We set up and perform collision rate simulations between dark matter in the form of asteroid-mass primordial black holes (PBHs) and white dwarf stars. These encounters trigger prompt detonations and could be the key to solving the ignition mystery of type Ia supernovae. Our framework is flexible enough to cover the full range of progenitor white dwarf masses, host galaxy stellar masses, galactocentric radial offsets, and cosmic time. The rate distribution pattern is consistent with exhaustive literature observational determinations for a slightly extended log-normal PBH mass spectrum. Most strikingly, the so far unexplained brightness distribution comes out without fine-tuning. We find no severe contradictions, except that the inferred PBH mass scale is unpredicted from first principles.

We adopt an effective action inspired by asymptotically safe gravity, in which the effective gravitational constant is parametrized as $G(\epsilon )=G_N/[1+\tilde{\omega }(G_N^2\epsilon {)}^{\alpha }]$, where $G_N$ and $\epsilon$ denote Newton’s gravitational constant and the energy density of the matter field, respectively, with two dimensionless model parameters, $\tilde{\omega }$ and $\alpha$. Within this framework, we investigate the complete gravitational collapse of a homogeneous ball of perfect fluid and find that singularity is completely resolved for $\alpha >1$ but not for $1/2\le \alpha \le 1$. The case of $0<\alpha <1/2$ is inconsistent with asymptotic safety. Moreover, we note that although the singularity cannot be fully resolved for $\alpha =1$, it is significantly weakened by quantum gravity effects. Furthermore, we successfully construct a static exterior metric which, together with the interior solution, describes the dynamical formation of regular black holes in an asymptotically flat spacetime. The resulting regular black hole, obtained as the final static state, contains a de Sitter core and admits a static metric fully expressible in terms of the Lerch transcendent for general cases and in elementary functions for certain values of $\alpha$, including $\alpha =2$. We also discuss the formation of gravastars and the late-time evaporation process of the regular black holes.

There has been an extended debate regarding the existence of a spin-orbital decomposition of the angular momentum of photons and other massless particles. It was recently shown that there are both geometric and topological obstructions preventing any such decomposition. Here we show that any geometric connection on a particle’s state space induces a splitting of the angular momentum into two operators. These operators are well-defined angular momentum operators if and only if the connection has zero curvature. Massive particles have two canonical curved connections corresponding to boosts and rotations, respectively. These can be uniquely combined to produce a flat connection, and this gives a novel derivation of the Newton-Wigner position operator and the corresponding spin and orbital angular momenta for relativistic massive particles. When the mass is taken to zero, transverse boosts and rotations degenerate, leaving only a single connection for massless particles. This connection produces a commonly proposed splitting of the massless angular momentum into two operators. However, the connection is not flat, explaining why these operators do not satisfy the angular momentum commutation relations and are thus not true spin and orbital angular momentum operators.

The Schwinger current, arising from vacuum breakdown in the presence of a strong constant electric pulse background, is well known and has been calculated in numerous studies. It originates from the amplification of zero-point fluctuations. However, we find that higher-loop corrections involve hidden redistributions of the level populations of charged particles and photons. These redistributions lead to corrections to the current, which become significant for sufficiently long pulses and ultimately modify Schwinger’s expression for the current.

In this work, we investigate static and spherically symmetric black hole solutions in $f(R,T)$ gravity, where $R$ is the curvature scalar and $T$ is the trace of the energy-momentum tensor, coupled to nonlinear electrodynamics (NLED). To construct our solutions, we adopt a linear functional form, $f(R,T)=R+\beta T$. In the limit $\beta =0$, the theory reduces to general relativity, recovering $f(R,T)\approx R$. We propose a power-law Lagrangian of the form $\mathcal{L}=f_0+F+\alpha F^p$, where $\alpha =f_0=0$ corresponds to the linear electrodynamics case. Using this setup, we derive the metric functions and determine an effective cosmological constant. Our analysis focuses on specific cases with $p=2$, $p=4$, and $p=6$, where we formulate analytic expressions for the matter fields supporting these solutions in terms of the Lagrangian as a function of $F$. Additionally, we verify the regularity of the solutions and study the structure of the event horizons. Furthermore, we examine a more specific scenario by determining the free forms of the first and second derivatives ${\mathcal{L}}_F(r)$ and ${\mathcal{L}}_{FF}(r)$ of the Lagrangian of the nonlinear electromagnetic field. From these relations, we derive the general form of ${\mathcal{L}}_{\mathrm{NLED}}(r)$ using consistency relations. This Lagrangian exhibits an intrinsic nonlinearity due to the influence of two constants, $\alpha$ and $\beta$. Specifically, $\alpha$ originates from the power-law term in the proposed Lagrangian, while $\beta$ arises from the assumed linear function $f(R,T)$. The interplay of these constants ensures that the nonlinearity of the Lagrangian is governed by both $\alpha$ and $\beta$, rather than $\alpha$ alone. By imposing specific constraints, namely, setting $\alpha =0$ and $\beta =0$, the model reduces to the linear electrodynamics case, while still remaining consistent with the $f(R,T)$ gravity framework. This demonstrates the model’s flexibility in describing both linear and nonlinear regimes.

We study a point scalar charge in circular orbit around a topological star, a regular, horizonless soliton emerging from dimensional compactification of Einstein-Maxwell theory in five dimensions, which could describe qualitative properties of microstate geometries for astrophysical black holes. This is the first step toward studying extreme mass-ratio inspirals around these objects. We show that when the particle probes the spacetime close to the object, the scalar-wave flux deviates significantly from the corresponding black hole case. Furthermore, as the topological star approaches the black-hole limit, the inspiral can resonantly excite its long-lived modes, resulting in sharp features in the emitted flux. Although such resonances are too narrow to produce detectable dephasing, we estimate that a year-long inspiral down to the innermost stable circular orbit could accumulate a significant dephasing for most configurations relative to the black hole case. While a full parameter-estimation analysis is needed, the generically large deviations are likely to be within the sensitivity reach of future space-based gravitational-wave detectors.

Gravitational wave observations are a powerful tool to constrain fundamental physics. This work considers dark matter that carries charge under a dark Abelian massive vector field. If such dark matter is bound inside coalescing neutron stars, the presence of the new force will modify the total energy of the binary, and the emission of dark radiation modes will impact the rate of inspiral. At leading order, the dark matter corrections introduce a Yukawa term to the potential energy and a dipole radiation mode. We calculate modifications to the binary inspiral waveform to first post-Newtonian order, incorporate these corrections into a state-of-the-art waveform model for neutron star binaries, and use this model in a Bayesian parameter estimation analysis on real data collected by current, second-generation ground-based detectors. Through this study, we place the first robust constraints on the Yukawa interaction strength and dipole emission parameter. We find that the strongest constraints are obtained from analysis of the GW170817 event, for which the Yukawa interaction strength is constrained to be less than $\mathcal{O}({10}^{-2})$ and the dipole emission parameter is less than $\mathcal{O}({10}^{-4})$ at 90% credibility.

Black holes offer a unique laboratory for fundamental physics and are crucial for understanding theories beyond Einstein’s theory of general relativity. In this paper, we focus on 4D effective field theories and string-theory inspired models that include scalar fields. We focus on one such model, axi-dilaton gravity, a quadratic gravity theory with two kinetically coupled scalar fields, an axion and a dilaton. To study the evolution and structure of these fields around black holes, we introduce canuda–axidil, the first open-source, parametrized numerical relativity code for quadratic and biscalar gravity. Using this code, we perform single black hole simulations to show the dynamical formation of axion and dilaton hairs and quantify the effect of higher-order terms in coupling and spin. Through these simulations, we measure the impact of black hole spin and curvature coupling strength on the profiles of the axion and dilaton and show that including kinetic coupling between the fields increases the observed deviations from general relativity. Furthermore, we simulate the axion and dilaton fields around a binary black hole coalescence demonstrating the growth of axion hair during the inspiral and the production of radiative modes for both fields.

We consider weakly nonlinear gravitational perturbations of a near-extremal Kerr black hole governed by the second-order vacuum Einstein equation. Using the GHZ [for , Classical Quantum Gravity 7, 075001 (2020)], these are parametrized by a Hertz potential. We make an ansatz for the Hertz potential as a series of zero-damped quasinormal modes (QNMs) with time-dependent amplitudes, and derive a nonlinear dynamical system for them. We find that our dynamical system has a time-independent solution within the near-horizon scaling limit. This equilibrium solution is supported on axisymmetric modes, with amplitudes scaling as $c_{\ell }\sim C^{\mathrm{low}}{2}^{-\frac{\ell }{2}}{\ell }^{-\frac{7}{2}}$ for large polar angular momentum mode number $\ell$, where $C^{\mathrm{low}}$ is a cumulative amplitude of the low $\ell$ modes. We interpret our result as evidence that the dynamical evolution will approach, for a parametrically long time as extremality is approached, a distribution of mode amplitudes exponentially suppressed in $\ell$, hence as the end point of an inverse cascade. It is reminiscent of weatherlike phenomena in certain models of atmospheric dynamics of rotating bodies. During the timescale considered, the decay of the QNMs themselves plays no role given their parametrically long half-life. Hence, our result is due entirely to weakly nonlinear effects.

The dipole anisotropy induced by our peculiar motion in the sky distribution of cosmologically distant sources is an important consistency test of the standard Friedmann-Lemaître-Robertson-Walker cosmology. In this work, we formalize how to compute the kinematic matter dipole in redshift bins. Apart from the usual terms arising from angular aberration and flux boosting, there is a contribution from the boosting of the redshifts that becomes important when considering a sample selected on observed redshift, leading to nonvanishing correction terms. We discuss examples and provide expressions to incorporate arbitrary redshift selection functions. We also discuss the effect of redshift measurement uncertainties in this context, in particular in upcoming surveys for which we provide estimates of the correction terms. Depending on the shape of a sample’s redshift distribution and on the applied redshift cuts, the correction terms can become substantial, even to the degree that the direction of the dipole is reversed. Lastly, we discuss how cuts on variables correlated with observed redshift, such as color, can induce additional correction terms.

The observed cosmological constant may originate as the minimum value $U_{\min }$ of a scalar field potential, where the scalar field is frozen due to a large mass $m$. If this vacuum is metastable, it may decay to a true vacuum either at present or in the future. Assuming its decay rate $\mathrm{\Gamma }$ is comparable to the Hubble expansion rate $H_0$, we estimate the scale of true vacuum bubbles and analyze their evolution. We find that their initial formation scale is submillimeter, and their tension causes rapid collapse if $m\gtrsim 1.7\times {10}^{-3}\mathrm{eV}$. For smaller masses, the bubbles expand at the speed of light. We extend our analysis to scalar-tensor theories with nonminimal coupling, finding that the nucleation scale of gravitational constant bubbles remains consistent with the submillimeter regime of general relativity. The critical mass scale remains around ${10}^{-3}\mathrm{eV}$, similar to the minimally coupled case. A theoretical estimate at redshift $z_{\mathrm{obs}}\sim 0.01$ suggests an observable bubble radius of $\sim 50\mathrm{Mpc}$, implying a gravitational transition triggered $\sim 300\mathrm{Myr}$ ago, with a present-day size approaching 100 Mpc. Additionally, we explore mass ranges ($m<{10}^{-3}\mathrm{eV}$) and coupling parameter $\xi$ ranges (${10}^{-8}{\mathrm{eV}}^{2-n}$ to ${10}^{-1}{\mathrm{eV}}^{2-n}$) that lead to a variation in the gravitational constant $\mathrm{\Delta }G/G_N$ within the 1%–7% range. This analysis is conducted in the framework of nonminimal coupling theories, where the coupling function takes the form $F(\varphi )=1/\kappa -\xi {\varphi }^n$, with $\kappa =8\pi G_N$ and $2\le n\le 9$. Finally, we review various local physics or/and transition based proposed solutions to the Hubble tension, including ultralate-time transitional models ($z\sim 0.01$), screened fifth-force mechanisms, and the ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$ model, which features a transition at $z\sim 2$. We discuss observational hints supporting these scenarios and the theoretical challenges they face.

The dark matter (DM) conundrum is one of the most intriguing due to its resistance in direct detection experiments. In recent years, attempts to identify nongravitational signatures as the result of DM traversing or accumulating within stars have attracted a lot of attention. These calculations are usually evaluated at the order-of-magnitude level for stellar populations where the DM density is highest, such as galactic centers. However, if the signature implies the destruction of the host star, their population could have been diminished over a Hubble time in the most DM-dense regions, unless replenished by star formation. This circumstance exemplifies the need for galactic star formation history profiles when deriving DM-induced transient rates, in particular for predicting the host-offset distribution. Here, we combine theoretical and empirical scaling relations of galaxy structure, star formation, and stellar initial mass function to construct a simple and efficient framework that permits us to estimate the target population formation rate and mass function within galactocentric radial zones across galaxy stellar masses and cosmic time. In a companion paper, we apply the framework to the hypothesis that DM in the form of primordial black holes accounts for the ignition of normal type Ia supernovae when colliding with white dwarf stars.

In this paper, we examine the neutrino signals from 24 initially nonrotating, three-dimensional core-collapse supernova (CCSN) simulations carried to late times. We find that not only does the neutrino luminosity signal encode information about each stage of the CCSN process, but that the monotonic dependence of the luminosity peak height with compactness enables one to infer the progenitor core structure from the neutrino signal. We highlight a systematic relationship between the luminosity peak height with its timing. Additionally, we emphasize that the total energy radiated in neutrinos is monotonic with progenitor compactness, and that the mean neutrino energy contains a unique spiral Standing Accretion Shock Instability (SASI) signature for nonexploding, black hole (BH)-forming models. We also find that neutrino emissions are not isotropic and that the anisotropy increases roughly with progenitor compactness. To assess the detectability of these neutrino signal features, we provide examples of the event rates for our models for the JUNO, DUNE, SK, and IceCube detectors using the snewpy software [A. L. Baxter et al. (Snews Collaboration), snewpy: A data pipeline from supernova simulations to neutrino signals, Astrophys. J. 925, 107 (2022)], and find that many of the trends in the luminosity signal can be detectable across several detectors and oscillation models. Finally, we discuss correlations between the radiated neutrino energy and the evolution of the gravitational-wave f-mode.

Many quantum gravity theories predict deviations from Lorentz invariance, a foundational principle of modern physics, at energy scales exceeding the Planck scale. The presence of Lorentz invariance violation (LIV) would modify the dispersion relations of particles in vacuum and render certain decay channels kinematically permissible. In this study, we derive stringent constraints on the energy scale of LIV in the neutrino sector by investigating the impact of neutrino decay channels on the neutrino spectrum in the presence of LIV. Utilizing the spectra derived from the joint fit of KM3NeT, IceCube, and Auger data as a benchmark, we demonstrate that to be compatible with the highest-energy neutrino event ever detected, known as event KM3-230213A, the second-order LIV energy scale must satisfy ${\mathrm{\Lambda }}_2>5.0\times {10}^{19}\mathrm{GeV}$ at 90% confidence level. Furthermore, our analyses indicate that the current data do not impose a stringent constraint on the energy scale associated with the first-order LIV.

Properties of interstellar environment near the solar system have been probed by missions like IBEX, Voyager over the last two decades. Although it has been well recognized that properties of cosmic rays up to the PeV energy can be affected by the local interstellar environment, detailed modeling has not been done. We show that a three component model for the cosmic ray proton and helium spectra from GV to several PV can naturally explain the energy dependence of the dipole anisotropy of cosmic ray fluxes by considering effects of the local interstellar environment on cosmic ray transport, addressing the so-called cosmic ray anisotropy problem. In particular, it is shown that the dipole amplitude and position angle below $\sim 100\mathrm{TeV}$ are very sensitive to the velocity of the heliosphere in the local interstellar cloud and the motion of the local interstellar cloud in the local standard of rest. Better measurement of cosmic ray flux anisotropy by experiments like LHAASO and properties of the local interstellar environment by future missions like IMAP will be able to test this model.

Parametric representations of the high-density nuclear equation of state are used in constructing models for interpreting the astrophysical observations of neutron stars. This study explores how accurately equations of state with strong first-order phase transitions can be represented using spectral or piecewise analytic methods that assume no a priori knowledge of the location or the strength of the phase transition. The model equations of state used in this study have phase transitions strong enough to induce a gravitational instability that terminates the sequence of stable neutron stars. These equations of state also admit a second sequence of stable stars with core matter that has undergone this strong first-order phase transition (possibly driven by quark deconfinement). These results indicate that spectral representations generally achieve somewhat higher accuracy than piecewise analytic representations having the same number of parameters. Both types of representation show power-law convergence at approximately the same rate.

We perform analysis of the small $x$ nonlinear evolution equation formulated in momentum space supplemented by higher order terms. The equation is defined in the wide range of transverse momentum and longitudinal momentum fractions extending previous studies performed in Kutak and Kwiecinski [Screening effects in the ultrahigh-energy neutrino interactions, Eur. Phys. J. C 29, 521 (2003).] and in Kutak and Stasto [Unintegrated gluon distribution from modified BK equation, Eur. Phys. J. C 41, 343 (2005).]. The linear part of the equation is motivated by the renormalization group improved small $x$ approach, which accounts for resummation of higher orders, and includes collinear splitting functions and kinematical constraints. The solution to the equation is then used to perform the fit to deep inelastic scattering reduced cross section data.

We explore the discovery potential of ultraheavy $(7–8.5\mathrm{TeV})$ diquark scalars $(S_{uu})$ produced in the collision of two up quarks at the LHC. Assuming that the diquark scalar decays into two vectorlike quarks of mass around 2 TeV, each of them decaying into a $W^{+}$ boson and a $b$ quark, we focus on the fully hadronic final state. We present a signal-from-background separation study based on a discriminator built with machine learning techniques. For this six-jet final state and a luminosity of $3000{\mathrm{fb}}^{-1}$, we estimate that a diquark scalar of mass near 8 TeV may be discovered or ruled out even when its coupling to up quarks is as low as 0.2.

The long-standing flavor anomalies in $b\to s{\ell }^{+}{\ell }^{-}$ and $b\to c\ell \nu$ persist. In this work, we explore a specific flavor-gauged two-Higgs-doublet model (FG2HDM) extended by a scalar singlet, with an imposed $U(1)$ flavor symmetry. Compared to the standard model (SM), four additional scalars and one neutral gauge boson $Z^{\prime }$ are added to the particle spectrum. The special Yukawa coupling matrices, due to the $U(1)$ symmetry, lead to flavor-changing neutral Higgs interactions uniquely occurring in the down-type quark sector, while the new gauge boson $Z^{\prime }$ induces flavor-changing neutral current interactions in the down-type quark sector as well. The two distinct types of anomalies can be accommodated simultaneously in such a model. Incorporating scalar and vector contributions to $b\to s{\ell }^{+}{\ell }^{-}$, $B_s\to {\mu }^{+}{\mu }^{-}$, and $B_s^0-{\overline{B}}_s^0$ mixing, charged Higgs contributions to $b\to c\ell \nu$, along with electroweak precision observables and Higgs fermionic decays, we investigate the parameter space in FG2HDM and find substantial room in the solution space. Specifically, in the SM-like model setup, the data suggest that $m_{Z^{\prime }}<450\mathrm{GeV}$, $\tan \beta <28$, and $g^{\prime }/m_{Z^{\prime }}>3.5\times {10}^{-4}{\mathrm{GeV}}^{-1}$, while there are fewer constraints on heavy scalars, which can be further tested by a combination of other observables.