We consider a class of gauged $U(1)$ extensions of the Standard Model (SM), where the light neutrino masses are generated by an inverse seesaw mechanism. In addition to the three right handed neutrinos, we add three singlet fermions and demand an extra $Z_2$ symmetry under which, the third generations of both of the neutral fermions are odd, which in turn gives us a stable dark matter candidate. We express the $U(1)$ charges of all the fermions in terms of the $U(1)$ charges of the standard model Higgs and the new complex scalar. We study the bounds on the parameters of the model from vacuum stability, perturbative unitarity, dark matter relic density, and direct detection constraints. We also obtain the collider constraints on the $Z^{\prime }$ mass and the $U(1{)}^{\prime }$ gauge coupling. Finally, we compare all the bounds on the $Z^{\prime }$ mass versus the $U(1{)}^{\prime }$ gauge coupling plane.

In light of recent data, we study the new physics effects in the exclusive $b\to s{\ell }^{+}{\ell }^{-}$ decays from a model independent perspective. Different combinations of the dimension six effective operators along with their respective Wilson coefficients are chosen for the analysis. To find out the operator or sets of operators that can best explain the available data in this channel, we simultaneously apply popular model selection tools like cross-validation and the information theoretic approach like Akaike information criterion (AIC). There are one, two, and three-operator scenarios which survive the test and a left-handed quark current with vector muon coupling is common among them. This is also the only surviving one-operator scenario. Best-fit values and correlations of the new Wilson coefficients are supplied for all the selected scenarios. We find that the angular observables play the dominant role in the model selection procedure. We also note that while a left-handed quark current with axial-vector muon coupling is the only one-operator scenario able to explain the ratios $R_{K^{(*)}}$ ($R_{K^{*}}$ for $q^2\in [0.045,1.1]{\mathrm{GeV}}^2$ in particular), there are also a couple of two operator scenarios that can simultaneously explain the measured $R_{K^{(*)}}$.

The mirror twin Higgs (MTH) addresses the little hierarchy problem by relating every Standard Model (SM) particle to a twin copy, but is in tension with cosmological bounds on light degrees of freedom. Asymmetric reheating has recently been proposed as a simple way to fix MTH cosmology by diluting the twin energy density. We show that this dilution sets the stage for an interesting freeze-in scenario where both the initial absence of dark sector energy and the feeble coupling to the SM are motivated for reasons unrelated to dark matter production. We give the twin photon a Stueckelberg mass and freeze-in twin electron and positron dark matter through the kinetic mixing portal. The kinetic mixing required to obtain the dark matter abundance is of the loop-suppressed order expected from infrared contributions in the MTH.

The complex 2HDM (C2HDM) is the most general CP-violating two Higgs-doublet-model that possesses a softly broken ${\mathbb{Z}}_2$ symmetry. However, the physical consequences of the model cannot depend on the basis of scalar fields used to define it. Thus, to get a better sense of the significance of the C2HDM parameters, we have analyzed this model by employing a basis-independent formalism. This formalism involves transforming to the Higgs basis (which is defined up to an arbitrary complex phase) and identifying quantities that are invariant with respect to this phase degree of freedom. Using this method, we have obtained the constraints that enforce the softly broken ${\mathbb{Z}}_2$ symmetry. One can then relate the C2HDM parameters to basis-independent quantities up to a twofold ambiguity. We then show how this remaining ambiguity is resolved. We also examine the possibility of spontaneous CP violation when the scalar potential of the C2HDM is explicitly CP conserving. Basis-independent constraints are presented that govern the presence of spontaneous CP violation.

We construct a flavor model in an anti-SU(5) grand unified theory with a tetrahedral symmetry $A_4$. We choose a basis where $Q_{\text{em}}=-\frac{1}{3}$ quarks and charged leptons are already mass eigenstates. This choice is possible from the $A_4$ symmetry. Then, matter representation ${\overline{\mathbf{10}}}_{-1}^{\text{matter}}$ contains both a quark doublet and a heavy neutrino $N$, which enables us to use the $A_4$ symmetry to both $Q_{\text{em}}=+\frac{2}{3}$ quark masses and neutrino masses (through the see saw via $N$). This is made possible because the anti-SU(5) breaking is achieved by the Higgs fields transforming as antisymmetric representations of SU(5), ${\overline{\mathbf{10}}}_{-1}^H\oplus {\mathbf{10}}_{+1}^H$, reducing the rank-5 anti-SU(5) group down to the rank-4 standard model group $\mathrm{SU}(3{)}_C\times \mathrm{SU}(2{)}_W\times \mathrm{U}(1{)}_Y$. For possible mass matrices, the $A_4$ symmetry predictions on mass matrices at field theory level are derived. Finally, an illustration from string compactification is presented.

In light of the recent CMS analysis on lepton flavor violating (LFV) heavy Higgs searches and updated bounds on various search channels involving neutral and charged scalars, we provide the updated constraints on the Type-III two-Higgs-doublet model (2HDM) with a $\tau -\mu$ LFV. In doing so, we first extend the CMS analysis to cover the mass region below 200 GeV by recasting their data. After obtaining the bounds on the heavy Higgs production in the mass range between 130 and 450 GeV, we analyze the parameter space of the Type-III 2HDM with various scenarios of mass spectrum and heavy Higgs production strengths. We found that in most scenarios, searching for the heavy Higgs in the mass range lower than $2m_W$ is very important in constraining the parameter space of the Type-III 2HDM. Hence, we suggest for future analysis that the search window for the LFV heavy Higgs be extended to the lower mass region.

Strong three-body interactions above threshold govern the dynamics of many exotics and conventional excited mesons and baryons. Three-body finite-volume energies calculated from lattice QCD promise an ab initio understanding of these systems. We calculate the three-${\pi }^{+}$ spectrum unraveling the three-body dynamics that is tightly intertwined with the $S$-matrix principle of three-body unitarity and compare it with recent lattice QCD results. For this purpose, we develop a formalism for three-body systems in moving frames and apply it numerically.

We give a systematic study of ${\mathbf{B}}_c\to {\mathbf{B}}_{n}V$ decays, where ${\mathbf{B}}_c$ and ${\mathbf{B}}_n$ correspond to the antitriplet charmed and octet baryons, respectively, while $V$ stands for the vector mesons. We calculate the color-symmetric contributions to the decays from the effective Hamiltonian with the factorization approach and extract the antisymmetric ones based on the experimental measurements and $SU(3{)}_F$ flavor symmetry. We find that most of the existing experimental data for ${\mathbf{B}}_c\to {\mathbf{B}}_{n}V$ are consistent with our fitting results. We present all the branching ratios of the Cabibbo allowed, singly Cabibbo suppressed, and doubly Cabibbo suppressed decays of ${\mathbf{B}}_c\to {\mathbf{B}}_{n}V$. The decay parameters for the daughter baryons and mesons in ${\mathbf{B}}_c\to {\mathbf{B}}_{n}V$ are also evaluated. In particular, we point out that the Cabibbo allowed decays of ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Lambda }}^0{\rho }^{+}$ and ${\mathrm{\Xi }}_c^0\to {\mathrm{\Xi }}^{-}{\rho }^{+}$ as well as the singly Cabibbo suppressed ones of ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Lambda }}^0{K}^{*+}$, ${\mathrm{\Xi }}_c^{+}\to {\mathrm{\Sigma }}^{+}\varphi$, and ${\mathrm{\Xi }}_c^0\to {\mathrm{\Xi }}^{-}{K}^{*+}$ have large branching ratios and decay parameters with small uncertainties, which can be tested by the experimental searches at the charm facilities.

Solutions describing holographic surface defects in $D=5$, $N=4$ gauged supergravity theories are constructed. It is shown that a surface defect solution in pure Romans’s gauged supergravity is singular. Adding a single vector multiplet allows for the construction of a nonsingular solution. The on-shell action and one point functions of operators in the presence of the defect are computed using holographic renormalization.

Binary neutron star mergers can be sources of gravitational waves coincident with electromagnetic counterpart emission across the spectrum. To solidify their role as multimessenger sources, we present fully 3D, general relativistic, magnetohydrodynamic simulations of highly spinning binary neutrons stars initially on quasicircular orbits that merge and undergo delayed collapse to a black hole. The binaries consist of two identical stars modeled as $\mathrm{\Gamma }=2$ polytropes with spin ${\chi }_{\mathrm{NS}}=0.36$ aligned along the direction of the total orbital angular momentum $L$. Each star is initially threaded by a dynamical unimportant interior dipole magnetic field. The field is extended into the exterior where a nearly force-free magnetosphere resembles that of a pulsar. The magnetic dipole moment $\mu$ is either aligned or perpendicular to $L$ and has the same initial magnitude for each orientation. For comparison, we also impose symmetry across the orbital plane in one case where $\mu$ in both stars is aligned along $L$. We find that the lifetime of the transient hypermassive neutron star remnant, the jet launching time, and the ejecta (which can give rise to a detectable kilonova) are very sensitive to the magnetic field orientation. By contrast, the physical properties of the black $\mathrm{hole}+\text{disk remnant}$, such as the mass and spin of the black hole, the accretion rate, and the electromagnetic (Poynting) luminosity, are roughly independent of the initial magnetic field orientation. In addition, we find imposing symmetry across the orbital plane does not play a significant role in the final outcome of the mergers. Our results suggest that, as in the black hole-neutron star merger scenario, an incipient jet emerges only when the seed magnetic field has a sufficiently large-scale poloidal component aligned to the initial orbital angular momentum. The lifetime [$\mathrm{\Delta }t\gtrsim 140(M_{\mathrm{NS}}/1.625M_{\odot })\mathrm{ms}$] and Poynting luminosities [$L_{\mathrm{EM}}\simeq {10}^{52}\mathrm{erg}/\mathrm{s}$] of the jet, when it forms, are consistent with typical short gamma-ray bursts, as well as with the Blandford-Znajek mechanism for launching jets.

The deterministic nature of general relativity is ensured by the strong cosmic censorship conjecture, which asserts that spacetime cannot be extended beyond the Cauchy horizon with the square integrable connection. Although this conjecture holds true for asymptotically flat black hole spacetimes in general relativity, a potential violation of this conjecture occurs in charged asymptotically de Sitter spacetimes. Since it is expected that the Einstein-Hilbert action will involve higher curvature corrections, in this article we have studied whether one can restore faith in the strong cosmic censorship when higher curvature corrections to general relativity are considered. Contrary to our expectations, we have explicitly demonstrated that not only a violation to the conjecture occurs near extremality, but the violation appears to become stronger as the strength of the higher curvature term increases.

We determine for the first time in the literature the analytic form of the Rayleigh potential of the general relativistic Poynting-Robertson effect. The employed procedure is based on the use of an integrating factor and a new integration strategy where the test particle’s dissipated energy represents the fundamental variable. The obtained results and their implications are discussed. Finally, concluding remarks and future projects are drawn.

We develop the nonlinear statistics of primordial black holes generated by a Gaussian spectrum of primordial curvature perturbations. This is done by employing the compaction function as the main statistical variable under the constraints that (i) the overdensity has a high peak at a point ${\overrightarrow{x}}_0$, (ii) the compaction function has a maximum at a smoothing scale $R$, and finally, (iii) the compaction function amplitude at its maximum is higher than the threshold necessary to trigger a gravitational collapse into a black hole of the initial overdensity. Our calculation allows for the fact that the patches which are destined to form PBHs may have a variety of profile shapes and sizes. The predicted PBH abundances depend on the power spectrum of primordial fluctuations. For a very peaked power spectrum, our nonlinear statistics, the one based on the linear overdensity and the one based on the use of curvature perturbations, all predict a narrow distribution of PBH masses and comparable abundance. For broader power spectra, the linear overdensity statistics overestimate the abundance of primordial black holes while the curvature-based approach under-estimates it. Additionally, for very large smoothing scales, the abundance is no longer dominated by the contribution of a mean overdensity but rather by the whole statistical realizations of it.

In an open quantum system, we study the evolution of a two-level atom as a detector which interacts with given environments. For a uniformly accelerated two-level atom coupled to a massless scalar field in the Minkowski vacuum, when it evolves for a certain time, we find that there exists a peak value for the quantum Fisher information (QFI) of acceleration, which indicates that the optimal precision of estimation is achieved when choosing an appropriate acceleration $a$. QFI has different behaviors for different initial state parameters $\theta$ of the atom, displaying periodicity. However, the periodicity fades away with the evolution of time, which means that the initial state cannot affect the later stable quantum state. Furthermore, adding a boundary, we observe that the peak value of QFI increases when the atom is close to the boundary, which shows that QFI is protected by the boundary. Here, QFI fluctuates, and there may exist two peak values with a certain moment, which expands the detection range of the acceleration. Therefore, we can enhance the estimation precision of acceleration by choosing an appropriate position and acceleration $a$. The periodicity of QFI with respect to the initial state parameter $\theta$ lasts a longer time than the previous unbounded case, which indicates that the initial state is protected by the boundary. Finally, for a thermal bath with a boundary, QFI of temperature has no more than one peak value with a certain moment, which is different from QFI of acceleration with a boundary. The periodicity also lasts a longer time than unbounded case, which shows the initial quantum state of the atom is protected by the boundary for two cases.

We obtain constraints on the Yukawa-type corrections to Newton’s gravitational law and on the coupling constant of axionlike particles to nucleons following from the experiment on measuring the Casimir force between a Au-coated microsphere and a silicon carbide plate. For this purpose, both the Yukawa-type force and the force due to two-axion exchange between nucleons are calculated in the experimental configuration. In the interaction range of Yukawa force exceeding 1 nm and for axion masses above 17.8 eV, the obtained constraints are much stronger than those found previously from measuring the lateral Casimir force between sinusoidally corrugated surfaces. These results are compared with the results of other laboratory experiments on constraining non-Newtonian gravity and axionlike particles in the relevant interaction ranges.

In this work, we seriously discuss whether $X(3915)$ can be treated as a ${\chi }_{c0}(2P)$ state. Based on an unquenched quark model, we give the mass spectrum of the ${\chi }_{cJ}(2P)$ states, where there are no free input parameters in our calculation. Our result shows that the mass gap between ${\chi }_{c0}(2P)$ and ${\chi }_{c2}(2P)$ can reach 13 MeV, which can reproduce the mass difference between $Z(3930)$ and $X(3915)$. Additionally, the calculated masses of ${\chi }_{c0}(2P)$ and ${\chi }_{c2}(2P)$ are consistent with experimental values of $X(3915)$ and $Z(3930)$, respectively. Besides, giving the mass spectrum analysis to support $X(3915)$ as ${\chi }_{c0}(2P)$, we also calculate the width of ${\chi }_{c0}(2P)$ with the same framework, which is also consistent with the experimental data of $X(3915)$. Thus, the possibility of charmoniumlike state $X(3915)$ as ${\chi }_{c0}(2P)$ state is further enforced.

We consider anisotropic cosmologies in a particular shift-symmetric Horndeski theory containing the $G^{\mu \nu }{\partial }_{\mu }\varphi {\partial }_{\nu }\varphi$ coupling, where $G^{\mu \nu }$ is the Einstein tensor. This theory admits stable in the future self-accelerating cosmologies whose tensor perturbations propagate with the velocity very close to the speed of light such that the theory agrees with the gravity wave observations. Surprisingly, we find that the anisotropies within the Bianchi I homogeneous spacetime model are screened at early time by the scalar charge, whereas at late times they are damped in the usual way. Therefore, contrary to what one would normally expect, the early state of the universe in the theory cannot be anisotropic and (locally) homogeneous in the absence of spatial curvature. The early universe cannot be isotropic either, because it should then be unstable with respect to inhomogeneous perturbations. As a result, the early universe should be inhomogeneous. At the same time, we find that in the spatially curved Bianchi IX case the anisotropies can be strong at early times even in the presence of a scalar charge.

We present 48 further examples, in addition to the 10 identified in [1], of ghost-and-tachyon-free critical cases of parity-conserving Poincaré gauge theories of gravity (${\mathrm{PGT}}^{+}$) that are also power-counting renormalizable (PCR). This is achieved by extending the range of critical cases considered. Of the new PCR theories, seven have 2 massless degrees of freedom (d.o.f.) in propagating modes and a massive $0^{-}$ or $2^{-}$ mode, eight have only 2 massless d.o.f., and 33 have only massive mode(s). We also clarify the treatment of nonpropagating modes in determining whether a theory is PCR.

Bayesian inference of gravitational wave signals is subject to systematic error due to modeling uncertainty in waveform signal models coined approximants. A growing collection of approximants are available which use different approaches and make different assumptions to ease the process of model development. We provide a method to marginalize over the uncertainty in a set of waveform approximants by constructing a mixture-model multiwaveform likelihood. This method fits into existing workflows by determining the mixture parameters from the per-waveform evidence, enabling the production of marginalized combined sample sets from independent runs.

An early matter-dominated (eMD) era may have preceded the standard radiation-dominated era. During an eMD era, primordial black holes (PBHs) can be formed due to the gravitational collapse of a fraction of high-density peaks. If their formation probability is sufficiently high, PBHs formed during an eMD era could play interesting cosmological roles, such as accounting for part of or entire dark matter, and/or causing PBH mergers which might have been or would be detected by ongoing and future gravitational-wave detectors. In addition to PBHs, gravitationally collapsed, virialized objects can also be formed during an eMD era. We discuss gravitational waves associated with the formation of such collapsed structures when PBH formation probability is relatively high during an eMD era, and show that such GWs can be observable in future.