We perform a model-independent global fit to all germane and updated $b\to s\ell \ell$ ($\ell =e$, $\mu$) data assuming new physics couplings to be complex. Under the approximation that new physics universally affects muon and electron sectors and that either one or two related operators contribute at a time, we identify scenarios which provide a good fit to the data. It turns out that the favored scenarios remain the same as obtained for the real fit. Further, the magnitude of complex couplings can be as large as that of their real counterparts and these are reflected in the predictions of the direct $CP$ asymmetry, $A_{CP}$, in $B\to (K,K^{*}){\mu }^{+}{\mu }^{-}$ along with a number of angular $CP$ asymmetries, $A_i$, in $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$ decay. The sensitivities of these observables to various solutions are different in the low and high-$q^2$ bins. We also determine observables which can serve as unique identifier for a particular new physics solution. Moreover, we examine correlations between $A_{CP}$ and several $A_i$ observables. A precise measurement of $A_{CP}$ and $A_i$ observables can not only confirm the existence of additional weak phases but can also enable unique determination of Lorentz structure of possible new physics in $b\to s{\mu }^{+}{\mu }^{-}$ transition.

The $DK$ interaction in isospin zero is known to be attractive to such an extent that a bound state can be generated, which can be associated with the mysterious $D_{s0}^{*}(2317)$. In this work, we calculate the $DK$ femtoscopic correlation function in the coupled-channel framework for different source sizes that can directly probe the strongly attractive $DK$ interaction, which is otherwise inaccessible due to the unstable nature of $D$ and $K$ mesons, and therefore can help elucidate the nature of $D_{s0}^{*}(2317)$. We further generalize the study of source size dependence to various interactions, ranging from repulsive, weakly attractive, moderately attractive, and strongly attractive, in a square-well model. We hope that our study can motivate future experimental measurements of the $DK$ correlation function and other interactions relevant to the understanding of the nature of the many exotic hadrons discovered so far.

We use low-redshift background cosmology data to place quantitative constraints on three separate modified gravity models, each of which aims to explain the low-redshift acceleration through a different physical mechanism. The Lifshitz cosmology is effectively a parametric extension of the canonical $\mathrm{\Lambda }\mathrm{CDM}$ model, where a time-dependent cosmological constant originates from vacuum energy. The infinite statistics model is also a parametric extension of $\mathrm{\Lambda }\mathrm{CDM}$, where the dark energy is dynamic and originates from the curvature of a dual space-time. We show that the data restrict the additional parameters in these models to be consistent with their $\mathrm{\Lambda }\mathrm{CDM}$ values, and in particular that the data imply that the theoretically predicted value for a dimensionless coupling parameter in the Lifshitz model is ruled out at more than 6 standard deviations. In the Regge-Teitelboim model, gravity is described by embedding the usual space-time manifold in a fixed higher-dimensional background, and there is no parametric $\mathrm{\Lambda }\mathrm{CDM}$ limit. We study several separate realizations of the model, respectively introduced by Davidson, by Fabi et al., and by Stern and Xu, and show that the first two are ruled out by the low-redshift data we use, while the latter is consistent with these data but requires a nonstandard value of the matter density. Overall, our analysis highlights the tight constraints imposed by current data on the allowed low-redshift deviations from the standard $\mathrm{\Lambda }\mathrm{CDM}$ background evolution.

We revisit standard arguments for hyperscaling of the spectrum when a nonzero fermion mass is introduced to a gauge-fermion theory which is conformal in the infrared limit. With some general assumptions, we argue that the induced confinement scale will be significantly enhanced near the edge of the conformal to confining transition. This enhancement can allow for the fermion mass to be arbitrarily small compared to the confinement scale. This scale separation may allow for apparent spontaneous breaking of chiral symmetry within the conformal window, which may be of interest for construction of dilaton effective field theories in this regime.

A two-Higgs doublet model can predict the observed muon $g-2$ for an appropriately light pseudoscalar that now faces tight constraints. However, it was shown recently in the companion paper [N. Chakrabarty, Muon $g-2$ in a type-X 2HDM assisted by inert scalars: A test at the LHC, preceding paper, arXiv:2112.13126.] that augmenting the two-Higgs doublet model by an additional inert doublet can lead to an explanation to the muon $g-2$ anomaly for a much heavier pseudoscalar. In this study, we probe such a framework at the proposed International Linear Collider using beam polarization for $\sqrt{s}=1\mathrm{TeV}$. Using multivariate techniques, we analyze the signals $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}+$ missing transverse energy and $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}+$ missing transverse energy in the lepton- and muon-specific versions of the framework, respectively. Our analysis reveals that the $e^{+}{e}^{-}$ machine operating at a $3000{\mathrm{fb}}^{-1}$ luminosity predicts a $5\sigma$ discovery of a pseudoscalar as heavy as 400 GeV. Comparing with the companion paper, it is concluded that the International Linear Collider is a much more potent machine than the LHC in this regard.

A scenario augmenting the well-known type-X two-Higgs doublet model with an additional inert doublet is proposed. The type-X two-Higgs doublet model is known to offer a solution to the muon $g-2$ anomaly for a light pseudoscalar. We show that the proposed framework can accommodate a heavier pseudoscalar on account of two-loop Barr-Zee contributions to muon $g-2$ stemming from the inert doublet. We subsequently explore an interesting ${\tau }^{+}{\tau }^{-}+$ missing transverse energy signal that can be used to probe the present scenario at the 14 TeV LHC.

We conduct numerical simulations of a model of four-dimensional quantum gravity in which the path integral over continuum Euclidean metrics is approximated by a sum over combinatorial triangulations. At fixed volume, the model contains a discrete Einstein-Hilbert term with coupling $\kappa$ and a local measure term with coupling $\beta$ that weights triangulations according to the number of simplices sharing each vertex. We map out the phase diagram in this two-dimensional parameter space and compute a variety of observables that yield information on the nature of any continuum limit. Our results are consistent with a line of first-order phase transitions with a latent heat that decreases as $\kappa \to \infty$. We find a Hausdorff dimension along the critical line that approaches $D_H=4$ for large $\kappa$ and a spectral dimension consistent with $D_s=\frac{3}{2}$ at short distances. These results are broadly in agreement with earlier works on Euclidean dynamical triangulation models which utilize degenerate triangulations and/or different measure terms and indicate that such models exhibit a degree of universality.

The mass spectra of neutral mesons $K_0,{\pi }_0,\eta ,{\eta }^{\prime }$ on the temperature-quark chemical potential ($T\text{−}\mu$) plane under a constant magnetic field is investigated in the $SU(3)$ Nambu-Jona-Lasinio model. As a Goldstone boson of chiral symmetry breaking, the mass of $K_0$ meson generally increases with temperature and/or quark chemical potential, and we observe two kinds of mass jumps of the $K_0$ meson in medium, one of which is induced by the mass jump of constituent quarks and the other by the magnetic field. Due to the breaking of isospin symmetry between $u$ and $d$ quarks in the presence of magnetic fields, a flavorless neutral meson mixing involving the ${\pi }_0-\eta -{\eta }^{\prime }$ mesons occurs (in the isospin symmetric case the mixing involves only $\eta -{\eta }^{\prime }$) and a rich structure is found in the mass spectra of these mesons. For instance, the ${\pi }_0$ mass is influenced by the strange quark. A change in the slope of the $\mu$ dependency of the ${\pi }_0$ mass at high $\mu$ and vanishing T can be associated with the crossing of the threshold of two times of strange quark mass. In the finite T case, this behavior is changed into the appearance of a critical chemical potential at which a jump over the threshold of $2m_s$ occurs. The mass ordering of ${\pi }_0,\eta ,{\eta }^{\prime }$ mesons varies in medium, due to their mass jumps, which are induced by the mass jump of constituent quarks or the magnetic field.

We present the first effective-one-body model for generic-spins quasicircular black-hole–neutron-star (BHNS) inspiral-merger-ringdown gravitational waveforms (GWs). Our model is based on a new numerical-relativity (NR) informed expression of the BH remnant and its ringdown. It reproduces the NR $(\ell ,m)=(2,2)$ waveform with typical phase agreement of $\lesssim 0.5\mathrm{rad}$ ($\lesssim 1\mathrm{rad}$) to merger (ringdown). The maximum (minimum) mismatch between the (2, 2) and the NR data is 4% (0.6%). Higher modes (HMs) (2, 1), (3, 2), (3, 3), (4, 4), and (5, 5) are included, and their mismatch with the available NR waveforms are up to (down to) a 60% (1%) depending on the inclination. Phase comparison with a 16 orbit precessing simulation shows differences within the NR uncertainties. We demonstrate the applicability of the model in GW parameter estimation by performing the first BHNS Bayesian analysis with HMs (and nonprecessing spins) of the event GW190814, together with new (2, 2)-mode analysis of GW200105 and GW200115. For the GW190814 study, the inclusion of HMs gives tighter parameter posteriors. The Bayes factors of our analyses on this event show decisive evidence for the presence of HMs, but no clear preference for a BHNS or a binary black hole source. Similarly, we confirm GW200105 and GW200115 show no evidence for tidal effects.

We compute bounds and forecasts on screened modified gravity theories, specializing to the chameleon model in Casimir force experiments. In particular, we investigate the classical interaction between a plate and sphere subject to a screened interaction of the chameleon type. We compare numerical simulations of the field profile and the classical pressure exerted on the sphere to analytical approximations for these nonlinear field theories. In particular, we focus on the proximity force approximation (PFA) and show that, within the range of sphere sizes $R$ and plate-sphere distance $D$ simulated numerically, the PFA does not reproduce the numerical results. This differs from the case of linear field theories such as Newtonian gravity and a Yukawa model where the PFA coincides with the exact results. We show that, for chameleon theories, the screening factor approximation, whereby the sphere is modeled as a screened sphere embedded in the external field due to the plates, fares better and can be used in the regime $D\gtrsim R$ to extract constraints and forecasts from existing and forthcoming data. In particular, we forecast that future Casimir experiments would corroborate the closing of the parameter space for the simplest of chameleon models at the dark energy scale.

We consider polar perturbations of static Ellis-Bronnikov wormholes and derive the coupled set of perturbation equations for the gravitational and the scalar field. For massless wormholes the perturbations decouple, and we obtain two identical master equations for the scalar and gravitational modes, which moreover agree with the master equation for the axial modes. Consequently there is isospectrality with threefold degenerate modes. For a finite mass of the background wormhole solutions, the equations are coupled. We then obtain two distinct branches of polar quasinormal modes for a given multipole number $l$, associated with the presence of the two types of fields. We calculate the quasinormal mode frequencies and decay rates for the branches with $l=2$, 3 and 4. For a given $l$ the real frequencies of the two branches get the closer, the higher the multipole number gets.

A cosmological model with a time-varying mass of electrons seems a promising solution for the so-called Hubble tension. We examine the big bang nucleosynthesis (BBN) constraints on the time-varying electron mass model because a larger electron mass gives rise to the smaller weak interaction rate for the proton and neutron conversion, which could affect the light element abundance. Additionally, different inferred cosmological parameters, primarily baryon asymmetry, keeping the cosmic microwave background power spectrum unchanged could affect the abundance of light element. We find that the resultant proton-to-neutron ratio is not so much sensitive with respect to the electron mass because the change of weak interaction rate becomes important after the cosmic temperature becomes lower than the electron mass, while the slightly smaller present Hubble parameter and the electron mass are indicated if the BBN data are taken into account. We also find that the baryon density is more stringently constrained by the baryon acoustic oscillation data rather than the BBN. We have derived the ratio of the electron mass at early Universe and the present $m_e/m_{e0}=1.0028\pm 0.0064$ and $H_0=68.0\pm 1.1\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$.

The cosmological observations of cosmic microwave background and large-scale structure indicate that our universe has a nearly scaling invariant power spectrum of the primordial perturbation. However, the exact origin for this primordial spectrum is still unclear. Here, we propose the Weyl scaling invariant $R^2+R^3$ gravity that gives rise to inflation that is responsible for the primordial perturbation in the early universe. We develop both analytic and numerical treatments on inflationary observables, and find this model gives a distinctive scalar potential that can support two different patterns of inflation. The first one is similar to that occurs in the pure $R^2$ model, but with a wide range of tensor-to-scalar ratio $r$ from $\mathcal{O}({10}^{-4})$ to $\mathcal{O}({10}^{-2})$. The other one is a new situation with not only slow-roll inflation but also a short stage of oscillation-induced accelerating expansion. Both patterns of inflation have viable parameter spaces that can be probed by future experiments on cosmic microwave background and primordial gravitational waves.

In the scenario in which QCD axion dark matter is produced after inflation, the Universe is populated by large inhomogeneities on very small scales. Eventually, these fluctuations will collapse gravitationally to form dense axion miniclusters that trap up to $\sim 75\%$ of the dark matter within asteroid-mass clumps. Axion miniclusters are physically tiny however, so haloscope experiments searching for axions directly on Earth are much more likely to be probing “minivoids”—the space in between miniclusters. This scenario seems like it ought to spell doom for haloscopes, but while these minivoids might be underdense, they are not totally devoid of axions. Using Schrödinger-Poisson and $N$-body simulations to evolve from realistic initial field configurations, we quantify the extent to which the local ambient dark matter density is suppressed in the postinflationary scenario. We find that a typical experimental measurement will sample an axion density that is only around 10% of the expected galactic dark matter density. Our results are taken as conservative estimates and have implications for experimental campaigns lasting longer than a few years, as well as broadband haloscopes that have sensitivity to transient signatures. We show that for a $\mathcal{O}(\mathrm{year})$-long integration times, the measured dark matter density should be expected to vary by 20%–30%.

Black-hole spectroscopy, that is, measuring the characteristic frequencies and damping times of different modes in a black-hole ringdown, is a powerful probe for testing deviations from the general theory of relativity (GR). In this work, we present a comprehensive study on its ability to identify deviations from the spectrum of a Kerr black hole in GR. Specifically, we investigate the performance of black hole spectroscopy on a diverse set of theoretically motivated as well as phenomenologically modified spectra. We find that while the signal-to-noise ratio ${\rho }_{\mathrm{RD}}$ in the ringdown required to identify a modification to the GR Kerr black hole spectrum depends on the details of the modifications, a modification that introduces $\sim 1\%$ shift in the fundamental mode frequencies can typically be distinguished with ${\rho }_{\mathrm{RD}}\in [150,500]$. This range of ${\rho }_{\mathrm{RD}}$ is feasible with the next-generation detectors, showing a promising science case for black hole spectroscopy.

We propose a novel idea to detect a dark photon in gravitational wave experiments. Our setups are capable of performing the whole process of dark photon production, its decay products, and new physics signal discovery. This “mini-LHC” is inspired by the recent idea of dark photon detection using laser light in light shining through the wall (LSW) experiments such as ALPS II. Taking the subfrequency light emitted from the laser source as the new physics signal, we show that the sensitivity of our proposal is 2 orders of magnitude better than the original idea in the LSW studies.

We formulate a Lagrangian hydrodynamics including shear and bulk viscosity in the presence of spin density, and investigate it using the linear response functional formalism. The result is a careful accounting of all sound and vortex interactions close to local equilibrium. In particular, we demonstrate that the mixing of sound waves and vortices via polarization, first observed in the ideal fluid limit, extends to the shear mode once dissipative effects are included. This provides a realization within Lagrangian hydrodynamics of the symmetric shear polarization contribution recently advocated from transport and Zubarev approaches as well as phenomenological considerations. Once causal relaxational dynamics is included, this effect, seemingly puzzling because it results in a nondissipative coupling between a transient mode to an equilibrium quantity, can be understood as a competition between the Israel-Stewart and the polarization relaxation timescale, and a breakdown of local Markovianity. We close by discussing phenomenological implications of these results.

We calculate total and differential cross sections for the pair production, at the Large Hadron Collider, of exotic leptons that could emerge from models with vectorlike leptons and in type-III seesaw scenarios. Our predictions include next-to-leading-order QCD corrections, and we subsequently match them with either parton showers, or threshold resummation at the next-to-next-to-leading logarithmic accuracy. Our results show an important increase of the cross sections relative to the leading-order predictions, exhibit a distortion of the shapes for various differential distributions, and feature a significant reduction of the scale uncertainties. Our predictions have been obtained from new feynrules model implementations and associated Universal FeynRules Output (UFO) model libraries. This completes the set of next-to-leading-order implementations of new physics models featuring extra leptons that are publicly available on the feynrules model database.

The $R_{D^{(*)}}$ anomaly is one of the most intriguing experimental results in particle physics today. Experiments such as BABAR, Belle and LHCb have measured a consistent tension with the Standard Model (SM). We study several extensions of the SM that could potentially explain this tension, such as production of heavy ${\mathrm{W}}^{\prime }$ bosons, under the sequential SM scenario, leptoquarks with preferential couplings to third-generation fermions, and interpretations through effective field theories. Such models are not only able to explain the $R_{D^{(*)}}$ anomaly, but also to produce distinctive signatures at the LHC. We present different feasibility studies to probe each of these scenarios at the LHC, considering final states with one b-quark candidate, one hadronically decaying tau lepton (${\tau }_h$) and missing transverse momentum ($p_{\mathrm{T}}^{\mathrm{miss}}$). The selection criteria have been optimized for each model to achieve best signal significance. The studies are performed considering different LHC running conditions, at $\sqrt{s}=13$ and 13.6 TeV, and different luminosities (150 and $3000{\mathrm{fb}}^{-1}$).