We study the implications of finite naturalness in Pati-Salam models where $\mathrm{SU}(3{)}_C$ is embedded in SU(4). For the minimal realization at low scale of quark-lepton unification, which employs the inverse seesaw for neutrino masses, we find that radiative corrections to the Higgs boson mass are at least $\delta m_h^2/m_h^2\sim \mathcal{O}({10}^4)$. The one-loop contributions to the Higgs mass are suppressed by four powers of the hypercharge gauge coupling. We find that for the vector leptoquarks the naively leading part of the two-loop corrections cancel. We assume the Dirac Yukawa couplings for neutrinos are equal to the up-type quark Yukawa couplings as predicted in the minimal theory for quark-lepton unification. Despite these findings, the two-loop corrections still dominate the finite naturalness bound. We mention a way to relax the lower bound on the vector leptoquark mass and have $\delta m_h^2/m_h^2\sim \mathcal{O}({10}^2)$.

We use anti-de Sitter/quantum chromodynamics based holographic light-front wavefunction (LFWF) for vector meson, in conjunction with the dipole model to investigate the cross sections data for the diffractive and exclusive $\mathrm{J}/\psi$ and $\psi (2S)$ production. We confront the experimental data using a new explicit form of the holographic LFWF, where the longitudinal confinement dynamics in the light-front Schrödinger equation is captured by the ’t Hooft equation of ($1+1$)-dim, in large $N_c$ approximation, in addition to the transverse confinement dynamics governed by the confining mass scale parameter $\kappa$ in vector mesons. We obtain the LFWF parameters from fitting to the exclusive $\mathrm{J}/\psi$ electroproduction data from the electron-proton collision at the Hadron Electron Ring Accelerator collider for $m_c=1.27\mathrm{GeV}$. Our results suggest that the dipole model together with holographic meson LFWFs with longitudinal confinement is able to give a successful description for differential scattering cross section for exclusive $\mathrm{J}/\psi$ electroproduction for H1 and ZEUS data. We also predict the rapidity distributions of differential scattering cross section and total photoproduction of $\mathrm{J}/\psi$ and $\psi (2S)$ states in proton-proton ultraperipheral collisions (UPCs) at center of mass energy $\sqrt{s}=7,13\mathrm{TeV}$. Using the minimum set of parameters, our predictions for the UPCs are in good agreement with the recent experimental observations of UPCs at ALICE and LHCb Collaborations.

Recent advances in $b$, $c$, and $s$ quark tagging coupled with novel statistical analysis techniques will allow future high energy and high statistics electron-positron colliders, such as the FCC-ee, to place phenomenologically relevant bounds on flavor violating Higgs and $Z$ decays to quarks. We assess the FCC-ee reach for $Z/h\to bs,cu$ decays as a function of jet tagging performance. We also update the standard model (SM) predictions for the corresponding branching ratios, as well as the indirect constraints on the flavor violating Higgs and $Z$ couplings to quarks. Using the type III two Higgs doublet model as an example of beyond the standard model physics, we show that the searches for $h\to bs,cu$ decays at FCC-ee can probe new parameter space not excluded by indirect searches. We also reinterpret the FCC-ee reach for $Z\to bs,cu$ in terms of the constraints on models with vectorlike quarks.

We show that there is a remarkable phase in quantum gravity where gravitational scattering amplitudes mediated by virtual gravitons can be calculated explicitly in effective field theory, when the impact parameter $b$ satisfies $L_{\mathrm{Pl}}\ll b\lesssim R_S$, with $R_S$ being the Schwarzschild radius. This phase captures collisions with energies satisfying $\sqrt{s}\gg \gamma M_{\mathrm{Pl}}$ (with $\gamma \sim M_{\mathrm{Pl}}/M_{\mathrm{BH}}$) near the horizon. We call this the black hole eikonal phase, in contrast to its flat space analog where collisions are trans-Planckian. Hawking’s geometric optics approximation neglects gravitational interactions near the horizon, and results in thermal occupation numbers in the Bogoliubov coefficients. We show that these interactions are mediated by graviton exchange in $2\to 2$ scattering near the horizon, and explicitly calculate the $S$-matrix nonperturbatively in $M_{\mathrm{Pl}}/M_{\mathrm{BH}}$. This involves a resummation of infinitely many ladder diagrams near the horizon, all mediated by virtual soft gravitons. The $S$-matrix turns out to be a pure phase upon this resummation and is agnostic of Planckian physics and any specific ultraviolet completion. In contrast to the flat-space eikonal limit, the black hole eikonal phase captures collisions of extremely low energy near the horizon.

$(1+1)$-dimensional locally de Sitter–Friedmann-Robertson-Walker cosmologies with compact spatial sections allow cosh, sinh, and exponential evolution laws, each with a freely specifiable spatial circumference parameter, and the value of this parameter has an invariant geometric meaning for the cosh and sinh evolution laws. We identify geometrically preferred states for a quantized massive scalar field on these cosmologies, some singled out by adiabatic criteria in the distant past, with an ambiguity remaining due to a massive zero mode, and others induced from the Euclidean vacuum on standard ($1+1$)-dimensional de Sitter space by a quotient construction. We show that a comoving quantum observer, modelled as an Unruh-DeWitt detector, can distinguish these states from the Euclidean vacuum on standard de Sitter space. Numerical plots are given in selected parameter regimes. We also evaluate the field’s stress-energy tensor expectation value for those states that are induced from the Euclidean vacuum by a quotient construction.

A variational principle for gauge theories of gravity is presented, which maintains manifest covariance under the symmetries to which the action is invariant, throughout the calculation of the equations of motion and conservation laws. This is performed by deriving explicit manifestly covariant expressions for the Euler-Lagrange variational derivatives and Noether’s theorems for a generic action of the form typically assumed in gauge theories of gravity. The approach is illustrated by application to two scale-invariant gravitational gauge theories, namely Weyl gauge theory (WGT) and the recently proposed ‘extended’ Weyl gauge theory (eWGT), where the latter may be considered as a novel gauging of the conformal group; the method can also be straightforwardly applied to other theories with smaller or larger symmetry groups. In addition, the approach enables one easily to establish the relationship between manifestly covariant forms of variational derivatives obtained when one or more of the gauge field strengths is set to zero either before or after the variation is performed. This is illustrated explicitly for both WGT and eWGT in the case where the translational gauge field strength (or torsion) is set to zero before and after performing the variation, respectively.

In this work we analyze the motion of charged particles in the background of the Kiselev geometry, which is considered here as an exact solution in the context of power-Maxwell electrodynamics. As it is well known, one can use either an electric ansatz or a magnetic one for the nonlinear electromagnetic field. We study the motion of an electrically charged particle for an electrically charged black hole and also for a magnetically charged black hole. In the second case the motion is restricted to Poincaré cones of various angles, as expected.

In early dark energy (EDE) resolution of Hubble tension, the spectral index $n_s$ of primordial scalar perturbation follows a scaling relation $\delta n_s\simeq 0.4\frac{\delta H_0}{H_0}$, where $H_0$ is the Hubble constant. However, this $n_s-H_0$ relation was obtained based on the data sets that include Planck cosmic microwave background (CMB) data. In this paper, we investigate this scaling relation with Planck-independent CMB data, i.e., ACT and SPT-3G combined with $\mathrm{WMAP}(+\mathrm{BAO}+\mathrm{Pantheon})$, respectively. Our results show that the $\mathrm{WMAP}+\mathrm{SPT}\text{−}3\mathrm{G}$ data set also follows this scaling relation, while the $\mathrm{WMAP}+\mathrm{ACT}$ data set seems to favor smaller $n_s$, which is related to the fact that the critical redshift $z_c$, at which EDE is excited, favored by the $\mathrm{WMAP}+\mathrm{ACT}$ data set is lower and closer to the recombination time.

The fluid forces associated with primordial magnetic fields (PMFs) generate small-scale fluctuations in the primordial density field, which add to the $\mathrm{\Lambda }\mathrm{CDM}$ linear matter power spectrum on small scales. These enhanced small-scale fluctuations lead to earlier formation of galactic halos and stars and thus affect cosmic reionization. We study the consequences of these effects on 21-cm observables using the seminumerical code 21cmFAST v3.1.3. We find the excess small-scale structure generates strong stellar radiation backgrounds in the early Universe, resulting in altered 21-cm global signals and power spectra commensurate with earlier reionization. We restrict the allowed PMF models using the CMB optical depth to reionization. Lastly, we probe parameter degeneracies and forecast experimental sensitivities with an information matrix analysis subject to the cosmic microwave background (CMB) optical depth bound. Our forecasts show that interferometers like HERA are sensitive to PMFs of order $\sim \mathrm{pG}$, nearly an order of magnitude stronger than existing 21-cm observatories and future standalone CMB experiments.

Using analytical tools from linear response theory, we systematically assess the accuracy of several microscopic derivations of Israel-Stewart hydrodynamics near local equilibrium. This allows us to “rank” the different approaches in decreasing order of accuracy as follows: inverse Reynolds dominance (IReD), Denicol-Niemi-Molnár-Rischke (DNMR), second-order gradient expansion, and 14-moment approximation. We find that IReD theory is far superior to Navier-Stokes, being very accurate both in the asymptotic regime (i.e., for slow processes) and in the transient regime (i.e., on timescales comparable to the relaxation time). Also, the high accuracy of DNMR is confirmed, but neglecting second-order terms in the Knudsen number, which would render the equations parabolic, introduces serious systematic errors. Finally, in most cases, the second-order gradient expansion (also known as nonresummed Baier-Romatschke-Son-Starinets-Stephanov) is found to be more inaccurate than Navier-Stokes in the transient regime. Overall, this analysis shows that Israel-Stewart hydrodynamics is falsifiable, and the relaxation time is observable, shedding new light on the debate on the viability of transient hydrodynamics as a well-defined physical theory distinguished from Navier-Stokes.

Inspired by self-adjoint extensions of the electric field operator in the Hamiltonian formalism, we extend the Wilsonian framework of Abelian lattice gauge theory by introducing a modified action parametrized by an angle $\alpha$, where the ordinary Wilson theory corresponds to $\alpha =0$. Choosing instead $\alpha =\pi$ (the “staggered” case) gives the only other theory in the family which preserves all symmetries of the original model at the microscopic level. We study the case of $3D$ $U(1)$ pure gauge theory, simulating the staggered case of this model numerically in its dual formulation. We find evidence of a continuum limit with a spontaneously broken ${\mathbb{Z}}_2$ single-site translational symmetry, in contrast to the ordinary theory. Moreover, the confining string fractionalizes into multiple strands which separate spatial regions in distinct ground states of the broken symmetry.

The effect of the temperature evolution of quark-gluon plasma (QGP) on its thermal conductivity and elliptic flow is investigated here in the presence of a time-varying magnetic field. Thermal conductivity plays a vital role in the cooling rate of the medium or its temperature evolution. The magnetic field produced during the early stages of (noncentral) heavy-ion collisions decays with time, where electrical conductivity plays a significant role. As the medium expands, the electrical and thermal properties change, reflecting the effect in various observables. In this study, we have calculated the thermal conductivity of the QGP medium, incorporating the effects of temperature and magnetic field evolution. We discovered that conductivity significantly depends on the cooling rate, and its value increases due to temperature evolution. Furthermore, the influence of these evolutions on the elliptic flow coefficient is measured, and elliptic flow decreases due to the evolution. We also extend our study for the case of Gubser flow, where, along with the longitudinal Bjorken expansion, the radially transverse expansion is also present.

In this work, we take the $X(3872)$ as the hidden-charm tetraquark state with both isospin $I=0$ and $I=1$ components, then investigate the strong decays $X(3872)\to J/\psi {\pi }^{+}{\pi }^{-}$, $J/\psi \omega$, ${\chi }_{c1}{\pi }^0$, $D^{*0}{\overline{D}}^0$, and $D^0{\overline{D}}^0{\pi }^0$ with the QCD sum rules. We take account of all the Feynman diagrams, and acquire four QCD sum rules based on rigorous quark-hadron duality. We obtain the total decay width about 1 MeV, which is in excellent agreement with the experiment data ${\mathrm{\Gamma }}_X=1.19\pm 0.21\mathrm{MeV}$ from the PDG, it is the first time to reproduce the tiny width of the $X(3872)$ via the QCD sum rules, which supports assigning the $X(3872)$ as the hidden-charm tetraquark state with the $J^{PC}=1^{++}$.

The internal structure of all lowest-lying pseudoscalar mesons with heavy-light quark content is studied in detail using an algebraic model that has been applied recently, and successfully, to the same physical observables of pseudoscalar and vector mesons with hidden-flavor quark content, from light to heavy quark sectors. The algebraic model consists on constructing simple and evidence-based Ansätze of the meson’s Bethe-Salpeter amplitude (BSA) and quark’s propagator in such a way that the Bethe-Salpeter wave function (BSWF) can then be readily computed algebraically. Its subsequent projection onto the light front yields the light front wave function (LFWF) whose form allows us a simple access to the valence-quark parton distribution amplitude (PDA) by integrating over the transverse momentum squared. We exploit our current knowledge of the PDAs of lowest-lying pseudoscalar heavy-light mesons to compute their generalized parton distributions (GPDs) through the overlap representation of LFWFs. From these three dimensional knowledge, different limits/projections lead us to deduce the related parton distribution functions (PDFs), electromagnetic form factors (EFFs), and impact parameter space GPDs (IPS-GPDs). When possible, we make explicit comparisons with available experimental results and earlier theoretical predictions.

We study the exclusive near threshold photoproduction of heavy quarkonium in the framework of the generalized parton distribution (GPD) factorization, taking the $J/\psi$ production as an example. Because of the threshold kinematics, the Compton-like amplitudes are related to gluon GPDs at large skewness $\xi$, distinct from the common kinematics in asymptotic high energy where the skewness is typically small. We discuss the nature of large-$\xi$ expansion of these amplitudes in terms of the moments of gluon GPDs in the large-$\xi$ limit. Based on that, we propose several ways to extract the first few moments of the gluon GPDs from these amplitudes, with the leading ones corresponding to the gluonic gravitational or energy-momentum tensor form factors (GFFs). We apply these methods to analyze the recent near threshold $J/\psi$ production measurements by the $J/\psi$ 007 experiment and GlueX Collaboration and find that the $\xi$ scaling of the measured differential cross sections is consistent with the asymptotic behavior. However, the current data are not accurate enough yet for a complete determination of the gluonic GFFs, and therefore we consider some prospects for better extractions in the future.

We present a scalable technique for the simulation of collider events with multijet final states, based on an improved parton-level event file format and scalable $\mathrm{I}/\mathrm{O}$. The method is implemented for both leading- and next-to-leading-order QCD calculations. We perform a comprehensive analysis of the computing performance and validate our new framework using Higgs-boson plus multijet production with up to seven jets. We make the resulting code base available for public use.

Baryon asymmetry of the Universe offers one of the strongest hints for physics beyond the Standard Model (BSM). Remarkably, in the general two Higgs doublet model ($g2\mathrm{HDM}$) that possesses a second set of Yukawa matrices, one can have electroweak baryogenesis (EWBG) while the electron electric dipole moment (eEDM) is evaded by a natural flavor tuning that echoes the Standard Model (SM). We show that eEDM may first emerge around ${10}^{-30}e\mathrm{cm}$ or so, followed by neutron EDM (nEDM) down to ${10}^{-27}e\mathrm{cm}$. We illustrate a cancellation mechanism for nEDM itself, which in turn can be probed when a facility capable of pushing down to ${10}^{-28}e\mathrm{cm}$ becomes available.

We investigate semileptonic form factors of a $D_{(s)}$ meson from a modified soft-wall 4-flavor holographic model. The model successfully reproduces the masses and decay constants of various mesons, including $\rho$, $K^{*}$, $D^{*}$, $D_s^{*}$, $a_1$, $K_1$, $f_1$, $D_1$, $D_{s1}$, $\pi$, $K$, $\eta$, $D$, and $D_s$. Moreover, we study the semileptonic decay processes $D^{+}\to (\pi ,K,\eta )l^{+}{\nu }_l$ and $D_s^{+}\to (K,\eta )l^{+}{\nu }_l$, associated with the vector meson exchange, as well as $D_{(s)}^{+}\to K{l}^{+}{\nu }_l$, associated with the vector and axial vector meson exchange. The form factors $f_{+}(q^2)$ for $D\to \pi$ and $D_{(s)}\to K$ decays agree excellently with experimental and lattice data, outperforming other theoretical approaches. The $f_{+}(q^2)$ form factor for $D^{+}\to \eta$ is compatible with experimental data, while a slight discrepancy is observed for $D_s^{+}\to \eta$ at large $q^2$. Additionally, we predict the vector form factors $V(q^2)$ and $A_1(q^2)$ for $D\to K$ and $D_s\to K$ decays, respectively. The results agree well with other approaches and lattice data at maximum recoil ($q^2=0$).

We use the gravitational path integral (GPI) to compute the fluctuations of the Hawking radiation entropy around the Page curve in a two-dimensional model introduced by Penington et al. Before the Page time, we find that $\delta S=e^{-S}/\sqrt{2}$, where $S$ is the black hole entropy. This result agrees with the Haar-averaged entropy fluctuations in a bipartite system. After the Page time, we find that $\delta S\sim e^{-S}$, up to a prefactor that depends logarithmically on the width of the microcanonical energy window. This is not symmetric under exchange of subsystem sizes and so does not agree with the Haar average for a subsystem of fixed Hilbert space dimension. The discrepancy can be attributed to the fact that the black hole Hilbert space dimension is not fixed by the state preparation: even in a microcanonical ensemble with a top-hat smearing function, the GPI yields an additive fluctuation in the number of black hole states. This result, and the fact that the Page curve computed by the GPI is smooth, all point towards an ensemble interpretation of the GPI.