the analytical solutions for the trajectories of particles that spiral and plunge inward of the event horizon along the timelike geodesics following general nonequatorial paths within Kerr-Newman spacetimes. Our studies encompass both bound and unbound motions. The solutions can be written in terms of the elliptical integrals and the Jacobian elliptic functions of manifestly real functions of the Mino time. They can respectively reduce to the Kerr, Reissner-Nordström, and Schwarzschild black holes in certain limits of the spin and charge of the black holes, and can be compared with the known ones restricted in equatorial motion. These explicit solutions may have some implications for the gravitational wave emission from extreme mass-ratio inspirals.

We test ideas of the recently proposed first-order thermodynamics of scalar-tensor gravity using an exact geometry sourced by a conformally coupled scalar field. We report a nonmonotonic behavior of the effective “temperature of gravity” not observed before and due to a new term in the equation describing the relaxation of gravity toward its state of equilibrium, i.e., Einstein gravity, showing a richer range of thermal behaviors of modified gravity than previously thought.

Inflation is a highly favored theory for the early Universe. It is compatible with current observations of the cosmic microwave background and large scale structure and is a driver in the quest to detect primordial gravitational waves. It is also, given the current quality of the data, highly underdetermined with a large number of candidate implementations. We use a new method in symbolic regression to generate all possible simple scalar field potentials for one of two possible basis sets of operators. Treating these as single-field, slow-roll inflationary models we then score them with an information-theoretic metric (“minimum description length”) that quantifies their efficiency in compressing the information in current data. We explore two possible priors on the parameter space of potentials, one related to the functions’ structural complexity and one that uses a Katz back-off language model to prefer functions that may be theoretically motivated. This enables us to identify the inflaton potentials that optimally balance simplicity with accuracy at explaining current data, which may subsequently find theoretical motivation. Our exploratory study opens the door to extraction of fundamental physics directly from data, and may be augmented with more refined theoretical priors in the quest for a complete understanding of the early Universe.

Elastic scattering of dark matter (DM) particles with baryons induce cosmological signals that may be detectable with modern or future telescopes. For DM-baryon scattering cross sections scaling with negative powers of relative velocity, ${\sigma }_{\chi b}(v)\propto v^{-2},v^{-4}$, such interactions introduce a momentum-exchange rate that is nonlinear in DM-baryon bulk relative velocities, thus not amenable for inclusion as-is into standard linear cosmological Boltzmann codes. Linear Ansätze have been adopted in past works, but their accuracy is unknown as they do not arise from first-principles derivations. In this work, for the first time, we construct a rigorous framework for computing linear-cosmology observables as a perturbative expansion in ${\sigma }_{\chi b}$. We argue that this approach is accurate for cosmic microwave background (CMB) angular power spectra when most or all of the DM is scattering with baryons with cross section ${\sigma }_{\chi b}(v)\propto v^{-2},v^{-4}$. We derive exact formal expressions for CMB power spectra at linear order in ${\sigma }_{\chi b}$, and show that they only depend on a specific velocity integral of the momentum-exchange rate. Consequently, we can obtain the exact power spectra at linear order in ${\sigma }_{\chi b}$ by substituting the original nonlinear momentum-exchange rate with a uniquely specified linear rate. Serendipitously, we find that the exact substitution we derive from first principles precisely coincides with the most widely used linear Ansatz, thus placing previous CMB-anisotropy upper bounds on more solid footing. In addition to finally providing an exact cosmological solution to the DM-baryon scattering problem in a well-defined region of parameter space, the framework we construct opens the way to computing higher-order correlation functions, beyond power spectra, which are promising, yet unexplored, probes of DM-baryon scattering.

The next Milky Way supernova will be an epochal event in multimessenger astronomy, critical to tests of supernovae, neutrinos, and new physics. Realizing this potential depends on having realistic simulations of core collapse. We investigate the neutrino predictions of modern models (1-, 2-, and 3-D) over the first $\simeq 1\mathrm{s}$, making the first detailed comparisons of these models to each other and to the SN 1987A neutrino data. Even with different methods and inputs, the models generally agree with each other. However, even considering the low neutrino counts, the models generally disagree with data. What can cause this? We show that neither neutrino oscillations nor different progenitor masses appear to be a sufficient solution. We outline urgently needed work.

In the context of the Laser Interferometer Space Antenna (LISA), the laser subsystems exhibit frequency fluctuations that introduce significant levels of noise into the measurements, surpassing the gravitational wave signal by several orders of magnitude. Mitigation is achieved by means of time-shifting individual measurements in a data processing step known as time-delay interferometry (TDI). The suppression performance of TDI relies on accurate knowledge and consideration of the delays experienced by the interfering lasers. While considerable efforts have been dedicated to the accurate determination of inter-spacecraft ranging delays, the sources for delays onboard the spacecraft have been either neglected during TDI processing or assumed to be known. Contrary to these assumptions, analog delays of the phasemeter front end and the laser modulation are not only large but also prone to change with temperature and heterodyne frequency. This motivates our proposal for a novel method enabling a calibration of these delays on-ground and in-space, based on minimal functional additions to the receiver architecture. Specifically, we establish a set of calibration measurements and elucidate how these measurements are utilized in data processing, leading to the mitigation of the delays in the TDI Michelson variables. Following a performance analysis of the calibration measurements, the proposed calibration scheme is assessed through numerical simulations. We find that in the absence of the calibration scheme, the assumed drifts of the analog delays increase residual laser noise at high frequencies of the LISA measurement band. A single, on-ground calibration of the analog delays leads to an improvement by roughly one order of magnitude, while recalibration in space may improve performance by yet another order of magnitude. Towards lower frequencies, ranging error is always found to be the limiting factor for which countermeasures are discussed.

We study the stochastic gravitational wave (GW) background resulting from the strong first-order phase transition (SFOPT) associated with $SU(2{)}_R\times U(1{)}_{B-L}$-breaking in the doublet left-right symmetric model (DLRSM). For different values of the symmetry-breaking scale $v_R=20$, 30, and 50 TeV, we construct the one-loop finite temperature effective potential to explore the parameter space for regions showing SFOPT. We identify the region where the associated GW background is strong enough to be detected at planned GW observatories. A strong GW signature favors a relatively light $CP$-even neutral scalar $H_3$, arising from the $SU(2{)}_R$ doublet. The $SU(2{)}_L$ subgroup of DLRSM is broken by three vacuum expectation values: ${\kappa }_1$, ${\kappa }_2$, and $v_L$. We observe a preference for $\mathcal{O}(1)$ values of the ratio $w=v_L/{\kappa }_1$, but no clear preference for the ratio $r={\kappa }_2/{\kappa }_1$. A large number of points with strong GW signal can be ruled out from precise measurement of the trilinear Higgs coupling and searches for $H_3$ at the future colliders.

We propose a novel method using the $ZZ$-fusion channel and forward muon detection at high energy muon colliders to address the challenge of the Higgs coupling-width degeneracy. Our approach enables inclusive Higgs rate measurement to 0.75% at 10 TeV muon collider, breaking the coupling-width degeneracy. Results indicate the potential to refine Higgs coupling to subpercent levels and estimate its total width within ($-0.41\%$, $+2.1\%$). Key insights include the effectiveness of forward muon tagging in signal-background separation despite broad recoil mass distribution due to muon energy reconstruction and beam energy spread. The study emphasizes the significance of muon rapidity coverage up to $|\eta (\mu )|<6$, enhancing measurement precision. Our findings highlight the unique capabilities of high energy lepton colliders for model-independent Higgs coupling determination and lay the groundwork for future advancements in muon collider technology and Higgs physics research.

An updated analysis of the two-body $D\to PP,VP$, and $VV$ decays within the framework of the topological diagram approach is performed. A global fit to the Cabibbo-favored (CF) modes in the $VP$ sector gives many solutions with similarly small local minima in ${\chi }^2$. The solution degeneracy is lifted once we use them to predict for the singly-Cabibbo-suppressed modes. Topological amplitudes are extracted for the $\eta -{\eta }^{\prime }$ mixing angles $\varphi =40.4°$ and 43.5°. The $K_S^0-K_L^0$ asymmetries in $D\to K_{S,L}^{0}M$ decays denoted by $R(D,M)$ are studied. While the predicted $R(D^0,P)$ for $P={\pi }^0,\eta$ and ${\eta }^{\prime }$ agree with experiment, the calculated $R(D^{+},{\pi }^{+})$, $R(D_s^{+},K^{+})$, $R(D^0,\omega )$, and $R(D^0,\varphi )$ deviate from the data. We conjecture that the relative phase between the topological amplitudes ($C+A$) and ($T+C$) should be slightly smaller than 90° in order to explain the first two discrepancies and that additional singlet contributions due to the SU(3)-singlet nature of $\omega$ and $\varphi$ are needed to account for the last two. For doubly-Cabibbo-suppressed (DCS) $D\to VP$ decays, their topological amplitudes (double primed) cannot be all the same as the corresponding ones in the CF modes. The assumption of $E_{V,P}^{\prime \prime }=E_{V,P}$ for the $W$-exchange amplitude leads to some inconsistencies with the experiment. Through the measured relative phases between CF and DCS channels, the relations of $E_{V,P}^{\prime \prime }$ with $E_{V,P}$ are determined. Long-distance contributions to the $D^0-{\overline{D}}^0$ mixing parameter $y$ are evaluated in the exclusive approach. In particular, we focus on $D\to PP$ and $VP$ decays where $y$ can be reliably estimated. We conclude that $y_{PP}\sim (0.110\pm 0.011)\%$ and the lower bound on $y_{VP}$ is $(0.220\pm 0.071)\%$. It is thus conceivable that at least half of the mixing parameter $y$ can be accounted for by the two-body $PP$ and $VP$ modes. The main uncertainties arise from the yet-to-be-measured DCS channels and their phases relative to the CF ones.

A muonium consists of a positive muon associated with an orbital electron, and the spontaneous conversion to antimuonium serves as a clear indication of new physics beyond the Standard Model in particle physics. One of the most important aspects in muonium-to-antimuonium conversion experiment is to increase the muonium yield in vacuum to challenge the latest limit obtained in 1999. This study focuses on a simulation of the muonium formation and diffusion in the perforated silica aerogel. The independent simulation results can be well-validated by experimental data. By optimizing the target geometry, we find a maximum muonium emission efficiency of 7.92(2)% and a maximum vacuum yield of 1.134(2)% with a typical surface muon beam, indicating a 2.6 times and a 2.1 times enhancement, respectively. Our results will pave the way for muonium experiments.

For the first time, we show high-fidelity generation of Liquid Argon Time Projection Chamber (LArTPC-like) data using a generative neural network. This demonstrates that methods developed for natural images do transfer to LArTPC-produced images, which, in contrast to natural images, are globally sparse but locally dense. We present the score-based diffusion method employed. We evaluate the fidelity of the generated images using several quality metrics, including modified measures used to evaluate natural images, comparisons between high-dimensional distributions, and comparisons relevant to LArTPC experiments.

We show that it is possible to define a timelike future-directed information current within relativistic first-order hydrodynamics. This constitutes the first step toward a covariantly stable and causal formulation of first-order fluctuating hydrodynamics based on thermodynamic principles. We provide several explicit examples of first-order theories with an information current, covering many physical phenomena, ranging from electric conduction to viscosity and elasticity. We use these information currents to compute the corresponding equal-time correlation functions, and we find that the physically relevant (equal-time) correlators do not depend on the choice of the hydrodynamic frame as long as the frame leads to causal and stable dynamics. In the example of chiral hydrodynamics, we find that circularly polarized shear waves have different probabilities of being excited depending on their handedness, generating net helicity in chiral fluids.

The second Mellin moments $⟨x⟩$ of the nucleon’s unpolarized, polarized, and transversity parton distribution functions are computed. Two lattice QCD ensembles at the physical pion mass are used: these were generated using a tree-level Symanzik-improved gauge action and $2+1$ flavor tree-level improved Wilson Clover fermions coupling via 2-level HEX-smearing. The moments are extracted from forward matrix elements of local leading twist operators. We determine renomalization factors in RI-(S)MOM and match to $\overline{\mathrm{MS}}$ at scale 2 GeV. Our findings show that operators that exhibit vanishing kinematics at zero momentum can have significantly reduced excited-state contamination. The resulting polarized moment is used to quantify the longitudinal contribution to the quark spin-orbit correlation. All our results agree within two sigma with previous lattice results.

A search is presented for charged, long-lived supersymmetric particles in final states with one or more disappearing tracks. The search is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector at the CERN LHC between 2016 and 2018, corresponding to an integrated luminosity of $137{\mathrm{fb}}^{-1}$. The search is performed over final states characterized by varying numbers of jets, $b$-tagged jets, electrons, and muons. The length of signal-candidate tracks in the plane perpendicular to the beam axis is used to characterize the lifetimes of wino- and Higgsino-like charginos produced in the context of the minimal supersymmetric standard model. The $\mathrm{d}E/\mathrm{d}x$ energy loss of signal-candidate tracks is used to increase the sensitivity to charginos with a large mass and thus a small Lorentz boost. The observed results are found to be statistically consistent with the background-only hypothesis. Limits on the pair-production cross section of gluinos and squarks are presented in the framework of simplified models of supersymmetric particle production and decay, and for electroweakino production based on models of wino and Higgsino dark matter. The limits presented are the most stringent to date for scenarios with light third-generation squarks and a wino- or Higgsino-like dark matter candidate capable of explaining the observed dark matter relic density.

We study a toy model of continuous infinite expansion of space-time with the flat start. We use as the gravitational background a conformally flat metric with an exponentially growing factor in conformal time. We aim to clarify some properties of quantum fields in such a gravitational background. In particular, we calculate one-loop corrections to the Keldysh propagator to verify the fact of secular growth of the occupation number and anomalous quantum average in the massless scalar field theory with self-interactions. We perform the calculation in arbitrary dimensions with the use of the Schwinger-Keldysh technique. We get a secular growth that is not of a kinetic type. We provide some results for the case of generic interaction $\frac{\lambda }{b!}{\varphi }^b$.

A semiclassical investigation of the electromagnetic radiation emitted by a charged particle in a radially freely falling motion in Schwarzschild spacetime is carried out. We use quantum field theory at tree level to obtain the one-particle-emission amplitudes. We analyze and compare the energy spectrum and total energy released, which are calculated from these amplitudes, for particles with varying initial positions and for particles originating from infinity with varying kinetic energy. We also compare the results with those due to a falling charged “string” extended in the radial direction.