The minimal $SO(10)$ grand unified theory, augmented by higher-dimensional operators, is based on the following Higgs representations: adjoint $45_{\mathrm{H}}$, spinor $16_{\mathrm{H}}$, and complex vector $10_{\mathrm{H}}$. It was recently realized that, as opposed to the conventional wisdom, any intermediate mass scale has to lie close to the grand unification one. This bears profound consequences for the scalar particles mass spectrum and the proton decay lifetime. A complete analysis of the parameter space shows the following interesting correlation under the requirement of perturbativity of the theory: a color octet below approximately 5 TeV would imply a lower bound on neutrino mass $m_{\nu }\gtrsim 0.2\mathrm{eV}$, soon to be probed; a scalar weak triplet below 500 GeV; and a scalar-like quark below 3 TeV. If one were to stick to no flavor cancellations in proton decay amplitudes, one would recover a recent result of all these states being accessible at collider energies. Moreover, the proton decay lifetime would then be tantalizingly close to the present experimental bound.

We revisit the generalized two-Higgs-doublet model (2HDM) with a minimally perturbed lepton specific (Type-X) Yukawa sector in context of the muon collider. The model offers a large region of parameter space where it can provide a solution to the observed muon ($g-2$) excess. Specifically the low mass $CP$ odd scalar of this model plays an important role to fit this anomaly. Interestingly, the coupling of the pseudoscalar with the muons is proportional to $\tan \beta$ (which equals to the ratio of vacuum expectation values of the Higgs doublets) which dominantly controls the one loop and two loop contributions of the muon magnetic moment, therefore it can be probed directly at a muon collider with greater sensitivity in comparison to the Large Hadron Collider. Primarily focusing on a parameter space where muon $g-2$ anomaly is satisfied, we explore the available theoretical and experimental constraints arising from vacuum stability, unitarity, lepton flavor violation, electroweak precision constraint, B-meson decay, and collider experiments on the model. In the parameter space where all these constraints are satisfied, we propose to study the production of the light pseudoscalar $A$ in association with a photon at a 3 TeV muon collider. Subsequent decay of $A$ into a $\tau$ pair will produce a striking $l^{+}{l}^{-}\gamma$ plus missing energy signature.

We discuss multi-$Z^{\prime }$ signatures coming from decays of Higgs bosons in models with a spontaneously broken $U(1{)}^{\prime }$ symmetry, which can be observed as “lepton jets” or multilepton final states depending on the mass range of new bosons. We consider anomaly-free $U(1{)}^{\prime }$ models without introducing new fermions except for right-handed neutrinos, in which the Higgs sector is composed of an isospin doublet and a singlet fields with zero and nonzero $U(1{)}^{\prime }$ charges, respectively. The multi-$Z^{\prime }$ signatures can then be obtained via the decays of the discovered (extra) Higgs boson $h$ ($\varphi$), i.e., $h\to Z^{\prime }{Z}^{\prime }$, $\varphi \to Z^{\prime }{Z}^{\prime }$, and/or $h\to \varphi \varphi \to 4Z^{\prime }$ as far as kinematically allowed. We give the upper limit on the branching ratios of $h$ into $Z^{\prime }{Z}^{\prime }$ and $4Z^{\prime }$ from the current experimental data in each model. We also show the deviation in the $hhh$ coupling from the standard model prediction at one-loop level, and find that its amount is typically smaller than 1%.

We study the diffusion properties of an interacting hadron gas and evaluate the diffusion coefficient matrix for the baryon, strange, electric, and charm quantum numbers. For the first time, this study sheds light on the charm current and estimates the diffusion matrix coefficient for the charmed states by treating them as a part of the quasithermalized medium. We explore the diffusion matrix coefficient as a function of temperature and center-of-mass energy. A van der Waals–like interaction is assumed between the hadrons, including attractive and repulsive interactions. The calculation of diffusion coefficients is based on relaxation time approximation to the Boltzmann transport equation. A good agreement with available model calculations is observed in the hadronic limit. To conclude the study, we discuss, with a detailed explanation, that charm fluctuation is expected to be a better tool for probing the QCD critical point.

Representing the parton distribution functions (PDFs) of the proton and other hadrons through flexible, high-fidelity parametrizations has been a long-standing goal of particle physics phenomenology. This is particularly true since the chosen parametrization methodology can play an influential role in the ultimate PDF uncertainties as extracted in QCD global analyses; these, in turn, are often determinative of the reach of experiments at the LHC and other facilities to nonstandard physics, including at large $x$, where parametrization effects can be significant. In this study, we explore a series of encoder-decoder machine-learning (ML) models with various neural-network topologies as efficient means of reconstructing PDFs from meaningful information stored in an interpretable latent space. Given recent effort to pioneer synergies between QCD analyses and lattice-gauge calculations, we formulate a latent representation based on the behavior of PDFs in Mellin space, i.e., their integrated moments, and test the ability of various models to decode PDFs from this information faithfully. We introduce a numerical package, PDFdecoder, which implements several encoder-decoder models to reconstruct PDFs with high fidelity and use this end-to-end tool to explore how such neural-network-based models might connect PDF parametrizations to underlying properties like their Mellin moments. We additionally dissect patterns of learned correlations between encoded Mellin moments and reconstructed PDFs that suggest opportunities for further improvements to ML-based approaches to PDF parametrizations and uncertainty quantification.

The interference between the atmospheric and solar neutrino oscillation subamplitudes is said to be responsible for $CP$ violation (CPV) in neutrino appearance channels. More precisely, CPV is generated by the interference between the parts of the neutrino oscillation amplitude that are $CP$ even and $CP$ odd: even or odd when the neutrino mixing matrix is replaced with its complex conjugate. This is the CPV interference term, as it gives a contribution to the oscillation probability, the square of the amplitude, which is opposite in sign for neutrinos and antineutrinos and is unique. For this interference to be nonzero, at least two subamplitudes are required. There are, however, other interference terms, which are even under the above exchange, and these are the $CP$ conserving (CPC) interference terms. In this paper, we explore in detail these CPC interference terms and show that they cannot be uniquely defined, as one can move pieces of the amplitude from the atmospheric subamplitude to the solar subamplitude and vice versa. This freedom allows one to move the CPC interference terms around, but does not let you eliminate them completely. We also show that there is a reasonable definition of the atmospheric and solar subamplitudes for the appearance channels such that in neutrino disappearance probability there is no atmospheric-solar CPC interference term. However, with this choice, there is a CPC interference term within the atmospheric sector.

Studies are performed of the Cabibbo-favored decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{K}^{+}$ and the singly Cabibbo-suppressed decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{\pi }^{+}$, based on a sample of $e^{+}{e}^{-}$ collision data, corresponding to an integrated luminosity of $4.5{\mathrm{fb}}^{-1}$, accumulated at center-of-mass energies between 4599.53 MeV and 4698.82 MeV with the BESIII detector. The decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{\pi }^{+}$ is observed for the first time. The branching fractions of ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{K}^{+}$ and ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{\pi }^{+}$ are measured to be $(3.04\pm 0.30\pm 0.16)\times {10}^{-3}$ and $(1.73\pm 0.27\pm 0.10)\times {10}^{-3}$, respectively, where the first uncertainties are statistical and the second are systematic. These results correspond to the most precise measurement of these quantities for both decays. Evidence of a $K^{*+}$ contribution in the ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}_S^0{\pi }^{+}$ decay is found with a statistical significance of $4.71\sigma$. The branching fraction of ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{K}^{*+}$ is calculated under three possible interference scenarios, with the significance increasing to $5.03\sigma$ when interference is taken into account.

Tests of quantum properties of fundamental particles in high energy colliders are starting to appear. Entanglement and Bell inequality violation in top and antitop quark system is of particular interest since top quarks are unstable particles that undergo a cascade decay. We argue for criteria for the spacelike separation between top and antitop quarks at their different decay stages. We considered causal separation at three different instances: at the top quark decay, at the $W$ boson decay, and at the lepton/jet contact with the macroscopic apparatus. We showed that the spacelike fraction of events is the smallest, when requiring that both top quarks and $W$ bosons decay within the spacelike interval. For high invariant masses, typically required for the Bell inequality violation, this is almost identical to just the top quark decay requirement. We also include an option for the angular correlation of the $b$ quarks from top quark decay to be used for the spin correlation measurement. We require that both top quark and $b$ hadron decays are spacelike separated. Again, we find that at high invariant masses it is almost identical to just the requirement of spacelike separation between top and antitop quarks. We provide numerical values for our proposed criteria. If such a criterion is satisfied, the system is guaranteed to not be in a causal connection.

A combination of searches for the single production of vectorlike top quarks ($T$) is presented. These analyses are based on proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ recorded in 2015–2018 with the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of $139{\mathrm{fb}}^{-1}$. The $T$ decay modes considered in this combination are into a top quark and either a Standard Model Higgs boson or a $Z$ boson ($T\to Ht$ and $T\to Zt$). The individual searches used in the combination are differentiated by the number of leptons ($e$, $\mu$) in the final state. The observed data are found to be in good agreement with the Standard Model background prediction. Interpretations are provided for a range of masses and couplings of the vectorlike top quark for benchmark models and generalized representations in terms of 95% confidence level limits. For a benchmark signal prediction of a vectorlike top quark SU(2) singlet with electroweak coupling, $\kappa$, of 0.5, masses below 2.1 TeV are excluded, resulting in the most restrictive limits to date.

We searched for violations of the weak equivalence principle using a cryogenic torsion balance with a pendulum comprised of superconducting niobium and copper. We constrain the Eötvös parameter with 95% confidence to ${\eta }_{{\mathrm{Nb}}^{*}\text{−}\mathrm{Cu}}\le 2.0\times {10}^{-9}$ and ${\eta }_{\mathrm{CP}\text{−}\mathrm{ee}}\le 9.2\times {10}^{-4}$ for superconducting niobium and Cooper pairs, respectively.

One quantum characterization of a black hole motivated by (local) holography and thermodynamics is that it maximizes thermodynamic entropy for a given surface area. In the context of quantum gravity, this could be more fundamental than the classical characterization by a horizon. As a step, we explore this possibility by solving the 4D semiclassical Einstein equation with many matter fields. For highly excited spherically symmetric static configurations, we apply local typicality and estimate the entropy including self-gravity to derive its upper bound. The saturation condition uniquely determines the entropy-maximized configuration: self-gravitating quanta condensate into a radially uniform dense configuration with no horizon, where the self-gravity and a large quantum pressure induced by the curvatures are balanced and no singularity appears. The interior metric is a self-consistent and nonperturbative solution in Planck’s constant. The maximum entropy, given by the volume integral of the entropy density, agrees with the Bekenstein-Hawking formula through self-gravity, deriving the Bousso bound for thermodynamic entropy. Finally, 10 future prospects are discussed, leading to a speculative view that the configuration represents a quantum-gravitational condensate in a semiclassical manner.

We study six-dimensional $F(4)$ gauged supergravity coupled to four vector multiplets with a non-semisimple $ISO(3)\times U(1)$ gauge group. This gauged supergravity arises from a consistent truncation of type IIB string theory on $S^2\times \mathrm{\Sigma }$ with $\mathrm{\Sigma }$ being a Riemann surface. We find that the gauged supergravity admits two $SO(3)$ symmetric ${\mathrm{AdS}}_6$ vacua, one with $N=(1,1)$ supersymmetry and the other one as non-supersymmetric. We compute all scalar masses at these critical points and find that only the supersymmetric ${\mathrm{AdS}}_6$ vacuum is stable. By truncating to $SO(3)\times U(1)$ and $SO(2)\times U(1)$ invariant sectors, we study holographic renormalization group flow solutions from this critical point to a number of nonconformal phases of the dual $N=2$ superconformal field theories in five dimensions. Finally, we give some examples of supersymmetric Janus solutions describing conformal interfaces within the five-dimensional superconformal field theories. All of these solutions provide first holographic results from matter-coupled $F(4)$ gauged supergravity with non-semisimple gauge groups.

In this article, we examine entangled quantum probes in geodesic trajectories in a flat background with a gravitational wave (GW) burst. In particular, these quantum probes are prepared initially either in the symmetric or antisymmetric Bell’s states, and we study the radiative process as the GW burst passes. We split a generic GW burst into two profiles with and without memory. GW burst with (without) memory profiles have different (similar) asymptotic strains between early and late times. We observe that for eternal switching, there is a finite change in the collective atomic transition rate due to the memory part of the GW burst, while the contribution from the without memory counterpart vanishes. We also consider finite Gaussian switching and observe characteristic differences in the radiative process between the GW backgrounds with and without memory. Notably, if the Gaussian switching is peaked much later compared to the passing of GW, only the memory part contributes to the radiative process. Thus, although examined in a simplified setup, our findings suggest the potential to distinguish bursts with and without GW memory based on the radiative process of entangled detectors.

The expansion of the Universe in $f(R,T)$ gravity is studied. By focusing on functions of the form $f(R,T)=f_1(R)+f_2(T)$, we assert that present-day acceleration can be achieved if the functional form of $f_2(T)$ either grows slowly or falls as a function of $T$. In particular, we demonstrate that when $f_2(T)\propto T^{-1}$, the Universe transitions to exponential growth at late times, just as it does in the standard cosmological model. A comparison of predictions of this model with type Ia supernovae shows that this model fits the data as well or even slightly better than the standard cosmological model without increasing the number of parameters.

We explore the possibilities of modeling a spherically symmetric static spacetime that can emerge as the end state of gravitational collapse, by considering it to be seeded by a composite fluid made of matter and a scalar field. In this scenario, the matter represents dark matter, while the scalar field represents dark energy. On certain scales, dark energy is believed to significantly influence the structure formation of dark matter. Various models describe the possible impacts of dark energy on structure formation under different scenarios. By investigating an inhomogeneous scalar field representing dark energy, coupled with dark matter, we demonstrate that this two-component fluid can seed spacetimes forming the final equilibrium state. We derive solutions for the scalar field and potential for Joshi-Malafarina-Narayan (JMN) spacetimes.

The inspiral of a circular, nonprecessing binary exhibits an approximate helical symmetry. The effects of eccentricity, precession, and radiation reaction break the exact symmetry. We estimate the failure of this symmetry using the flux of the Bondi–van der Burg–Metzner–Sachs (BMS) charge corresponding to helical symmetry carried away by gravitational waves. We analytically compute the helical flux for binaries moving on eccentric orbits and quasicircular orbits without precession using post-Newtonian theory. The helical flux is nonvanishing at the 0PN order for eccentric orbits as expected. We analytically predict the helical flux to be at a relative 5PN order for quasicircular nonprecessing binaries. This prediction is compared with 113 quasicircular nonprecessing numerical relativity waveforms from the SXS catalog. We find good agreement between analytical and numerical results for quasicircular nonprecessing binaries establishing that helical symmetry starts to break at 5PN for these binaries.

In cosmology, when dissipative effects are minimal, the energy content of the Universe can be effectively described as a sum of perfect fluids. Perfect fluid descriptions ensure thermal equilibrium since they equilibrate immediately. However, interactions among different energy content of the Universe might prevent such rapid equilibration. This limitation calls for a more fundamental framework that incorporates these interactions directly at the level of the action. In earlier work, two of the authors demonstrated that an interacting dark energy (DE)–dark matter (DM) field theory action could be derived from a modified gravity action via a conformal transformation, establishing a one-to-one correspondence between the field theory action and fluid for a unique interaction term [Phys. Rev. D 103, 023510 (2021)]. In this work, we extend that analysis by considering quadratic order Horndeski gravity, identifying two classes of models—field coupling and field-kinetic coupling. Our approach generalizes the coupling function for DE-DM interactions by incorporating an additional dependence on kinetic terms. We establish a field-to-fluid mapping for dark matter and find that this mapping only holds for a specific form of the interaction strength. Interestingly, we show that this interaction strength excludes nongravitational interactions between dark energy and dark radiation. Numerical analysis reveals that purely kinetic interactions within the dark sector can significantly alter cosmological evolution compared to noninteracting scenarios, highlighting the strong dependence of cosmological dynamics on coupling strength. A preliminary examination of linear scalar perturbations indicates that the field-kinetic coupling results in a nonzero gravitational slip parameter and momentum exchange.

Gauged boson stars are exotic compact objects that can potentially mimic black holes or magnetized neutron stars in both their gravitational and electromagnetic signatures, offering a compelling new description or even an alternative explanation for various multimessenger phenomena. As a crucial step toward establishing boson stars as viable multimessenger sources, we perform 3D numerical simulations of the fully nonlinear Einstein-Maxwell-Klein-Gordon system, focusing on both spherical and axisymmetric boson star configurations that vary in their electromagnetic coupling between the neutral case up to values close to the critical case, and thus their magnetic field content. For spherical configurations, we consistently find stable solutions. In contrast, for axially symmetric, electrically neutral, magnetized configurations, the dynamics are highly sensitive to the electromagnetic coupling. Configurations with stronger coupling develop a one-armed mode instability, which leads to collapse into black holes. Configurations with weaker coupling undergo a two-stage process: an initial bar-mode instability that triggers a one-armed spiral deformation. This eventually also results in black hole formation, accompanied by emissions of both gravitational and electromagnetic radiation. A similar instability and two-stage pattern is observed in all charged rotating boson stars analyzed. However, all of these configurations become stable when self-interactions are introduced.

We present model-marginalized limits on the six standard $\mathrm{\Lambda }\mathrm{CDM}$ cosmological parameters (${\mathrm{\Omega }}_{\mathrm{c}}{h}^2$, ${\mathrm{\Omega }}_{\mathrm{b}}{h}^2$, ${\theta }_{\mathrm{MC}}$, ${\tau }_{\mathrm{reio}}$, $n_s$ and $A_s$), as well as on selected derived quantities ($H_0$, ${\mathrm{\Omega }}_{\mathrm{m}}$, ${\sigma }_8$, $S_8$ and $r_{\mathrm{drag}}$), obtained by considering several extensions of the $\mathrm{\Lambda }\mathrm{CDM}$ model and three independent cosmic microwave background (CMB) experiments: the Planck satellite, the Atacama Cosmology Telescope, and South Pole Telescope. We also consider low redshift observations in the form of baryon acoustic oscillation (BAO) data from the SDSS-IV eBOSS survey and supernovae (SN) distance moduli measurements from the Pantheon-Plus catalog. The marginalized errors are stable against the different minimal extensions of the $\mathrm{\Lambda }\mathrm{CDM}$ model explored in this study. The largest impact on the parameter accuracy is produced by varying the effective number of relativistic degrees of freedom ($N_{\mathrm{eff}}$) or the lensing amplitude ($A_{\mathrm{lens}}$). Nevertheless, the marginalized errors on some derived parameters such as $H_0$ or ${\mathrm{\Omega }}_{\mathrm{m}}$ can be up to 2 orders of magnitude larger than in the canonical $\mathrm{\Lambda }\mathrm{CDM}$ scenario when considering only CMB data. In these cases, low redshift measurements are crucial for restoring the stability of the marginalized cosmological errors computed here. Overall, our results underscore remarkable stability in the mean values and precision of the main cosmological parameters once both high and low redshift probes are fully accounted for. The marginalized values can be used in numerical analyses due to their robustness and slightly larger errors, providing a more realistic and conservative approach.

We derive the differential age signal valid for cosmic chronometers (passively evolving galaxies) in any space-time that satisfies the following assumptions: (i) The space-time has a metric with Lorentzian signature and the connection is the Levi-Civita connection; (ii) the cosmic chronometers are collectively well approximated as a geodesic and irrotational congruence of timelike worldlines in the space-time; (iii) light travels on null geodesics and caustics on the observer’s past light cone can be ignored; (iv) the space-time is cosmological, meaning that isotropic and positive expansion degrees of freedom dominate over anisotropic and negative expansion degrees of freedom when viewed on sufficiently large scales in the frame of the cosmic chronometers. The main result of the paper is an expression for the differential age signal that is written in terms of line-of-sight averages of the expansion rate along individual null lines, thus providing a kinematic interpretation of the differential age signal applicable to cosmological space-times satisfying (i)–(iv). We explain how this result indicates that the differential age signal is a robust probe of the volume-average expansion rate in very general statistically homogeneous and isotropic space-time scenarios where other probes of the volume-average expansion rate tend to yield biased results. We argue that this unique property of the differential age signal makes it an ideal measurement for constraining the expansion history model independently.