We developed a new general-relativistic quantum-kinetics neutrino transport code, GRQKNT, for numerical studies of quantum kinetics of nonequilibrium neutrinos in six-dimensional phase space. This code is intended for use in both local and global simulations of neutrino transport in a core-collapse supernova and binary neutron star merger. It has been widely recognized that global simulations of collective neutrino oscillations, in particular, fast neutrino-flavor conversions, require unfeasible computational resources due to large disparity of scales between flavor conversion and astrophysical phenomena. We propose a novel approach to tackle the issue. This paper is devoted to describe the philosophy, design, and numerical implementation of GRQKNT with a number of tests ensuring correct implementation of each module. The code is based on a discrete-ordinate Sn method, finite-difference realization of mean-field quantum kinetic equation. The transport equation is solved based on a conservative formalism, and we use a fifth-order weighted essentially nonoscillatory scheme with fourth-order total variation diminishing Runge-Kutta time integration. The transport module is designed to work with arbitrary spacetimes, and currently three different stationary spacetimes (the flat spacetime, Schwarzschild black hole, and Kerr black hole) are implemented. The collision term including neutrino emission, absorption, and momentum-exchanged scatterings are also implemented into our code. The oscillation Hamiltonian consists of vacuum, matter, and self-interactions. Both two- and three neutrino-flavor scenarios can be applied. Fluid-velocity dependencies in transport, collision, and oscillation modules are also treated self-consistently by using the two-energy-grid technique, which has been already established in another code with full Boltzmann neutrino transport.

We determine the kinetic coefficients of ultrasoft pions using chiral perturbation theory at finite temperature close to the chiral limit. This is used to compute the axial charge diffusion and damping coefficients in the hydrodynamic effective theory for these pion waves. We show that to provide a leading order answer for these coefficients one needs to explore the dynamics of hard, soft, and ultrasoft pion modes, which are represented microscopically by the appropriate kinetic and hydrodynamic descriptions.

We study a modification of the Higgs inflation scenario where we introduce an extra scalar $\varphi$, with mass $m$, coupled to the Ricci scalar as $g{\varphi }^{2}R$, and mixed with the Higgs field $h$ via the Lagrangian term $\mu \varphi h^2$. Both fields participate in the inflation process in a unitary theory that predicts values of the cosmological observables in agreement with the results from the Planck/BICEP/Keck collaborations. In addition, by means of a $\mathcal{CP}$-odd effective operator that couples $\varphi$ to the Chern-Simons term of the hypercharge gauge group as $f_{\varphi }^{-1}\varphi Y_{\mu \nu }{\tilde{Y}}^{\mu \nu }$, maximally helical magnetic fields are produced during the last $e$-folds of inflation. We found a window in the coupling $f_{\varphi }$ where these fields survive all constraints until the electroweak phase transition, and source the baryon asymmetry of the Universe through the Standard Model chiral anomaly. From a phenomenological perspective, the model can solve the Standard Model instability problem at the scale ${\mathcal{Q}}_I\simeq {10}^{11}\mathrm{GeV}$, provided that $\mu \lesssim m\lesssim {\mathcal{Q}}_I$, and for $m\lesssim \mathcal{O}(\mathrm{few})\mathrm{TeV}$, the $\varphi -h$ mixing becomes sizable while the theory turns natural. The latter thus predicts modifications of the trilinear and quartic couplings that could be explored at the HE-LHC, as well as at future colliders, and allows for direct $\varphi$ production at the LHC followed by decay into $hh$. Present results from ATLAS and CMS already put (mild) bounds on the mass of the heavy scalar as $m\gtrsim 0.55\mathrm{TeV}$ at 95% CL.

We present simulations of nonequilibrium dynamics of quantum field theories on digital quantum computers. As a representative example, we consider the Schwinger model, a ($1+1$)-dimensional U(1) gauge theory, coupled through a Yukawa-type interaction to a thermal environment described by a scalar field theory. We use the Hamiltonian formulation of the Schwinger model discretized on a spatial lattice. With the thermal scalar fields traced out, the Schwinger model can be treated as an open quantum system and its real-time dynamics are governed by a Lindblad equation in the Markovian limit. The interaction with the environment ultimately drives the system to thermal equilibrium. In the quantum Brownian motion limit, the Lindblad equation is related to a field theoretical Caldeira-Leggett equation. By using the Stinespring dilation theorem with ancillary qubits, we perform studies of both the nonequilibrium dynamics and the preparation of a thermal state in the Schwinger model using IBM’s simulator and quantum devices. The real-time dynamics of field theories as open quantum systems and the thermal state preparation studied here are relevant for a variety of applications in nuclear and particle physics, quantum information and cosmology.

Building on the experience of [A. Hietanen et al., Phys. Rev. D $\mathbf{79}$, 045018 (2009)], we develop a formalism to construct operators for higher derivatives of the pressure in hot QCD with respect to the quark chemical potential $\mu$. We provide formulas for the operators up to the sixth derivative, and obtain continuum-extrapolated results from lattice electrostatic QCD (EQCD) at zero and finite $\mu$ and at six different pairs of temperature $T$ and number of massless quark flavors $n_{\mathrm{f}}$. Our data is benchmarked against full-QCD lattice and perturbative results, allowing us to judge the quality of the perturbative series expansion in EQCD and the dimensional reduction procedure as a whole.

We calculate differential cross sections for $c\overline{c}$- and $b\overline{b}$-dijet production in $pp$ scattering at $\sqrt{s}=13\mathrm{TeV}$ in the $k_T$-factorization and hybrid approaches with different unintegrated parton distribution functions (uPDFs). We present distributions in the transverse momentum and pseudorapidity of the leading jet, the rapidity difference between the jets and the dijet invariant mass. Our results are compared to recent LHCb data on forward production of heavy-flavor dijets, measured recently for the first time individually for both charm and bottom flavors. We find that an agreement between the predictions and the data within the full $k_T$ factorization is strongly related to the modeling of the large-$x$ behavior of the gluon uPDFs, which is usually not well constrained. The problem may be avoided following the hybrid-factorization approach. Then, we obtain a good description of the measured distributions with the parton-branching, Kimber-Martin-Ryskin, Kutak-Sapeta, and Jung setA0 models for the gluon uPDF. We also calculate differential distributions for the ratio of the $c\overline{c}$ and $b\overline{b}$ cross sections. In all cases we obtain a ratio close to 1, which is caused by the condition on the minimal jet transverse momentum ($p_T^{\text{jet}}>20\mathrm{GeV}$) introduced in the experiment, that makes the role of the heavy-quark mass almost negligible. The LHCb experimental ratio seems a bit larger than the theoretical predictions. We discuss potentially important for the ratio effect of $c$- or $b$-quark gluon radiative corrections related to emission outside of the jet cone. The found effect seems rather small. A more refined calculation requires full simulation of $c$ and $b$ jets, which goes beyond of the scope of this paper.

We consider the production of $Z$ bosons associated with heavy (charm and beauty) jets at the LHC energies using two scenarios based on the transverse momentum dependent (TMD) parton densities in a proton. The first of them employs the Catani-Ciafaloni-Fiorani-Marchesini gluon evolution and is implemented in the Monte Carlo event generator pegasus. Here, the heavy quarks are always produced in the hard partonic scattering. The second scheme is based on the parton branching approach, currently implemented into the Monte Carlo event generator cascade. In this scenario, the $Z+\text{jets}$ sample is generated and then events containing the heavy flavor jet in a final state are selected. We compare the predictions obtained within these two TMD-based approaches to each other, investigate their sensitivity to the TMD gluon densities in a proton, and estimate the effects coming from parton showers and double parton scattering mechanism. Additionally, we compare our predictions with the results of traditional (collinear) pQCD calculations performed at NLO accuracy. It is shown that the TMD-based results agree with the LHC experimental data collected at $\sqrt{s}=8$ and 13 TeV. We discuss the sensitivity of observables to the quark distributions in a proton and present predictions to search for the intrinsic charm signal in forthcoming analyses of the LHC experimental data.

The pion scalar, vector, and tensor form factors are calculated within a symmetry-preserving contact interaction model (CI) of quantum chromodynamics (QCD), encompassed within a Dyson-Schwinger and Bethe-Salpeter equations approach. In addition to the traditional rainbow-ladder truncation, a modified interaction kernel for the Bethe-Salpeter equation is adopted. The implemented kernel preserves the vector and axial-vector Ward-Takahashi identities, while also providing additional freedom. Consequently, new tensor structures are generated in the corresponding interaction vertices, shifting the location of the mass poles appearing in the quark-photon and quark tensor vertex and yielding a notorious improvement in the final results. Despite the simplicity of the CI, the computed form factors and radii are compatible with recent lattice QCD simulations.

The long-standing prediction of the Standard Model of elementary particles is that asymmetric neutrino environments cause rotation of linear polarization of electromagnetic wave—the birefringence. We demonstrate that this effect is strongly enhanced if additionally the photon is propagating through refractive medium, which effectively increases the photon exposure to the neutrino medium. Our estimate for an infrared laser beam in 1 m long optical fiber exposed to reactor antineutrino flux results in linear polarization rotation by the angle $\sim 4.6\times {10}^{-39}\mathrm{rad}$. We also derive the proper dependence of the effect on the angle between the directions of photon and neutrino propagation in the laboratory frame. For that purpose, we derive the correct form of the basis of polarization four-vectors, which differs from the one widely used in literature. We also estimate the subleading optical effect of the neutrino medium due to the neutrino dipole magnetic moment, in terms of a variation of the refractive index and its angular dependence. A rough monochromatic approximation points toward the existence of a resonant enhancement of the effect.

Searches for new physics often face unknown backgrounds, causing false detections or weakened upper limits. This paper introduces the “deficit hawk” technique, which mitigates unknown backgrounds by testing multiple options for data cuts, such as fiducial volumes or energy thresholds. Combining the power of likelihood ratios with the robustness of the interval-searching techniques, deficit hawks could improve mean upper limits on new physics by a factor 2 for experiments with partial or speculative background knowledge. Deficit hawks are well suited to analyses that use machine learning or other multidimensional discrimination techniques and can be extended to permit discoveries in regions without unknown background.

We present the first fully nonlinear study on the accretion of scalar fields onto a seed black hole in anti–de Sitter spacetime in Einstein-Maxwell-scalar theory. Intrinsic critical phenomena in the dynamical transition between bald and scalarized black holes are disclosed. In scalarizations, the transition is discontinuous and a metastable black hole acts as an attractor at the threshold. We construct a new physical mechanism to dynamically descalarize an isolated scalarized black hole. The first results on critical phenomena in descalarizations are revealed. The dynamical descalarizations can be either discontinuous or continuous at the threshold, distinguished by whether or not an intermediate attractor appears.

We analyze the vacuum structure of $\mathcal{N}=3,D=4$ supergravity coupled to 9 vector multiplets with gauge group $\mathrm{SO}(3)\times \mathrm{SU}(3)$. Aside from the central $\mathcal{N}=3$ ${\mathrm{AdS}}_4$ vacuum at the origin, on which the supermultiplet structure reproduces the massless sector of M theory compactified on ${\mathrm{N}}^{0,1,0}$, we find a rich structure of ${\mathrm{AdS}}_4$ vacua preserving $\mathcal{N}=0$, 1, 2, 3 supersymmetry. These new vacua are arranged in a manifold spanned by scalar fields corresponding to exactly marginal deformations of the dual CFT. This manifold has the form $T^3/K$, where $K$ is a discrete subgroup of the gauge group: $\mathcal{N}=3$, 2, and 1 vacua correspond, respectively, to a point, a line and a surface in the three-dimensional vacuum manifold. We study RG flows from the central $\mathcal{N}=3$ vacuum and elaborate on the possible higher dimensional origin of the new vacua. For the reader’s convenience we also provide a review of the embedding tensor formulation of $D=4,\mathcal{N}=3$ gauged supergravities. In particular, we provide formulas involving the fermion shift tensors and mass matrices in $\mathcal{N}=3$ theories, which can be applied to a generic gauging.

As a new step toward defining complexity for quantum field theories, we map Nielsen operator complexity for $SU(N)$ gates to two-dimensional hydrodynamics. We develop a tractable large $N$ limit that leads to regular geometries on the manifold of unitaries as $N$ is taken to infinity. To achieve this, we introduce a basis of noncommutative plane waves for the $\mathfrak{su}(N)$ algebra and define a metric with polynomial penalty factors. Through the Euler-Arnold approach we identify incompressible inviscid hydrodynamics on the two-torus as a novel effective theory of large-qudit operator complexity. For large $N$, our cost function captures two essential properties of holographic complexity measures: ergodicity and conjugate points.

We extend the method of adiabatic regularization by introducing an arbitrary parameter $\mu$ for a scalar field with quartic self-coupling in a Friedmann-Lemaître-Robertson-Walker spacetime at one-loop order. The subtraction terms constructed from this extended version allow us to define a preferred vacuum state at a fixed time $\eta ={\eta }_0$ for this theory. We compute this vacuum state for two commonly used background fields in cosmology, specially in the context of preheating. We also give a possible prescription for an adequate value for $\mu$.

Simpson and Visser recently proposed a phenomenological way to avoid some kinds of space-time singularities by replacing a parameter whose zero value corresponds to a singularity (say, $r$) with the manifestly nonzero expression $r(u)=\sqrt{u^2+b^2}$, where $u$ is a new coordinate, and $b=\text{const}>0$. This trick, generically leading to a regular minimum of $r$ beyond a black hole horizon (called a “black bounce”), may hopefully mimic some expected results of quantum gravity, and was previously applied to regularize the Schwarzschild, Reissner-Nordström, Kerr, and some other metrics. In this paper it is applied to regularize the Fisher solution with a massless canonical scalar field in general relativity (resulting in a traversable wormhole) and a family of static, spherically symmetric dilatonic black holes (resulting in regular black holes and wormholes). These new regular metrics represent exact solutions of general relativity with a sum of stress-energy tensors of a scalar field with nonzero self-interaction potential and a magnetic field in the framework of nonlinear electrodynamics with a Lagrangian function $\mathcal{L}(\mathcal{F})$, $\mathcal{F}=F_{\mu \nu }{F}^{\mu \nu }$. A novel feature in the present study is that the scalar fields involved have “trapped ghost” properties, that is, are phantom in a strong-field region and canonical outside it, with a smooth transition between the regions. It is also shown that any static, spherically symmetric metric can be obtained as an exact solution to the Einstein equations with the stress-energy tensor of the above field combination.

We reexamine the concept of the attractive gravity probe surface recently proposed as an indicator for strength of gravity. Then, we propose three new variant concepts and show refined inequalities for the four types of the attractive gravity probe surfaces by taking account of the angular momentum, gravitational waves, and matter.

We construct analytical solutions describing black holes and black strings in the Einstein $SU(N)$-nonlinear sigma model in ($3+1$) dimensions. This construction is carried out using the maximal embedding ansatz of $SU(2)$ together with the Euler parametrization of the $SU(N)$ group, in such a way that the nonlinear sigma model equations are automatically satisfied for arbitrary values of the flavor number $N$ while the Einstein equations can be solved analytically. In particular, we construct black holes with spherical and flat horizons as well as black strings that present the geometry of a three-dimensional charged Bañados-Teitelboim-Zanelli black hole on the transverse section of the string. These configurations are not trivial embeddings of $SU(2)$ into $SU(N)$, which allow us to explicitly show the role that the flavor number plays on the geometry and thermodynamics of the black holes and black strings. Finally, we perform a thermal comparison between these configurations.

We use the latest type Ia supernovae sample $\mathrm{Pantheon}+$ to explore new physics on cosmic scales. Specifically, in light of this new sample, we constrain the interacting dark energy and Hu-Sawicki $f(R)$ gravity models and employ the model-independent Gaussian processes to investigate whether there is an evidence of dark energy evolution. We find that $\mathrm{Pantheon}+$ alone just gives weak constraints. However, a data combination of $\mathrm{Pantheon}+$ with cosmic microwave background, baryon acoustic oscillations and cosmic chronometers gives a strong constraint on the interaction parameter $\epsilon =0.048\pm 0.026$, which indicates that the energy may transfer from dark energy to dark matter in the dark sector of the universe at the $1.85\sigma$ confidence level. In the meantime, we obtain a very tight constraint on the deviation from general relativity ${\log }_{10}{f}_{R0}<-6.32$ at the $2\sigma$ confidence level. Interestingly, when combining $\mathrm{Pantheon}+$ with cosmic chronometers and cosmic microwave background data, we find a quintessencelike dark energy signal beyond the $2\sigma$ confidence level in the redshift range $z\in [0.70,1.05]$. This implies the nature of dark energy may actually be dynamical.

The dark matter distribution in dwarf galaxies holds a wealth of information on the fundamental properties and interactions of the dark matter particle. In this paper, we study whether ultralight bosonic dark matter is consistent with the gravitational potential extracted from stellar kinematics. We use velocity dispersion measurements to constrain models for halo mass and particle mass. The posterior likelihood is multimodal. Particle masses of order $m\sim {10}^{-22}\mathrm{eV}$ require halos of mass in excess of $\sim {10}^{10}{M}_{\odot }$, while particle mass of order $m\gtrsim {10}^{-20}\mathrm{eV}$ are favored by halos of mass $\sim [{10}^8–{10}^9]M_{\odot }$, with a similar behavior to cold dark matter. Regardless of particle mass, the lower halo masses are allowed if stellar dynamics are influenced by the presence of a central black hole of mass at most $\sim {10}^{-2}$ the host halo mass. We find no preference for models that contain a black hole over models that do not contain a black hole. Our main conclusion is that either the fuzzy dark matter particle mass must be $m\gtrsim {10}^{-20}\mathrm{eV}$, or the Milky Way dwarfs must be unusually heavy given the expected hierarchical assembly of the Milky Way, or the Milky Way dwarfs must contain a central black hole. We find no evidence for either of the last two possibilities and consider them unlikely.

Black hole based tests of general relativity have proliferated in recent times with new and improved detectors and telescopes. Modeling of the black hole neighborhood, where most of the radiation carrying strong-field signature originates, is of utmost importance for robust and accurate constraints on possible violations of general relativity. As a first step, this paper presents the extension of general relativistic magnetohydrodynamic simulations of thin accretion disks to parametrically deformed black holes that generalize the Kerr solution. The extension is based on harmpi, a publicly available member of the harm family of codes, and uses a phenomenological metric to study parametric deviations away from Kerr. The extended model is used to study the disk structure, stability, and radiative efficiency. We also compute the Fe $\mathrm{K}\alpha$ profiles in simplified scenarios and present an outlook for the future.