In the $SO(5)\times U(1)\times SU(3)$ gauge-Higgs unification in the Randall-Sundrum warped space the mixing in the $W$ couplings in the quark sector is induced by masses of $SO(5)$ singlet fermions which are responsible for splitting masses of down-type quarks from those of up-type quarks in each generation. We show that the observed Cabibbo-Kobayashi-Maskawa matrix in the $W$ couplings is reproduced within experimental errors. Further flavor-changing neutral currents in the quark sector are shown to be naturally suppressed.

We propose a novel method, called the dimension-changing transformation (dct), to compute one-loop Feynman integrals and recently introduced fixed-branch integrals to arbitrary orders in $\epsilon$. The dct relates one-loop Feynman integrals or fixed-branch integrals in a desired spacetime dimension to their corresponding quantities with auxiliary mass in any other dimension, making the expansion to high orders in $\epsilon$ highly efficient. We applied this method to several examples to demonstrate its validity and efficiency. The approach introduced in this work has been implemented in an open-source c++ package, along with several examples to demonstrate its efficiency.

We perform an updated global analysis of the known and unknown parameters of the standard three-neutrino ($3\nu$) framework, using data available at the beginning of 2025. The known oscillation parameters include three mixing angles $({\theta }_{12},{\theta }_{23},{\theta }_{13})$ and two squared mass gaps, chosen as $\delta m^2=m_2^2-m_1^2>0$ and $\mathrm{\Delta }{m}^2=m_3^2-\frac{1}{2}(m_1^2+m_2^2)$, where the discrete parameter $\alpha =\mathrm{sign}(\mathrm{\Delta }{m}^2)$ distinguishes normal ordering (NO, $\alpha =+1$) from inverted ordering (IO, $\alpha =-1$). With respect to our previous 2021 update, the combination of accelerator, reactor, and atmospheric neutrino data leads to appreciably reduced uncertainties for ${\theta }_{23}$, ${\theta }_{13}$, and $|\mathrm{\Delta }{m}^2|$. In particular, $|\mathrm{\Delta }{m}^2|$ is the first $3\nu$ parameter to enter the domain of subpercent precision (0.8% at $1\sigma$). We underline some issues about common systematics in combined fits that might affect (and possibly weaken) this error estimate. Concerning oscillation unknowns, we find a relatively weak preference for NO versus IO (at $2.2\sigma$), for $CP$ violation versus conservation in NO ($1.3\sigma$), and for the first ${\theta }_{23}$ octant versus the second in NO ($1.1\sigma$). We discuss the current status and qualitative prospects of the mass ordering hint in the plane charted by the mass parameters $(\delta m^2,\mathrm{\Delta }{m}_{ee}^2)$, where $\mathrm{\Delta }{m}_{ee}^2=|\mathrm{\Delta }{m}^2|+\frac{1}{2}\alpha ({\cos }^2{\theta }_{12}-{\sin }^2{\theta }_{12})\delta m^2$, to be jointly measured by the JUNO experiment with subpercent precision. We also discuss upper bounds on nonoscillation observables, including the effective ${\nu }_e$ mass $m_{\beta }$ in $\beta$ decay, the effective Majorana mass $m_{\beta \beta }$ in $0\nu \beta \beta$ decay, and the sum of neutrino masses $\mathrm{\Sigma }$ in cosmology. We adopt $m_{\beta }<0.50\mathrm{eV}$ $(2\sigma )$ from current ${}^3\mathrm{H}$ data and report $m_{\beta \beta }<0.086\mathrm{eV}$ ($2\sigma$) from a combined ${}^{76}\mathrm{Ge}$, ${}^{130}\mathrm{Te}$, and ${}^{136}\mathrm{Xe}$ data analysis, accounting for parametrized nuclear matrix element covariances. Concerning $\mathrm{\Sigma }$, current results show tensions within the standard $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) cosmological model, pulling $\mathrm{\Sigma }$ toward unphysical values and suggesting possible model extensions. We discuss representative combinations of data, with or without augmenting the $\mathrm{\Lambda }\mathrm{CDM}$ model with extra parameters accounting for possible systematics (lensing anomaly) or new physics (dynamical dark energy). The resulting $2\sigma$ upper limits are roughly spread around the bound $\mathrm{\Sigma }<0.2\mathrm{eV}$ within a factor of 3 (both up- and downward), with different implications for NO and IO scenarios. Bounds from oscillation and nonoscillation data are also discussed in the planes charted by pairs of ($m_{\beta },m_{\beta \beta },\mathrm{\Sigma }$) parameters.

We describe the dynamics of a pointlike detector modeled by a harmonic oscillator coupled to a free quantum field in a curved spacetime. We derive covariant equations of motion for a quadrature of the oscillator. We renormalize the integro-differential equation that governs its dynamics, introducing phenomenological parameters such as a dispersion coefficient and a Lamb-shift parameter. Our formal solution, expressed in terms of Green’s functions, which is essentially nonperturbative, allows for the covariant and causal analysis of locally induced observables on the field at all orders in the coupling strength. We apply this formalism to describe the detection of non-Gaussianities present in the field’s state.

We present a scheme for numerically solving Maxwell’s equations in a weakly perturbed spacetime without introducing the usual geometric optics approximation. Using this scheme, we study light propagation through a spherical perturbation of a stationary metric in the linear limit. Going beyond geometric approximation allows us to explore the wave optics effects that occur when the wavefront propagates through the gravitational potential. We find that the wavefront breaks on the gravitational potential due to the Shapiro time delay, i.e., due to the slowing down of light when propagating in an inhomogeneous spacetime. This again leads to constructive interference, resulting in a persistent frequency dependent amplification of parts of the wave amplitude. When the wave length is shorter than a certain threshold set by the induced gravitational mass, the waves are reflected on the curvature gradient.

Two quantum-corrected black hole models have recently been proposed within the Hamiltonian constraints approach to quantum gravity, maintaining general covariance [Phys. Rev. D 111, L081504 (2025).]. We have studied in detail the quasinormal spectra of test fields and axial gravitational perturbations of these black holes using various methods. The two models differ in their choice of quantum parameter $\xi$, and we can distinguish them by their quasinormal spectra. In the first model, increasing the quantum parameter results in higher real oscillation frequencies and damping rates of the fundamental mode. In contrast, the second model shows a decrease in the oscillation frequency of the least-damped mode when the quantum parameter is introduced. We have shown that, while the fundamental mode changes relatively gradually with the quantum parameter, the first few overtones deviate from their Schwarzschild limits at an increasing rate. This results in a qualitatively new behavior: the real parts of the frequencies of the first and higher overtones tend to zero as the quantum parameter increases. In addition to the branch of modes that are perturbative in the quantum parameter, we observe some nonperturbative modes at moderate values of the quantum parameter. Additionally, we have calculated the radii of the shadows cast by these black holes and discussed possible constraints based on observations of Sgt $A^{*}$. As a by-product, using the above two models of black holes and also quantum Oppenheimer-Snyder model [Phys. Rev. Lett. 130, 101501 (2023).], we tested the method of calculating quasinormal modes of this kind based on a recent parametrization of effective potentials, and showed that while the parametrized formalism could be used for estimating the fundamental mode at small values of the coupling, its accuracy is highly dependent on the particular spacetime under consideration and is insufficient even for the lowest overtones.

How do regular black holes evade the Penrose singularity theorem? Various models of stationary regular black holes globally satisfy the null convergence condition (NCC). At first glance this might seem puzzling, as the NCC must generically be violated to avoid the focusing point implied by the Penrose theorem. In fact, the Penrose singularity theorem depends on subtle global assumptions and does not provide information about where and when the singularity actually forms. In particular, inner horizons are typically reached at finite affine parameter, before null geodesic focusing occurs, and the region inside the inner horizon is not itself a trapped region. Specifically, the Bardeen-Dymnikova-Hayward models of stationary regular black holes feature an inner Cauchy horizon that violates global hyperbolicity, hence violating one of the key assumptions of Penrose’s singularity theorem and, furthermore, challenging their viability as long-living end points of gravitational collapse. In contrast, during nonstationary processes describing kinematic transitions between standard singular black holes and regular black holes or horizonless compact objects, the inner horizon—when present—need not act as a Cauchy horizon. This raises the intriguing possibility that the NCC might instead be violated during intermediate stages of such transitions. Our detailed analysis confirms that NCC violations occur frequently during such kinematic transitions, even when the stationary end point spacetimes respect the NCC. We also investigate analogous transitions toward black-bounce spacetimes and their horizonless compact counterparts, wormholes, where the NCC is always violated. These findings offer new insights into how regular black holes and related objects evade the constraints imposed by the Penrose singularity theorem.

Combining multiple events into population analyses is a cornerstone of gravitational-wave astronomy. A critical component of such studies is the assumed population model, which can range from astrophysically motivated functional forms to nonparametric treatments that are flexible but difficult to interpret. In practice, the current approach is to fit the data multiple times with different population models to identify robust features. We propose an alternative strategy: assuming the data have already been fit with a flexible model, we present a practical recipe to reconstruct the population distribution of a different model. As our procedure postprocesses existing results, it avoids the need to access the underlying gravitational-wave data again and handle selection effects. Additionally, our reconstruction metric provides a goodness-of-fit measure to compare multiple models. We apply this method to the mass distribution of black-hole binaries detected by LIGO/Virgo/KAGRA. Our work paves the way for streamlined gravitational-wave population analyses by first fitting the data with advanced nonparametric methods and careful handling of selection effects, while the astrophysical interpretation is then made accessible using our reconstruction procedure on targeted models. The key principle is that of conceptually separating data description from data interpretation.

We investigate the phenomenon of entanglement harvesting for a spacetime in quantum superposition, using two Unruh-DeWitt detectors interacting with a quantum scalar field where the spacetime background is modeled as a superposition of two quotient Minkowski spaces which are not related by diffeomorphisms. Our results demonstrate that the superposed nature of spacetime induces interference effects that can significantly enhance entanglement for both twisted and untwisted field. We compute the concurrence, which quantifies the harvested entanglement, as function of the energy gap of detectors and their separation. We find that it reaches its maximum when we condition the final spacetime superposition state to match the initial spacetime state. Notably, for the twisted field, the parameter region without entanglement exhibits a significant deviation from that observed in classical Minkowski space or a single quotient Minkowski space.

During inflation, an axion field coupled to a gauge field through a Chern-Simons term can trigger the production of gauge quanta due to a tachyonic instability. The amplification of the gauge field modes exponentially depends on the velocity of the axion field, which in turn slows down the rolling of the axion field when backreaction is taken into account. To illustrate how the strength of the Chern-Simons coupling and the slope of the axion potential influence the particle production, in this paper we consider a toy model in which the axion field is a spectator with a linear potential. In the strong backreaction regime, the energy density of the gauge field quasiperiodically oscillates. The steep slope of the axion potential linearly increases the peak amplitude of the energy density while the strong coupling linearly decreases the peak amplitude. Additionally, we calculate the energy spectrum of gravitational waves.

If a cosmological first-order phase transition occurs sufficiently slowly, delayed vacuum decay may lead to the formation of primordial black holes. Here we consider a simple model as a case study of how the abundance of the produced black holes depends on the model’s input parameters. We demonstrate, using both numerical and analytical arguments and methods, that the black hole abundance is controlled by a double, “super”-exponential dependence on the three-dimensional Euclidean action over temperature at its minimal value. We show that a modified expansion rate during the phase transition, such as one driven by an additional energy density component, leads to a weaker dependence on the underlying model parameters, but maintains the same superexponential structure. We argue that our findings generalize to any framework of black hole production via delayed vacuum decay.

Nonadiabatic production of massive particles is a generic feature of many inflationary mechanisms. If sufficiently massive, these particles can leave features in the cosmic microwave background (CMB) that are not well-captured by traditional correlation function analyses. We consider a scenario in which particle production occurs only in a narrow time interval during inflation, eventually leading to CMB hot or cold spots with characteristic shapes and sizes. Searching for such features in CMB data is analogous to searching for late-Universe hot or cold spots, such as those due to the thermal Sunyaev-Zel’dovich (tSZ) effect. Exploiting this data-analysis parallel, we perform a search for particle-production hot spots in the Planck PR4 temperature dataset, which we implement via a matched-filter analysis. Our pipeline is validated on synthetic observations and found to yield unbiased constraints on sufficiently large hot spots across $\approx 60\%$ of the sky. After removing point sources and tSZ clusters, we find no evidence for new physics and place novel bounds on the coupling between the inflaton and massive particles. These bounds are strongest for larger hot spots, produced early in inflation, whilst sensitivity to smaller hot spots is limited by noise and beam effects. Through such methods, we can constrain particles with masses $\mathcal{O}(100)$ times larger than the inflationary Hubble scale, which represents possibly the highest energies ever directly probed with observational data.

This paper presents a kinetic model for the coupled evolution of radiation, electrons, and ions in a radiation plasma system. The model is solved using two methods. The gas-kinetic scheme (GKS) for electron and ion hydrodynamics and the unified gas-kinetic scheme (UGKS) for nonequilibrium radiative transfer. The UGKS accurately captures multiscale photon transport from free streaming to diffusion across varying fluid opacities. This approach enables the scheme to model equilibrium plasma with nonequilibrium radiation transport. The model is validated through several test cases, including radiative transfer in kinetic and diffusion regimes, Marshak wave, radiative shock, three-temperature double lax shock tube problem, two-dimensional Sedov blast wave, and two-dimensional top hat based problem. These tests demonstrate the current scheme’s capability to handle diverse radiation plasma scenarios.

We present a novel method that enables us to estimate the acceleration of individual millisecond pulsars (MSPs) using only their spin period and its time derivative. For our binary MSP sample, we show that one can obtain an empirical calibration of the magnetic braking term that relies only on observed quantities. We find that such a model for magnetic braking is only valid for MSPs with small surface magnetic field strengths ($<3\times {10}^8\mathrm{G}$) and large characteristic ages ($>5\times {10}^9\mathrm{yrs}$). With this method, we are able to effectively double the number of pulsars with line-of-sight acceleration measurements, from 27 to 53 sources. This expanded dataset leads to an updated measurement of the total density in the midplane, which we find to be ${\rho }_0=0.108\pm 0.008\mathrm{stat}\pm 0.011\mathrm{sys}{M}_{\odot }/{\mathrm{pc}}^3$, and the first $>3\sigma$ measurement of the local dark matter density, which we calculate to be ${\rho }_{0,\mathrm{DM}}=0.0098\pm 0.0025\mathrm{stat}\pm 0.0003\mathrm{sys}{M}_{\odot }/{\mathrm{pc}}^3$ ($0.37\pm 0.10\mathrm{GeV}/{\mathrm{cm}}^3$). This updated value for ${\rho }_{0,\mathrm{DM}}$ is in good agreement with literature values derived from kinematic estimates. The pulsar accelerations are very asymmetric above and below the disk; we show that the shape and size of this asymmetry can be largely explained by the north-south asymmetry of disk star counts and the offset in the Milky Way disk and halo centers of mass due to the Large Magellanic Cloud.

We extend our previous work on a novel class of unstable qubits which we have identified recently and called them critical unstable qubits (CUQs). The characteristic property of CUQs is that the energy-level and decay-width vectors, $\mathbf{E}$ and $\mathbf{\Gamma }$, are orthogonal to one another, and the key parameter $r=|\mathbf{\Gamma }|/|2\mathbf{E}|$ is less than 1. Most remarkably, CUQs exhibit two atypical behaviors: (i) they display coherence-decoherence oscillations in a co-decaying frame of the system described by a unit Bloch vector $\mathbf{b}$, and (ii) the unit Bloch vector $\mathbf{b}$ describing a pure CUQ sweeps out unequal areas during equal intervals of time, while rotating about the vector $\mathbf{E}$. The latter anharmonic phenomenon emerges beyond the usual oscillatory pattern due to the energy-level difference of the two-level quantum system, which governs an ordinary qubit. By making use of a Fourier series decomposition, we define anharmonicity observables that quantify the degree of nonsinusoidal oscillation of a CUQ. We apply the results of our formalism to the $B^0{\overline{B}}^0$-meson system and derive, for the first time, generic upper limits on these new observables.

Laboratory searching for dark matter is crucial for understanding several fundamental conundrums in physics and cosmology. Most cavity-based haloscope searches focus on the frequency range below 10 GHz, while the parameter space with higher frequency remains rarely explored, due to the challenges lying in the fabrication of microwave cavities. Here we report the first Q band haloscope searching for dark photons with a 33.141 GHz cavity. A novel coupling tuning structure separated from the cavity was designed so as not to degrade the quality factor of the cavity. We have established the most stringent constraints $\chi <2.5\times {10}^{-12}$ at a confidence level of 90% in the frequency range from 33.139 to 33.143 GHz, corresponding to the mass of dark photons ranging from 137.05 to $137.07\mathrm{\mu }\mathrm{eV}$. The results surpass the previous astronomical constraints by nearly three orders of magnitude. This work has demonstrated the feasibility of dark matter haloscopes in the Q band. In the future, the constraints can be further improved by more than one order of magnitude through low-temperature experiments, and the setup can be extended to search for axions, axion-like particles, and high-frequency gravitational waves.

In this work, we use published results by the ATLAS Collaboration collected at LHC Run 2 at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ with an integrated luminosity of $139{\mathrm{fb}}^{-1}$ to derive lower-mass limits on the $Z^{\prime }$ gauge boson associated with the $B-L$ gauge symmetry. Using dilepton data, we find that $M_{Z^{\prime }}>4\mathrm{TeV}$ (6 TeV) for $g_{B-L}=0.1$ ($g_{B-L}=0.5$) in the absence of invisible decays. Once invisible decays are turned on, these limits are substantially relaxed. Assuming an invisible branching ratio of ${\mathrm{BR}}_{\mathrm{inv}}=0.9$, the LHC bound is loosened up to $M_{Z^{\prime }}>4.8\mathrm{TeV}$ for $g_{B-L}=0.5$. This analysis confirms that the LHC is able to impose stricter constraints than the bounds established by experiments at LEP. We also estimate the projected High-Luminosity LHC bounds at $\sqrt{s}=14\mathrm{TeV}$ and a planned integrated luminosity of $\mathcal{L}=3{\mathrm{ab}}^{-1}$ that will probe $Z^{\prime }$ masses up to 7.5 TeV.

Working in the hybrid framework of the high energy $pA$ collisions we identify a new contribution to transverse single spin asymmetry (SSA). The phase necessary for the SSA is provided by the Pomeron-odderon interference in the dense nuclear target. The complete formula for the $pA\to hX$ polarized cross section also contains the transversity distribution for the polarized projectile as well as the real part of the twist-three fragmentation function. We numerically estimate the asymmetry $A_N$ and its nuclear dependence. Based on a model computation we find that $A_N$ can be a percent level in the forward and low-$P_{h\perp }$ region. For large nuclei we find significant suppression, with $A_N\propto A^{-7/6}$ parametrically. As a notable feature we find a node of $A_N$ as a function of the $P_{h\perp }$ around the values of the initial saturation scale that could be used to test this mechanism experimentally.

Dense quantum chromodynamics (QCD) matter may exhibit crystalline phases. Their existence is reflected in a moat regime, where mesonic correlations feature spatial modulations. We study the real-time properties of pions at finite temperature and density in QCD in order to elucidate the nature of this regime. We show that the moat regime arises from particle-hole-like fluctuations near the Fermi surface. This gives rise to a characteristic peak in the spectral function of the pion at nonzero spacelike momentum. This peak can be interpreted as a new quasi particle, the moaton. In addition, our framework also allows us to directly test the stability of the homogeneous chiral phase against the formation of an inhomogeneous condensate in QCD. We find that an inhomogeneous instability is highly unlikely for baryon chemical potentials ${\mu }_B\le 630\mathrm{MeV}$.