Recent work on calculating string theory landscape statistical predictions for the Higgs boson and sparticle mass spectrum from an assumed power-law soft term distribution yields an expectation for $m_h\simeq 125\mathrm{GeV}$ with sparticles (save light Higgsinos) somewhat beyond the reach of the high-luminosity LHC. A recent examination of the statistics of supersymmetry breaking in IIB string models with stabilized moduli suggests a power law for models based on Kachru-Kallosh-Linde-Trivedi stabilization and uplifting, while models based on the large-volume scenario instead yield an expected logarithmic soft term distribution. We evaluate statistical distributions for the Higgs boson and sparticle masses from the landscape with a log soft term distribution and find the Higgs mass still peaks around $\sim 125\mathrm{GeV}$ with sparticles beyond the LHC reach, albeit with somewhat softer distributions than those arising from a power law.

Fixed target missing-momentum experiments such as LDMX and ${\mathrm{M}}^3$ are powerful probes of light dark matter and other light, weakly coupled particles beyond the Standard Model (SM). Such experiments involve $\sim 10\mathrm{GeV}$ beam particles whose energy and momentum are individually measured before and after passing through a suitably thin target. If new states are radiatively produced in the target, the recoiling beam particle loses a large fraction of its initial momentum, and no SM particles are observed in a downstream veto detector. We explore how such experiments can use kinematic variables and experimental parameters, such as beam energy and polarization, to measure properties of the radiated particles and discriminate between models if a signal is discovered. In particular, the transverse momentum of recoiling particles is shown to be a powerful tool to measure the masses of new radiated states, offering significantly better discriminating ability compared to the recoil energy alone. We further illustrate how variations in beam energy, polarization, and lepton flavor (i.e., electron or muon) can be used to disentangle the possible the Lorentz structure of the new interactions.

Models with gauge symmetry $SU(3{)}_c\otimes SU(3{)}_L\otimes U(1{)}_N$ have different candidates for dark matter, for example, a heavy neutral fermion interacting with standard model particles through different mediators, scalar and vector portals. At the same time, these portals can produce signals in the anomalous magnetic moment of the muon that violate the present bounds on this quantity. Combining the requirement to have a dark matter candidate in the $SU(3{)}_c\otimes SU(3{)}_L\otimes U(1{)}_N$ model with heavy neutral leptons and to explain the anomalous magnetic moment of the muon we set constraints on the highest symmetry breaking scale of the model. These bounds are competitive with the constraints from LHC and set a favored region that can also be tested in future direct detection experiments, such as the LUX-ZEPLIN (LZ) experiment.

Motivated by the recent Xenon1T result, we study a leptophilic flavor-dependent anomaly-free axionlike particle (ALP) and its effects on charged-lepton flavor violation. We present two representative models. The first one considers that the ALP origins from the flavon that generates the charged-lepton masses. The second model assumes a larger flavor symmetry such that more general mixings in the charged-lepton are possible, while maintaining flavor-dependent ALP couplings. We find that a keV ALP explaining the Xenon1T result is still viable for lepton flavor violation and stellar cooling astrophysical limits. On the other hand, if the Xenon1T result is confirmed, future charged-lepton flavor violation measurements can be complementary to probe such a possibility.

A new $U(1)$ “dark” gauge group coupled to the Standard Model (SM) via the kinetic mixing portal provides a dark matter candidate in the form of the Higgs field, $h_d$, responsible for generating the mass of the dark photon, ${\gamma }_d$. We show that the condition $m_{h_d}\le m_{{\gamma }_d}$, together with smallness of the kinetic mixing parameter, $\epsilon$, and/or dark gauge coupling, $g_d$, leads the dark Higgs to be sufficiently metastable to constitute dark matter. We analyze the Universe’s thermal history and show that both freeze-in, $\mathrm{SM}\to \{{\gamma }_d,h_d\}$, and freeze-out, $\{{\gamma }_d,h_d\}\to \mathrm{SM}$, processes can lead to viable dark Higgs dark matter with a sub-GeV mass and a kinetic mixing parameter in the range ${10}^{-13}\lesssim \epsilon \lesssim {10}^{-6}$. Observable signals in astrophysics and cosmology include modifications to primordial elemental abundances, altered energetics of supernovae explosions, dark Higgs decays in the late Universe, and dark matter self-interactions.

We discuss a gauged XY model a $\theta$-term on an arbitrary lattice in $1+1$ dimensions and show that the theory reduces exactly to the 2d Ising model on the dual lattice in the limit of the strong gauge coupling, provided that the topological term is defined via the Villain action. We discuss the phase diagram by comparing the strong and weak gauge coupling limits and perform Monte Carlo simulations at intermediate couplings. We generalize the duality to higher-dimensional Ising models using higher-form U(1) gauge field analogs.

We propose a novel Bayesian method to analytically continue observables to real baryochemical potential ${\mu }_B$ in finite density QCD. Taylor coefficients at ${\mu }_B=0$ and data at imaginary chemical potential ${\mu }_B^I$ are treated on equal footing. We consider two different constructions for the Padé approximants, the classical multipoint Padé approximation and a mixed approximation that is a slight generalization of a recent idea in Padé approximation theory. Approximants with spurious poles are excluded from the analysis. As an application, we perform a joint analysis of the available continuum extrapolated lattice data for both pseudocritical temperature $T_c$ at ${\mu }_B^I$ from the Wuppertal-Budapest Collaboration and Taylor coefficients ${\kappa }_2$ and ${\kappa }_4$ from the HotQCD Collaboration. An apparent convergence of $[p/p]$ and $[p/p+1]$ sequences of rational functions is observed with increasing $p$. We present our extrapolation up to ${\mu }_B\approx 600\mathrm{MeV}$.

Reliably computing the free energy in a gauge theory like QCD is a challenging and resource-demanding endeavor. We explore the possibility to obtain the associated thermodynamic anomaly from two-point functions based on a conjectured relation. This conjecture is triggered by the relation to the Tan contact in condensed matter systems. For this investigation we use state-of-the-art results for the Yang-Mills gluon two-point function from the lattice and the functional renormalization group, as well as novel Dyson-Schwinger results at finite temperature computed in the present work. This allows for a first, qualitative, test of this conjecture. The results from all methods reveal the same nontrivial temperature behavior of the subleading large momentum dependence of the gluon propagator relevant for the conjectured relation. The comparison with the expected behavior for SU(2) Yang-Mills theory is encouraging to further pursue this approach.

We generalize the factorization of Abelian gauge theory amplitudes to next-to-leading power (NLP) in a soft scale expansion, following a recent generalization for Yukawa theory. From an all-order power counting analysis of leading and next-to-leading regions, we infer the factorized structure for both a parametrically small and zero fermion mass. This requires the introduction of new universal jet functions, for nonradiative and single-radiative QED amplitudes, which we compute at one-loop order. We show that our factorization formula reproduces the relevant regions in one- and two-loop scattering amplitudes, appropriately addressing endpoint divergences. It provides a description of virtual collinear modes and accounts for nontrivial hard-collinear interplay present beyond the one-loop level, making this a first step toward a complete all-order factorization framework for gauge-theory amplitudes at NLP.

Leading neutron production in $ep$ collisions at high energies is investigated using the color dipole formalism and taking into account saturation effects. We update the treatment of absorptive effects and estimate the impact of these effects on leading neutron spectra in the kinematical range that will be probed by the Electron Ion Collider (EIC) and by the Large Hadron electron Collider (LHeC). We demonstrate that Feynman scaling, associated with saturation, is not violated by the inclusion of absorptive effects. Moreover, our results indicate that the leading neutron spectrum is strongly suppressed at small photon virtualities. These results suggest that absorptive effects cannot be disregarded in future measurements of the $\gamma \pi$ cross section to be extracted from data on leading neutron production.

We propose a model for combining the Standard Model (SM) with gravity. It relies on a nonminimal coupling of the Higgs field to the Ricci scalar and on the Palatini formulation of gravity. Without introducing any new degrees of freedom in addition to those of the SM and the graviton, this scenario achieves two goals. First, it generates the electroweak symmetry breaking by a nonperturbative gravitational effect. In this way, it does not only address the hierarchy problem but opens up the possibility to calculate the Higgs mass. Second, the model incorporates inflation at energies below the onset of strong-coupling of the theory. Provided that corrections due to new physics above the scale of inflation are not unnaturally large, we can relate inflationary parameters to data from collider experiments.

We study ${\eta }_{\mathrm{c}}$ production at center-of-mass energies $\sqrt{s}$ from 4.18 to 4.60 GeV in $e^{+}{e}^{-}$ annihilation data collected with the BESIII detector operating at the BEPCII storage ring, corresponding to $7.3{\mathrm{fb}}^{-1}$ of integrated luminosity. We measure the cross sections of the three different exclusive reactions $e^{+}{e}^{-}\to {\eta }_{\mathrm{c}}{\pi }^{+}{\pi }^{-}{\pi }^0$, $e^{+}{e}^{-}\to {\eta }_{\mathrm{c}}{\pi }^{+}{\pi }^{-}$, and $e^{+}{e}^{-}\to {\eta }_{\mathrm{c}}{\pi }^0\gamma$. We find significant ${\eta }_{\mathrm{c}}$ production in $e^{+}{e}^{-}\to {\eta }_{\mathrm{c}}{\pi }^{+}{\pi }^{-}{\pi }^0$ at $\sqrt{s}$ of 4.23 GeV and 4.26 GeV and observe a significant energy-dependent Born cross section that we measure to be consistent with the production via the intermediate $Y(4260)$ resonance. In addition, we perform a search for a charmoniumlike $Z_{\mathrm{c}}$ state close to the $D\overline{D}$ threshold that decays to ${\eta }_{\mathrm{c}}\pi$, involving ground state charmonium, and observe no signal. Corresponding upper limits on the cross section of ${\eta }_{\mathrm{c}}$ and $Z_{\mathrm{c}}$ production are provided, where the yields are not found to be significant.

Recent cosmic microwave background observations favor low-energy-scale inflationary models in a closed universe. However, the onset of inflation in such models for a closed universe is known to be severely problematic. In particular, such a universe recollapses within a few Planck seconds and encounters a big crunch singularity when initial conditions are given in the Planck regime. We show that this problem of the onset of inflation in low-energy-scale inflationary models can be successfully overcome in a quantum-gravitational framework where the big bang/big crunch singularities are resolved and a nonsingular cyclic evolution exists prior to inflation. As an example, we consider a model in loop quantum cosmology and demonstrate that the successful onset of low-energy-scale inflation in a closed universe is possible for the Starobinsky inflationary model starting from a variety of initial conditions where it is impossible in the classical theory. For comparison, we also investigate the onset of inflation in the ${\varphi }^2$ inflationary model under highly unfavorable conditions and find similar results. Our numerical investigation including the phase-space analysis shows that the preinflationary phase with quantum gravity effects is composed of nonidentical cycles of bounces and recollapses resulting in a hysteresis-like phenomenon, which plays an important role in creating suitable conditions for inflation to occur after some number of nonsingular cycles. Our analysis shows that the tension in the classical theory amounting to the unsuitability of closed Friedmann-Lemaître-Robertson-Walker universes with respect to the onset of low-energy-scale inflation can be successfully resolved in loop quantum cosmology.

It is expected that all astrophysical black holes in equilibrium are well described by the Kerr solution. Moreover, any black hole far away from equilibrium, such as one initially formed in a compact binary merger or by the collapse of a massive star, will eventually reach a final equilibrium Kerr state. At sufficiently late times in this process of reaching equilibrium, we expect that the black hole is modeled as a perturbation around the final state. The emitted gravitational waves will then be damped sinusoids with frequencies and damping times given by the quasinormal mode spectrum of the final Kerr black hole. An observational test of this scenario, often referred to as black hole spectroscopy, is one of the major goals of gravitational wave astronomy. It was recently suggested that the quasinormal mode description including the higher overtones might hold even right after the remnant black hole is first formed. At these times, the black hole is expected to be highly dynamical and nonlinear effects are likely to be important. In this paper we investigate this remarkable scenario in terms of the horizon dynamics. Working with high accuracy simulations of a simple configuration, namely the head-on collision of two nonspinning black holes with unequal masses, we study the dynamics of the final common horizon in terms of its shear and its multipole moments. We show that they are indeed well described by a superposition of ringdown modes as long as a sufficiently large number of higher overtones are included. This description holds even for the highly dynamical final black hole shortly after its formation. We discuss the implications and caveats of this result for black hole spectroscopy and for our understanding of the approach to equilibrium.

The propagation of high-frequency gravitational waves can be analyzed using the geometrical optics approximation. In the case of large but finite frequencies, the geometrical optics approximation is no longer accurate and polarization-dependent corrections at first order in wavelength modify the propagation of gravitational waves, via a spin-orbit coupling mechanism. We present a covariant derivation from first principles of effective ray equations describing the propagation of polarized gravitational waves, up to first-order terms in wavelength, on arbitrary spacetime backgrounds. The effective ray equations describe a gravitational spin Hall effect for gravitational waves and are of the same form as those describing the gravitational spin Hall effect of light, derived from Maxwell’s equations.

We present interesting aspects of neutron stars (NSs) from the standpoint of a modified theory of gravity called Hořava-Lifshitz (HL) gravity. A deviation from general relativity (GR) in HL gravity can change typical features of the NS structure. In this study, we investigate the NS structure by deriving the Tolman-Oppenheimer-Volkoff equation in HL gravity. We find that a NS in HL gravity with a larger radius and heavier mass than a NS in GR remains stable without collapsing into a black hole.

We investigate how pure-state Einstein-Podolsky-Rosen correlations in the internal degrees of freedom of massive particles are affected by a curved spacetime background described by extended theories of gravity. We consider models for which the corrections to the Einstein-Hilbert action are quadratic in the curvature invariants and we focus on the weak-field limit. We quantify nonlocal quantum correlations by means of the violation of the Clauser-Horne-Shimony-Holt inequality, and show how a curved background suppresses the violation by a leading term due to general relativity and a further contribution due to the corrections to Einstein gravity. Our results can be generalized to massless particles such as photon pairs and can thus be suitably exploited to devise precise experimental tests of extended models of gravity.

We consider monochromatic and isotropic photon emission from circular equatorial Kerr orbiters. We derive analytic expressions for the photon escape probability and the redshift-dependent total flux collected on the celestial sphere as a function of emission radius and black hole parameters. These calculations crucially involve the critical curve delineating the region of photon escape from that of photon capture in each emitter’s sky. This curve generalizes to finite orbital radius the usual Kerr critical curve and displays interesting features in the limit of high spin, which we investigate by developing a perturbative expansion about extremality. Although the innermost stable circular orbit appears to approach the event horizon for very rapidly spinning black holes, we find in this regime that the photon escape probability tends to $5/12+1/(\sqrt{5}\pi )\arctan \sqrt{5/3}\approx 54.65\%$. We also obtain a simple formula for the flux distribution received on the celestial sphere, which is nonzero. This confirms that the near-horizon geometry of a high-spin black hole is in principle observable. These results require us to introduce a novel type of near-horizon double-scaling limit. We explain the dip observed in the total flux at infinity as an imprint of the black hole: the black hole “bite.”

The concept of turnaround surface in an accelerating universe is generalized to arbitrarily large deviations from spherical symmetry, to close the gap between the idealized theoretical literature and the real world observed by astronomers. As an analytical application, the characterization of turnaround surface is applied to small deviations from spherical symmetry, recovering a previous result while extending it to scalar-tensor gravity.

The Penrose process of an extremal Banãdos-Teitelboim-Zanelli (BTZ) black hole is studied. Due to the existence of negative cosmological constant, only massless particles could escape to infinity. Hence we analyze the Penrose process by one massless particle collides with another massive particle. Calculations of the maximum energy extraction efficiency of this process is carried out for both spinless and spinning particles. Our results show that the spinning particle have a higher energy extraction efficiency than the spinless particle. Moreover, our calculation also indicates that the maximum energy extraction efficiency is independent of the value of the cosmological constant of BTZ black holes.