We explore spontaneous $CP$ violation in the minimal non-super-symmetric $SO(10)$ grand unified theory, with a scalar sector comprising a $CP$-even $45_H$, a $126_H$, and a complex $10_H$. All renormalizable couplings are real due to $CP$ symmetry, and the Kobayashi-Maskawa phase arises solely from complex electroweak vacuum expectation values. The model requires an additional Higgs doublet fine-tuned below 500 GeV and constrains new Yukawa couplings, linking certain flavor-violating (FV) processes. Future proton decay observations may reveal correlated FV decay ratios, offering insights into minimal $SO(10)$.

The new gauge boson introduced in the minimal extension of the standard model (SM) by gauging the ${\mathrm{U}(1)}_{\mathrm{B}-\mathrm{L}}$ symmetry plays the role of dark matter when the ${\mathrm{U}(1)}_{\mathrm{B}-\mathrm{L}}$ gauge coupling is highly suppressed. This dark matter, named the Féeton dark matter is known to be efficiently created in the early Universe by inflationary fluctuations with minimal gravity coupling, hence the framework, the gauged ${\mathrm{U}(1)}_{\mathrm{B}-\mathrm{L}}$ extended $\mathrm{SM}+\text{inflation}$, solves the four major problems of the SM; neutrino masses/mixings, dark matter, baryon asymmetry of the Universe, and the initial condition of the Universe (inflation). We comprehensively study the phenomenology of the dark matter when it is heavier than the $e^{-}{e}^{+}$ threshold, namely twice the electron mass, considering the threshold effect on the dark matter decay into $e^{-}{e}^{+}$. The viable parameter region is found only in the threshold region, while the branching fraction of the decay into $e^{-}{e}^{+}$ (i.e., the $e^{-}{e}^{+}$ signal) never vanishes even at the threshold due to the effect. As a result, the pure ${\mathrm{U}(1)}_{\mathrm{B}-\mathrm{L}}$ extension without the kinetic mixing between the ${\mathrm{U}(1)}_{\mathrm{B}-\mathrm{L}}$ and hypercharge gauge bosons have already been excluded by the present observation of the 511 keV photon from the galactic center. So, the Féeton dark matter requires a nonzero kinetic mixing to be a viable dark matter candidate and will be efficiently explored by future MeV-gamma ray telescopes thanks to the nonvanishing decay process into $e^{-}{e}^{+}$.

The impact of Lorentz violating (LV) terms on the exclusive $e^{+}{e}^{-}$ production in ultraperipheral heavy-ion collisions at the Large Hadron Collider (LHC) is investigated, considering vectorial and axial couplings. Results for the differential and total cross sections are presented, and the sensitivity to a purely timelike coupling is estimated. Our results indicate that this process can improve the current upper bounds on the LV terms.

The screened massive expansion of full QCD is used in conjunction with a model for infrared quark masses to compute the Landau-gauge gluon propagator at finite temperature and baryonic density. Analytic expressions up to a one-dimensional momentum integral are provided for the propagator, and its behavior is studied at zero Matsubara frequency with respect to temperature, chemical potential, and the parameters of the expansion. The phase diagram of QCD is explored under the assumption that the deconfinement temperature can be identified as the position of the maximum of the longitudinal gluon propagator at zero Matsubara frequency and fixed spatial momentum.

Since searches for the low-lying excited baryons $\mathrm{\Xi }(1/2^{-})$ and $\mathrm{\Sigma }(1/2^{-})$ are crucial to deepening our understanding of the light baryon spectrum, we have investigated the Cabibbo-favored process ${\mathrm{\Xi }}_c^{+}\to \mathrm{\Lambda }{\overline{K}}^0{\pi }^{+}$ by taking into account the $S$-wave pseudoscalar meson-octet baryon interactions within the chiral unitary approach, which could dynamically generate the resonances $\mathrm{\Xi }(1/2^{-})$ and $\mathrm{\Sigma }(1/2^{-})$. The contributions from the excited kaons are double Cabibbo suppressed, and the contribution from the $\mathrm{\Sigma }(1385)$ is also suppressed due to Korner-Pati-Woo theory; thus, those states are expected to play negligible contributions in this process. We have predicted the ${\overline{K}}^0\mathrm{\Lambda }$ and ${\pi }^{+}\mathrm{\Lambda }$ invariant mass distributions, which have the clear signals of the $\mathrm{\Xi }(1/2^{-})$ and $\mathrm{\Sigma }(1/2^{-})$. Thus, the ${\mathrm{\Xi }}_c^{+}\to \mathrm{\Lambda }{\overline{K}}^0{\pi }^{+}$ is an ideal process to search for the low-lying baryons $\mathrm{\Xi }(1/2^{-})$ and $\mathrm{\Sigma }(1/2^{-})$, and we make a call for a precise measurements of this process in experiments, such as Belle II, LHCb, and the proposed Super Tau-Charm Facility.

There exist metastable domain walls of the flavor-singlet meson $\eta$ for the U(1) axial symmetry in two-flavor color superconductivity (2SC) in quantum chromodynamics (QCD) at large baryon density. We show that, due to the coupling of $\eta$ to confined SU(2) gluons in the 2SC phase, the effective theory on the domain wall is described by the $\mathrm{SU}(2{)}_{-1}$ Chern-Simons theory, which is dual to the $\mathrm{U}(1{)}_2$ Chern-Simons theory. This theory has a spin-1 droplet excitation that does not carry a baryon number, which we identify as a vector meson. We also discuss the effective theories and baryonic droplet excitations on the domain walls of the flavor-singlet mesons in the superfluid phases of QCD at large isospin density and two-color QCD at large baryon density.

In this work we investigate several phenomenological and technical aspects related to electroweak (EW) corrections at a high-energy muon collider, focusing on direct production processes (no vector-boson-fusion configurations). We study in detail the accuracy of the Sudakov approximation, in particular the Denner-Pozzorini algorithm, comparing it with exact calculations at next-to-leading-order EW accuracy. We also assess the relevance of resumming EW Sudakov logarithms at 3 and 10 TeV collisions. Furthermore, we scrutinize the impact of additional heavy boson radiation, namely the weak emission of $W$, $Z$, and Higgs bosons in inclusive and semi-inclusive configurations. All results are obtained via the fully automated and publicly available code madgraph5_amc@nlo.

We report measurements of production cross sections for ${\rho }^{+}$, ${\rho }^0$, $\omega$, $K^{*+}$, $K^{*0}$, $\varphi$, $\eta$, $K_S^0$, $f_0(980)$, $D^{+}$, $D^0$, $D_s^{+}$, $D^{*+}$, $D^{*0}$, and $D_s^{*+}$ in $e^{+}{e}^{-}$ collisions at a center-of-mass energy near 10.58 GeV. The data were recorded by the Belle experiment, consisting of $571{\mathrm{fb}}^{-1}$ at 10.58 GeV and $74{\mathrm{fb}}^{-1}$ at 10.52 GeV. Production cross sections are extracted as a function of the fractional hadron momentum $x_p$. The measurements are compared to pythia Monte Carlo generator predictions with various fragmentation settings, including those that have increased fragmentation into vector mesons over pseudoscalar mesons. The cross sections measured for light hadrons are consistent with no additional increase of vector over pseudoscalar mesons. The charmed-meson cross sections are compared to earlier measurements—when available—including older Belle results, which they supersede. They are in agreement before application of an improved initial-state radiation correction procedure that causes slight changes in their $x_p$ shapes.

We construct a new infinite family of integrable deformations of the principal chiral model (PCM) parametrized by an interaction function of several variables, which extends the formalism of [C. Ferko and L. Smith, An infinite family of integrable sigma models using auxiliary fields, Phys. Rev. Lett. 133, 131602 (2024).] and includes deformations of the PCM by functions of both the stress tensor and higher-spin conserved currents. We show in detail that every model in this class admits a Lax representation for its equations of motion, and that the Poisson bracket of the Lax connection takes the Maillet form, establishing the existence of an infinite set of Poisson-commuting conserved charges. We argue that the non-Abelian T-dual of any model in this family is classically integrable, and that T-duality “commutes” with a general deformation in this class, in a sense which we make precise. Finally, we demonstrate that these higher-spin auxiliary field deformations can be extended to accommodate the addition of a Wess-Zumino term, and we exhibit the Lax connection in this case.

We consider the transition rate of a freely falling Unruh-DeWitt detector, coupled linearly to a massless scalar quantum field prepared in the Hartle-Hawking-Israel state, as a probe of the interior of a black hole. Specifically, we consider the transition rate of a detector in the spinless Bañados-Teitelboim-Zanelli (BTZ) black hole as it freely falls toward and across the horizon and compare it to the corresponding situation for an $\mathbb{R}{\mathrm{P}}^2$ geon. Both the BTZ black hole and its geon counterpart are quotients of ${\mathrm{AdS}}_3$ spacetime that are identical exterior to the horizon but have different interior topologies. We find outside the horizon that the rates are qualitatively similar, but with the amplitude in the geon spacetime larger than in the BTZ case. Once the detector crosses the horizon, there are notable distinctions characterized by different discontinuities in the temporal derivative of the response rate. These discontinuities can appear outside the horizon if the detector is switched on at a sufficiently early time, within the past white hole horizon. In general, the detector can act as an “early warning system” that both spots the black hole horizon and discerns its interior topology.

Erasing a black hole leaves spacetime flat, so light passing through the region before any star forms and after the black hole’s evaporation shows no time delay, just like a flying mirror that returns to its initial starting point. Quantum radiation from a round-trip flying mirror has not been solved despite the model’s mathematical simplicity and physical clarity. Here, we solve the particle creation from worldlines that asymptotically start and stop at the same spot, resulting in interesting spectra and symmetries, including the time dependence of thermal radiance associated with Bose-Einstein and Fermi-Dirac Bogoliubov coefficients. Fourier analysis, intrinsically linked to the Bogoliubov mechanism, shows that a thermal Bogoliubov distribution does not describe the spin-statistics of the quantum field.

The linear solution for quadrupolar perturbations around de Sitter spacetime was recently constructed. In this paper, we provide the flux-balance laws for each background symmetry (dilatations, rotations, spatial translations and cosmological boosts) in terms of source moments at quadrupolar order. We write the dilatation flux-balance law in two distinct ways, which allows to contrast two distinct proposals for the negative definite energy flux. The standard Poincaré flux-balance laws at future null infinity are recovered in the flat limit of the $SO(1,4)$ flux-balance laws.

We study the Solar System constraints on covariant $f(Q)$ gravity. The covariant $f(Q)$ theory is described by the metric and affine connection, where both the torsion and curvature vanish. Considering a model including a higher nonmetricity-scalar correction, $f(Q)=Q+\alpha Q^n-2\mathrm{\Lambda }$, we derive static and spherically symmetric solutions, which represent the Schwarzschild–de Sitter solution with higher-order corrections, for two different Ansätze of the affine connection. On the obtained spacetime solutions, we investigate the perihelion precession, light deflection, Shapiro delay, Cassini constraint, and gravitational redshift in the $f(Q)$ gravity. We place bounds on the parameter $\alpha$ with $n=2$, 3 in our model of $f(Q)$ gravity, using various observational data in the Solar System.

The ringdown phase of a gravitational wave (GW) signal from a binary black hole merger provides valuable insights into the properties of the final black hole and serves as a critical test of general relativity in the strong-field regime. A key aspect of this investigation is to determine whether the first overtone mode exists in real GW data, as its presence would offer significant implications for our understanding of general relativity under extreme conditions. To address this, we conducted a reanalysis of the ringdown signal from GW150914, using the newly proposed $\mathcal{F}$-statistic method to search for the first overtone mode. Our results are consistent with those obtained through classical time-domain Bayesian inference, indicating that there is no evidence of the first overtone mode in the ringdown signal of GW150914. However, our results show the potentiality of utilizing the $\mathcal{F}\text{-statistic}$ methodology to unearth nuanced features within GW signals, thereby contributing novel insights into BH properties.

We study regular Schwarzschild black holes in general relativity as an alternative to the singular counterpart. We analyze two types of solutions which are completely parametrized by the Arnowitt–Deser–Misner mass alone. We find that both families of regular solutions contain a de Sitter condensate at the core and admit (quasi) extremal black hole configurations in which the two horizons are arbitrarily close. Cosmological models based on these regular configurations are also analyzed, finding that they describe nontrivial Kantowski-Sachs universes free of singularities.

Identifying weak gravitational wave signals in noise and estimating the source properties require high-precision waveform templates. Numerical relativity (NR) simulations can provide the most accurate waveforms. However, it is challenging to compute waveform templates in high-dimensional parameter space using NR simulations due to high computational costs. In this work, we implement a novel waveform mapping method, which is an alternative approach to the existing analytical approximations, based on closed-form continuous-time neural networks. This machine-learning-based method greatly improves the efficiency of calculating waveform templates for arbitrary source parameters, such as the binary mass ratio and the spins of component black holes. Based on this method, we present BHP2NRMLSur, a class of models (including nonspinning and spin-aligned ones) that maps point-particle black hole perturbation theory waveforms into NR and surrogate waveforms. The nonspinning model provides highly accurate waveforms that match the NR waveforms to the level of $\gtrsim 0.995$. The spin-aligned model reduces the required input parameters and hence improves the efficiency of the waveform generation—it takes a factor of $\sim 50$ less time than existing NR surrogate models to generate 100,000 waveforms, with a mismatch of $<0.01$ compared to the NR waveforms from the Simulating eXtreme Spacetimes collaboration.

This paper revisits black hole solutions surrounded by clouds and fluids of strings within the framework of general relativity. We introduce a generalized equation of state for a fluid of strings with a variable parameter and derive a general solution to Einstein field equations for this system. We allow the parameter $\alpha$ in the equation of state for a fluid of strings ($\rho /p=\alpha$) to vary as a function of the radial coordinate. A particular solution with $M=0$ is explored, focusing on positive ranges of the equation of state parameter in analogy with the reduced Kiselev solution. Furthermore, we present a novel regular black hole solution that reduces to the Schwarzschild solution with a cloud of strings when the radial coordinate is much larger than a control parameter $r_0$. As an additional contribution of this work, we show that the energy-momentum tensor for the fluid of strings can be decomposed into contributions from three components: an isotropic perfect fluid, an electromagnetic field, and a scalar field minimally coupled. The paper examines the connection between the fluid of strings and Kiselev anisotropic fluid, revealing structural similarities through their energy-momentum tensors. The study also highlights how the obtained solutions influence the horizons and thermodynamic properties of black holes. The new solutions allow for the emergence of geometries with multiple horizons and nontrivial temperature behaviors. As an additional test of the general solution, it is shown that particular choices for the function $\alpha (r)$ reproduce well-known results in the literature. Finally, we study geodesic motion of particles, geodesic completeness and shadows in the geometry of the novel regular black hole.

Using the functional renormalization group approach, we construct effective quantum spacetime geometries by self-consistently deforming the classical Schwarzschild–de Sitter black hole solution. This involves studying how quantum corrections, driven by the running of the Newton’s and cosmological constants, modify the solution across the infrared and ultraviolet regimes. We show that these quantum modifications replace the Schwarzschild singularity with a milder conical one. Moreover, two new features emerge in the ultraviolet regime. First, we identify a phase transition between anti-de Sitter/de Sitter spacetime occurring when the object’s mass exceeds a first critical threshold. Second, we predict the formation of horizons once the object’s mass exceeds a second threshold. Both thresholds are of the order of the Planck mass. Finally, we investigate the role of the anomalous dimension in the conformal sector of the theory.

We present precision measurements of the bias parameters of the one-loop power spectrum model of the Lyman-$\alpha$ (Ly-$\alpha$) forest, derived within the effective field theory (EFT) of large-scale structure. We fit our model to the three-dimensional flux power spectrum measured from the ${\mathrm{ACCEL}}^2$ hydrodynamic simulations. The EFT model fits the data with an accuracy of below 2% up to $k=2h{\mathrm{Mpc}}^{-1}$. Further, we analytically derive how nonlinearities in the three-dimensional clustering of the Ly-$\alpha$ forest introduce biases in measurements of the baryon acoustic oscillations (BAOs) scaling parameters in radial and transverse directions. From our EFT parameter measurements, we obtain a theoretical error budget of $\mathrm{\Delta }{\alpha }_{\parallel }=-0.2\%$ ($\mathrm{\Delta }{\alpha }_{\perp }=-0.3\%$) for the radial (transverse) parameters at redshift $z=2.0$. This corresponds to a shift of $-0.3\%$ (0.1%) for the isotropic (anisotropic) distance measurements. We provide an estimate for the shift of the BAO peak for Ly-$\alpha$ -quasar cross-correlation measurements assuming analytical and simulation-based scaling relations for the nonlinear quasar bias parameters resulting in a shift of $-0.2\%$ ($-0.1\%$) for the radial (transverse) dilation parameters, respectively. This analysis emphasizes the robustness of Ly-$\alpha$ forest BAO measurements to the theory modeling. We provide informative priors and an error budget for measuring the BAO feature—a key science driver of the currently observing Dark Energy Spectroscopic Instrument (DESI). Our work paves the way for full-shape cosmological analyses of Ly-$\alpha$ forest data from DESI and upcoming surveys such as the Prime Focus Spectrograph, WEAVE-QSO, and 4MOST.