In this paper we derive exact analytical formulas for the evolution of the photon sphere and for the angular radius of the shadow in a special Vaidya space-time. The Vaidya metric describes a spherically symmetric object that gains or loses mass, depending on a mass function $m(v)$ that can be freely chosen. Here we consider the case that $m(v)$ is a linearly increasing or decreasing function. The first case can serve as a simple model for an accreting black hole, the second case for a (Hawking) radiating black hole. With a linear mass function the Vaidya metric admits a conformal Killing vector field which, together with the spherical symmetry, gives us enough constants of motion for analytically calculating the lightlike geodesics. Both in the accreting and in the radiating case, we first calculate the lightlike geodesics, the photon sphere, the angular radius of the shadow, and the redshift of light in coordinates in which the metric is manifestly conformally static, then we analyze the photon sphere and the shadow in the original Eddington-Finkelstein-like Vaidya coordinates.

We study an inflationary $E$ model with the Gauss-Bonnet coupling, which can enhance the curvature perturbation at small scales and thus produce a significant abundance of primordial black holes (PBHs) and detectable scalar induced gravitational waves (SIGWs). PBHs from the $E$ model with mass $30M_{\odot }$, ${10}^{-5}{M}_{\odot }$, and ${10}^{-12}{M}_{\odot }$ can explain the LIGO-Virgo events, the ultrashort-timescale microlensing events in the OGLE data, and all dark matter, respectively. SIGWs produced by the $E$ model can account for the recent NANOGrav signal. We also compute the primordial non-Gaussianity and discuss its impact on PBHs and SIGWs. The probability distribution of density contrast is modified to be right-tailed, which we find prompts the formation of PBHs, so that the abundance of PBHs is underestimated with Gaussian approximation. On the contrary, the fractional energy density of SIGWs is hardly affected.

Gravitational transitions at low redshifts ($z_t<0.1$) have been recently proposed as a solution to the Hubble and growth tensions. Such transitions would naturally lead to a transition in the absolute magnitude $M$ of type Ia supernovae (SNIa) at $z_t$ (late $M$ transitions—$LMT$) and possibly in the dark energy equation of state parameter $w$ (late $w-M$ transitions). Here, we compare the quality of fit of this class of models to cosmological data, with the corresponding quality of fit of the cosmological constant model ($\mathrm{\Lambda }\mathrm{CDM}$) and some of the best smooth $H(z)$ deformation models [$w\mathrm{CDM}$ (cold dark matter), Chevallier-Polarski-Linder, phenomenologically emergent dark energy]. We also perform model selection via the Akaike information criterion (AIC) and the Bayes factor. We use the full cosmic microwave background temperature anisotropy spectrum data, the baryon acoustic oscillations data, the Pantheon SNIa data, the SNIa absolute magnitude $M$ as determined by Cepheid calibrators and the value of the Hubble constant $H_0$ as determined by local SNIa calibrated using Cepheids. We find that smooth $H(z)$ deformation models perform worse than transition models for the following reasons: (1) they have a worse fit to low-$z$ geometric probes (baryon acoustic oscillations and SNIa data); (2) they favor values of the SNIa absolute magnitude $M$ that are lower as compared to the value $M_c$ obtained with local Cepheid calibrators at $z<0.01$; (3) They tend to worsen the ${\mathrm{\Omega }}_{\mathrm{m},0}-{\sigma }_{8,0}$ growth tension. We also find that the $w-M$ transition model does not provide a better quality of fit to cosmological data than a pure $M$ transition model ($LMT$), where $w$ is fixed to the $\mathrm{\Lambda }\mathrm{CDM}$ value $w=-1$ at all redshifts. We conclude that the $LMT$ model has significant statistical advantages over smooth late-time $H(z)$ deformation models in addressing the Hubble crisis.

Cosmic-ray particles impinging on the atmosphere induce high-energy particle cascades in air, an extensive air shower (EAS), emitting coherent radio emission. This emission is affected by the presence of strong electric fields during thunderstorm conditions. To reconstruct the atmospheric electric field from the measured radio footprint of the EAS we use an analytic model for the calculation of the radio emission, MGMR3D. In this work we make an extensive comparison between the results of a microscopic model for radio emission, CoREAS, to obtain an improved parametrization for MGMR3D in the presence of atmospheric electric fields, as well as confidence intervals. The approach to extract the electric field structure is applied successfully to an event with a complicated radio footprint measured by LOFAR during thunderstorm conditions. This shows that, with the improved parametrization, MGMR3D can be used to extract the structure of the atmospheric electric field.

Feebly interacting particles with masses with $\mathcal{O}(10–100)\mathrm{MeV}$ can be copiously produced by core-collapse supernovae (SNe). In this paper we consider the case of MeV-ish sterile neutrinos and dark photons mixed with ordinary neutrinos and photons, respectively. Furthermore, both sterile neutrinos and dark photons may decay into positrons on their route to Earth. Such positrons would annihilate with electrons in the Galactic medium and contribute to the photon flux in the 511 keV line. Using the spectrometer on INTEGRAL observation of this line improves the bounds on the mixing parameters for these particles by several orders of magnitude below what is already excluded by the SN 1987A energy-loss argument.

We construct a template to model the postmerger phase of a binary black hole coalescence in the presence of a remnant $U(1)$ charge. We include the quasinormal modes typically dominant during a binary black hole coalescence, $(\ell ,m,n)=\{(2,2,0),(2,2,1)\}$ and also present analytical fits for the quasinormal mode frequencies of a Kerr-Newman black hole in terms of its spin and charge, here also including the (3, 3, 0) mode. Aside from astrophysical electric charge, our template can accommodate extensions of the Standard Model, such as a dark photon. Applying the model to LIGO-Virgo detections, we find that we are unable to distinguish between the charged and uncharged hypotheses from a purely postmerger analysis of the current events. However, restricting the mass and spin to values compatible with the analysis of the full signal, we obtain a 90th percentile bound $\overline{q}<0.33$ on the black hole charge-to-mass ratio, for the most favorable case of GW150914. Under similar assumptions, by simulating a typical loud signal observed by the LIGO-Virgo network at its design sensitivity, we assess that this model can provide a robust measurement of the charge-to-mass ratio only for values $\overline{q}\gtrsim 0.5$; here we also assume that the mode amplitudes are similar to the uncharged case in creating our simulated signal. Lower values, down to $\overline{q}\sim 0.3$, could instead be detected when evaluating the consistency of the premerger and postmerger emission.

We discuss a remarkable correspondence between the description of black holes as highly occupied condensates of $N$ weakly interacting gravitons and that of color glass condensates (CGCs) as highly occupied gluon states. In both cases, the dynamics of “wee partons” in Regge asymptotics is controlled by emergent semihard scales that lead to perturbative unitarization and classicalization of $2\to N$ particle amplitudes at weak coupling. In particular, they attain a maximal entropy permitted by unitarity, bounded by the inverse coupling $\alpha$ of the respective constituents. Strikingly, this entropy is equal to the area measured in units of the Goldstone constant corresponding to the spontaneous breaking of Poincaré symmetry by the corresponding graviton or gluon condensate. In gravity, the Goldstone constant is the Planck scale, and gives rise to the Bekenstein-Hawking entropy. Likewise, in the CGC, the corresponding Goldstone scale is determined by the onset of gluon screening. We point to further similarities in black hole formation, thermalization and decay, to that of the glasma matter formed from colliding CGCs in ultrarelativistic nuclear collisions, which decays into a quark-gluon plasma.

We provide two independent systematic methods of performing $D$-dimensional physical-state sums in gauge theory and gravity in such a way so that spurious light-cone singularities are not introduced. A natural application is to generalized unitarity in the context of dimensional regularization or theories in higher spacetime dimensions. Other applications include squaring matrix elements to obtain cross sections, and decompositions in terms of gauge-invariant tensors.

Oscillating neutrino beams exhibit quantum coherence over distances of thousands of kilometers. Their unambiguously quantum nature suggests an appealing test system for direct quantum simulation. Such techniques may enable presently analytically intractable calculations involving multineutrino entanglements, such as collective neutrino oscillations in supernovas, but only once oscillation phenomenology is properly reexpressed in the language of quantum circuits. Here we resolve outstanding conceptual issues regarding encoding of arbitrarily mixed neutrino flavor states in the Hilbert space of an n-qubit quantum computer. We introduce algorithms to encode mixing and oscillation of any number of flavor-mixed neutrinos, both with and without $CP$-violation, with an efficient number of prescriptive input parameters in terms of subrotations of the Pontecorvo-Maki-Nakagawa-Sakata matrix in standard form. Examples encoded for an IBM-Q quantum computer are shown to converge to analytic predictions both with and without $CP$-violation.

A new theoretical framework to describe the experimental advances in electro-optic detection of broadband quantum states, specifically the quantum vacuum, is devised. Electro-optic sampling is a technique in ultrafast photonics which, when transferred into the quantum domain, can be utilized to resolve properties of a sampled quantum state via its interaction with a strong coherent probe pulse at ultrafast timescales. By making use of fundamental concepts from quantum field theory on spacetime metrics, the nonlinear interaction behind the electro-optic effect is shown to be equivalent to a stationary Unruh-DeWitt detector coupled to a conjugate field during a very short time interval. When the coupling lasts for a time interval comparable to the oscillation periods of the detected field mode (i.e., the subcycle regime), virtual particles inhabiting the field vacuum are transferred to the detector in the form of real excitation. We demonstrate that this behavior can be rigorously translated to the scenario of electro-optic sampling of the quantum vacuum, in which the (spectrally filtered) probe works as an Unruh-DeWitt detector, with its interaction-generated photons arising from virtual particles inhabiting the electromagnetic vacuum. Our analysis accurately encapsulates the quantum nature of the vacuum, and we propose the specific working regime in which we can experimentally verify the existence of virtual photons with quantum correlations in the electromagnetic ground state.

We present a parametrization of the chiral even generalized parton distributions, $H$, $E$, $\tilde{H}$, $\tilde{E}$, for the quark, antiquark, and gluon, in the perturbative QCD (pQCD)-parton framework. Parametric analytic forms are given as a function of two equivalent sets of variables $x$, $\xi$, $t$ (symmetric frame) and $X$, $\zeta$, $t$ (asymmetric frame), at an initial scale, $Q_o^2$. In the $X>\zeta$ region, a convenient and flexible form is obtained as the product of a Regge term $\propto X^{-\alpha +{\alpha }^{\prime }t}$, describing the low $X$ behavior, times a spectator model-based functional form depending on various mass parameters; the behavior at $X<\zeta$ is determined using the generalized parton distributions symmetry and polynomiality properties. The parameters are constrained using data on the flavor separated nucleon electromagnetic elastic form factors, the axial and pseudoscalar nucleon form factors, and the parton distribution functions from both the deep inelastic unpolarized and polarized nucleon structure functions. For the gluon distributions we use, in particular, constraints provided by recent lattice QCD moments calculations. The parametrization’s kinematical range of validity is $0.0001\le X\le 0.85$, $0.01\le \zeta \le 0.85$, $0\le -t\le 1{\mathrm{GeV}}^2$, $2\le Q^2\le 100{\mathrm{GeV}}^2$. With the simultaneous description of the quark, antiquark, and gluon sectors, this parametrization represents a first tool enabling a global QCD analysis of deeply virtual exclusive experiments.

The use of extra space-time dimensions provides a promising approach to the flavor problem. The chosen compactification of a 6-dimensional orbifold implies a remnant family symmetry $A_4$. This makes interesting predictions for quark and lepton masses, for neutrino oscillations and neutrinoless double beta decay, providing also a very good global description of all flavor observables. Due to an auxiliary ${\mathbb{Z}}_4$ symmetry, we implement a scotogenic Majorana neutrino mass generation mechanism with a viable WIMP dark matter candidate.

We consider a class of $U(1{)}^{\prime }$-extended minimal supersymmetric extension of the Standard Model (MSSM) in which the $U(1{)}^{\prime }$ symmetry is broken by vacuum expectation values of four MSSM singlet fields. While one MSSM singlet field interacts with the MSSM Higgs fields, three of them interact only with each other in forming a secluded sector. Assigning universal $U(1{)}^{\prime }$ charges for three families, the anomaly cancellation condition requires exotic fields which are assumed to be heavy and decoupled. We discuss a variety of $U(1{)}^{\prime }$ charge assignments and anomaly cancellation, $Z^{\prime }/Z$ hierarchy, neutralinos, charginos and the Higgs sector. We find that the typical spectra involve two $CP$-odd Higgs bosons lighter than about 200 GeV and 600 GeV respectively, which are mostly formed by the MSSM singlet fields. If the relic density of dark matter is saturated only by a neutralino, compatible solutions predict LSP neutralinos formed by the MSSM singlet fields in the mass scales below about 600 GeV, while it is possible to realize MSSM neutralino LSP above these mass scales. One can classify the implications in three scenarios. Scenario I involves NLSP charginos, while Scenario II involves charginos which do not participate coannihilation processes with the LSP neutralino. These two scenarios predict MSSM singlet LSP neutralinos, while Scenario I leads to larger scattering cross sections of dark matter. Scenario III has the solutions in which the MSSM neutralinos are considerably involved in LSP decomposition which yields very large scattering cross section excluded by the direct detection experiments.

We investigate the modification of the Higgs signals from vector boson fusion at the LHC arising from higher-dimensional effective operators involving quarks, electroweak gauge bosons, and the 125 GeV scalar discovered in 2012. Taking a few of the admissible dimension-6 operators as illustration, we work within the framework of the Standard Model effective field theory (SMEFT) and identify kinematic variables that can reflect the presence of such effective operators. The useful variables turn out to be the geometric mean of the transverse momenta of the two forward jets produced in vector boson fusion and the rapidity difference between the two forward jets. We identify the shift in event population caused by the effective operators in the same, spanned by the above kinematic variables. Minimum values of the Wilson coefficients of the chosen dimension-6 operators are identified, for which they can be probed at the $3\sigma$ level in the high-luminosity run of the LHC at 14 TeV. Projected exclusion limits on some of the couplings, obtained from our analysis, can significantly improve the limits on such couplings derived from electroweak precision data.

Hints of lepton flavor universality violation observed in various flavor ratios such as $R_D$, $R_{D^{*}}$, $R_{J/\psi }$, $P_{\tau }^{D^{*}}$, and $F_L^{D^{*}}$ in $B\to D^{(*)}\ell \nu$ and $B_c\to J/\psi \ell \nu$ charge current decays have opened new avenues to search for indirect evidences of beyond the standard model physics. Motivated by these anomalies, we perform a detailed angular analysis of $B_s\to D_s^{*}(\to D_s\gamma ,D_s\pi )\ell \nu$ decays that proceed via similar $b\to c\ell \nu$ quark level transition. We use the most general effective Hamiltonian for $b\to cl\nu$ process and give predictions of several $q^2$ and $\cos \theta$ dependent observables for the $B_s\to D_s^{*}(\to D_s\gamma ,D_s\pi )\ell \nu$ decays in the standard model and in the presence of various real and complex new physics couplings. The results pertaining to this decay are competent to address the anomalies in the charge current sector.

Triggered by experimental prospects to measure electromagnetic dipole moments of baryons containing a bottom quark, we calculate the $CP$-odd electric dipole moments (EDMs) of spin-$1/2$ single-bottom baryons. We consider $CP$-violating dimension-6 operators in the Standard Model effective field theory that involve bottom quarks and apply heavy-baryon chiral perturbation theory to compute the EDMs of several baryons. We discuss the expected size of the EDMs for beyond-the-Standard-Model physics appearing at the TeV scale.

Axions and axionlike particles (ALPs) are some of the most popular candidates for dark matter, with several viable production scenarios that make different predictions. In the scenario in which the axion is born after inflation, its field develops significant inhomogeneity and evolves in a highly nonlinear fashion. Understanding the eventual abundance and distribution of axionic dark matter in this scenario therefore requires dedicated numerical simulations. So far the community has focused its efforts on simulations of the QCD axion, a model that predicts a specific temperature dependence for the axion mass. Here, we go beyond the QCD axion, and perform a suite of simulations on lattice sizes of ${3072}^3$, over a range of possible temperature dependencies labeled by a power-law index $n\in [0,6]$. We study the complex dynamics of the axion field, including the scaling of cosmic strings and domain walls, the spectrum of nonrelativistic axions, the lifetime and internal structure of axitons, and the seeds of miniclusters. In particular, we quantify how much the string-wall network contributes to the dark matter abundance as a function of how quickly the axion mass grows. We find that a temperature-independent model produces 25% more dark matter than the standard misalignment calculation. In contrast to this generic ALP, QCD axion models are almost six times less efficient at producing dark matter. Given the flourishing experimental campaign to search for ALPs, these results have potentially wide implications for direct and indirect searches.

We leverage the $CP$ violation in charged $B$ meson decays to generate the observed baryon asymmetry and dark matter at $\mathcal{O}(10\mathrm{MeV})$ temperatures. We realize this in two scenarios: $B_c^{+}$ mesogenesis and $B^{+}$ mesogenesis. In the first, $CP$-violating $B_c^{\pm }$ decays to $B^{\pm }$ mesons are followed by decays to dark and Standard Model baryons. In the second, $CP$-violating $B^{\pm }$ decays to lighter charged mesons are accompanied by the latter’s decays to dark and Standard Model leptons, which then scatter into the baryon asymmetry. $B_c^{+}$ mesogenesis is actively being probed at Belle and LHCb, while $B^{+}$ mesogenesis can be tested at colliders and sterile neutrino searches.

We study decomposition of SU(2) gauge field into monopole and monopoleless components. After fixing the maximal Abelian gauge in SU(2) lattice gauge theory with Wilson action we decompose the non-Abelian gauge field into the Abelian field created by monopoles and the modified non-Abelian field with monopoles removed. We then calculate respective static potentials in the fundamental and adjoint representations and confirm earlier findings that the sum of these potentials approximates the non-Abelian static potential with good precision at all distances considered. Repeating these computations at three lattice spacings we find that in both representations the approximation becomes better with decreasing lattice spacing. Our results thus suggest that this approximation becomes exact in the continuum limit. We further find the same relation (for one lattice spacing) to be valid also in the cases of improved lattice action and in the theory with quarks.

We provide the first next-to-leading-order (NLO) weak-coupling description of the thermalization process of far-from-equilibrium systems in non-Abelian gauge theory. We study isotropic systems starting from either over- or underoccupied initial conditions and follow their time evolution toward thermal equilibrium by numerically solving the QCD effective kinetic theory at NLO accuracy. We find that the NLO corrections remain well under control for a wide range of couplings and that the overall effect of NLO corrections is to reduce the time needed to reach thermal equilibrium in the systems considered.