We show that the gravitational wave signals from primordial black hole (PBH) binaries at high redshift can be detected. The detectability of PBH binaries is enhanced by redshift bias and more PBH binaries at high redshift. The initial clustering of PBHs is also included and enhances the effectively detectable mass ranges of PBHs at high redshift. Future observations on the gravitational wave at high redshift by space-based detectors such as the Laser Interferometer Space Antenna (LISA) and Square Kilometre Array (SKA) can constrain the fraction of PBHs in dark matter and PBHs initial distribution.

We investigate the possible existence of anomalous mass defects in the low mass region of stellar sequences of strange stars. We employ the nonperturbative equation of state derived in the framework of the field correlator method to describe the hydrostatic equilibrium of the strange matter. The large distance static $Q\overline{Q}$ potential $V_1$ and the gluon condensate $G_2$ are the main parameters of the model. We use the surface gravitational redshift measurements as a probe to determine the ratio $(\mathcal{P}/\mathcal{E}{)}_C$ at the center of strange stars. For $V_1=0$ and $G_2\gtrsim 0.035{\mathrm{GeV}}^4$, we show that $(\mathcal{P}/\mathcal{E}{)}_C\simeq 0.262$ and the corresponding redshift $z_S\simeq 0.47$ are limiting values at the maximum mass of the highest mass stellar sequence. As a direct application of our study, we try to determine the values of $V_1$ and $G_2$ from astrophysical observations of the compact star 1E 1207.4-5209. Due to the uncertainties in the surface redshift determination, we made two attempts to obtain the model parameters. Our findings show that $(\mathcal{P}/\mathcal{E}{)}_C=0.073_{+0.024}^{+0.029}$ at 68% confidence, $V_1=0.44\pm 0.10\mathrm{GeV}$ at 90% confidence and $G_2=0.008\pm 0.001{\mathrm{GeV}}^4$ at 95% confidence in the first attempt; and $(\mathcal{P}/\mathcal{E}{)}_C=0.087\pm 0.028$ at 71% confidence, $V_1=0.43\pm 0.085\mathrm{GeV}$ at 94% confidence and $G_2=0.0093\pm 0.00092{\mathrm{GeV}}^4$ at 94% confidence in the second attempt. These values of $V_1$ and $G_2$ are in reasonable agreement with the lattice and QCD sum rules calculations. As a consequence of the high values of $V_1$ and $G_2$, the anomalous mass defects of 1E 1207.4-5209 are $|{\mathrm{\Delta }}_{2}M|\simeq 2.56\times {10}^{53}\mathrm{erg}$ in the first attempt and $|{\mathrm{\Delta }}_{2}M|\simeq 2.94\times {10}^{53}\mathrm{erg}$ in the second attempt.

The Laser Interferometer Space Antenna (LISA) mission, scheduled for launch in the early 2030s, is a gravitational wave observatory in space designed to detect sources emitting in the millihertz band. In contrast to the present ground-based detectors, the LISA data are expected to be a signal dominated, with strong and weak gravitational wave signals overlapping in time and in frequency. Astrophysical population models predict a sufficient number of signals in the LISA band to blend together and form an irresolvable foreground noise. In this work, we present a generic method for characterizing the foreground signals originating from a given astrophysical population of coalescing compact binaries. Assuming idealized detector conditions and a perfect data analysis technique capable of identifying and removing the bright sources, we apply an iterative procedure which allows us to predict the different levels of foreground noise.

We examine the propagation and flavor oscillations of neutrinos under the influence of gravitational waves (GWs) with an arbitrary polarization. We rederive the effective Hamiltonian for the system of three neutrino flavors using the perturbative approach. Then, using this result, we consider the evolution of neutrino flavors in stochastic GWs with a general energy density spectrum. The equation for the density matrix is obtained and solved analytically in the case of three neutrino flavors. As an application, we study the evolution of the flavor content of a neutrino beam emitted in a core-collapsing supernova. We obtain the analytical expressions for the contributions of GWs to the neutrino fluxes and for the damping decrement, which describes the attenuation of the fluxes to their asymptotic values. We find that the contribution to the evolution of neutrino fluxes from GWs, emitted by merging supermassive black holes, dominates over that from black holes with stellar masses. The implication of the obtained results for the measurement of astrophysical neutrinos with neutrino telescopes is discussed.

We show how in the standard electroweak model three $SU(2{)}_L$ Nambu monopoles, each carrying electromagnetic (EM) and $Z$ magnetic fluxes, can merge (through $Z$ strings) with a single $U(1{)}_Y$ Dirac monopole to yield a composite monopole that only carries EM magnetic flux. Compatibility with the Dirac quantization condition requires this composite monopole to carry six quanta ($12\pi /e$) of magnetic charge, independent of the electroweak mixing angle ${\theta }_w$. The Dirac monopole is not regular at the origin and the energy of the composite monopole is therefore divergent. We discuss how this problem is cured by embedding $U(1{)}_Y$ in a grand unified group such as $SU(5)$. A second composite configuration with only one Nambu monopole and a colored $U(1{)}_Y$ Dirac monopole that has minimal EM charge of $4\pi /e$ is also described. Finally, there exists a configuration with an EM charge of $8\pi /e$ as well as screened color magnetic charge.

Confining dark sectors at the GeV scale can lead to novel collider signatures including those termed emerging jets with large numbers of displaced vertices. The triggers at the LHC experiments were not designed with this type of new physics in mind, and triggering can be challenging, especially if the mediator is relatively light and/or has quantum numbers such that additional jets are not automatically produced in each event. We show that the efficiency and the total event rate at current triggers can be significantly improved by considering initial state radiation of the events, with the largest increase in rate coming from simulation of two additional jets. We also explore possible new triggers that employ hit counts in different tracker layers as input into a machine learning algorithm. We show that these new triggers can have reasonably low background rates, and that they are sensitive to a wide range of new physics parameters even when trained on a single model.

Motivated by the fermion mass hierarchy, we study the phenomenology of two flavorful two-Higgs-doublet model (2HDM) scenarios. By virtue of the flavor or singular alignment ansatz, it is possible to link the mass of a subset of fermions to the vacuum expectation value (VEV) of a unique Higgs doublet and to simultaneously avoid flavor-changing-neutral-currents at tree level. We explicitly construct two models called Type A and B. There, either the top quark alone or all third generation fermions couple to the doublet with the larger VEV. The other fermions acquire their masses through the small VEV of the other doublet. Thus, more natural values for the Yukawa couplings can be obtained. The main differences between these models and conventional ones are studied, including a discussion of both their structure and phenomenological consequences. In particular, as distinctive deviations for the Yukawa couplings of the light fermions are predicted, we discuss possible tests at the LHC based on searches for $h\to J/\mathrm{\Psi }+\gamma$, $h\to \mu \mu$ and heavy scalar resonances decaying to muon pairs. We find that for a wide region of parameter space, this specific set of signatures can be used to distinguish among the new proposed types and the conventional ones.

We study reported deviations between observations and theoretical predictions associated with the production of a pair of dileptonically decaying top quarks at the LHC, and we examine the possibility that they reflect a signal of toponium formation. We investigate the production by gluon fusion of a color-singlet spin-0 toponium ${\eta }_t$ bound state of a top and antitop quark, that then decays dileptonically ($gg\to {\eta }_t\to \overline{\ell }\ell b\overline{b}\nu \overline{\nu }$). We find strong correlations favoring the production of dilepton systems featuring a small angular separation in azimuth and a small invariant mass. Although toponium production only contributes to 0.8% of the total top-quark pair-production cross section at the 13 TeV LHC, there is a possibility that it can account for observed excesses in the narrow edges of phase space. We propose a method to discover toponium formation by “reconstructing” both its top and antitop quark constituents in the dilepton channel.

The process $e^{+}{e}^{-}\to \varphi \eta$ is studied at 22 center-of-mass energy points ($\sqrt{s}$) between 2.00 and 3.08 GeV using $715{\mathrm{pb}}^{-1}$ of data collected with the BESIII detector. The measured Born cross section of $e^{+}{e}^{-}\to \varphi \eta$ is found to be consistent with BABAR measurements, but with improved precision. A resonant structure around 2.175 GeV is observed with a significance of $6.9\sigma$ with mass $(2163.5\pm 6.2\pm 3.0)\mathrm{MeV}/c^2$ and width $({31.1}_{-11.6}^{+21.1}\pm 1.1)\mathrm{MeV}$, where the first uncertainties are statistical and the second are systematic.

Many new physics models, including versions of supersymmetry characterized by $R$-parity violation (RPV), compressed mass spectra, long decay chains, or additional hidden sectors, predict the production of events with top quarks, low missing transverse momentum, and many additional quarks or gluons. The results of a search for new physics in events with two top quarks and additional jets are reported. The search is performed using events with at least seven jets and exactly one electron or muon. No requirement on missing transverse momentum is imposed. The study is based on a sample of proton-proton collisions at $\sqrt{s}=13\text{TeV}$ corresponding to $137{\mathrm{fb}}^{-1}$ of integrated luminosity collected with the CMS detector at the LHC in 2016–2018. The data are used to determine best fit values and upper limits on the cross section for pair production of top squarks in scenarios of RPV and stealth supersymmetry. Top squark masses up to 670 $(870)\text{GeV}$ are excluded at 95% confidence level for the RPV (stealth) scenario, and the maximum observed local signal significance is 2.8 standard deviations for the RPV scenario with top squark mass of $400\text{GeV}$.

The ratio of the $B_s^0$ and $B^0$ fragmentation fractions, $f_s/f_d$, in proton-proton collisions at the LHC, is obtained as a function of $B$-meson transverse momentum and collision center-of-mass energy from the combined analysis of different $B$-decay channels measured by the LHCb experiment. The results are described by a linear function of the meson transverse momentum or with a function inspired by Tsallis statistics. Precise measurements of the branching fractions of the $B_s^0\to J/\psi \varphi$ and $B_s^0\to D_s^{-}{\pi }^{+}$ decays are performed, reducing their uncertainty by about a factor of 2 with respect to previous world averages. Numerous $B_s^0$ decay branching fractions, measured at the LHCb experiment, are also updated using the new values of $f_s/f_d$ and branching fractions of normalization channels. These results reduce a major source of systematic uncertainty in several searches for new physics performed through measurements of $B_s^0$ branching fractions.

In this work we consider the generalized zeta function method to obtain temperature corrections to the vacuum (Casimir) energy density, at zero temperature, associated with quantum vacuum fluctuations of a scalar field subjected to a helix boundary condition and whose modes propagate in ($3+1$)-dimensional Euclidean spacetime. We find closed and analytical expressions for both the two-point heat kernel function and free energy density in the massive and massless scalar field cases. In particular, for the massless scalar field case, we also calculate the thermodynamics quantities internal energy density and entropy density, with their corresponding high- and low-temperature limits. We show that the temperature correction term in the free energy density must suffer a finite renormalization, by subtracting the scalar thermal blackbody radiation contribution, in order to provide the correct classical limit at high temperatures. We check that, at low temperature, the entropy density vanishes as the temperature goes to zero, in accordance with the third law of thermodynamics. We also point out that, at low temperatures, the dominant term in the free energy and internal energy densities is the vacuum energy density at zero temperature. Finally, we also show that the pressure obeys an equation of state.

Near-horizon symmetries are studied for static black hole solutions to Einstein equations containing a supertranslation field. A supertranslation field is defined at the unit sphere. We consider general diffeomorphisms which preserve the gauge and the near-horizon structure of the metric. Diffeomorphisms are generated by the vector fields and form a group of near-horizon symmetries. The densities of variation of the surface charge associated to horizon symmetries of the metric are calculated in different coordinate systems connected by “large” transformations containing a supertranslation field in the metric. Variations of the surface charge corresponding to horizon symmetries are calculated in different coordinate systems. It is shown that the variations of the charge in systems connected by a large transformation have different integrability properties over the space of metrics. In the case of a supertranslation field depending only on the spherical angle $\theta$ it is shown that, although the variations of the surface charge in two coordinate systems connected by a large transformation are equal to each other, in one coordinate system the charge variation, having the form of variation of a functional of metrics, is integrable, but in another system it is not.

We propose a new method for probing inflationary models of primordial black hole (PBH) production, using only CMB physics at relatively large scales. In PBH scenarios, the primordial power spectrum profile for curvature perturbations is characterized by a pronounced dip, followed by a rapid growth toward small scales, leading to a peak responsible for PBH formation. We focus on scales around the dip that are well separated from the peak to analytically compute expressions for the curvature power spectrum and bispectrum. The size of the squeezed bispectrum is enhanced at the position of the dip, and it acquires a characteristic scale dependence that can be probed by cross correlating CMB $\mu$-distortions and temperature fluctuations. We quantitatively study the properties of such cross correlations and how they depend on the underlying model, discussing how they can be tested by the next generation of CMB $\mu$-distortion experiments. This method allows one to experimentally probe inflationary PBH scenarios using well-understood CMB physics, without considering nonlinearities associated with PBH formation and evolution.

In the gravitational effective theories including higher curvature terms, cosmological solutions can have nontrivial de Sitter fixed points. We study phenomenological implications of such points, focusing on a theory in which a massive scalar field is nonminimally coupled to the Euler density. We first analyze the phase portrait of the dynamical system and show that the fixed point can be a sink or a saddle, depending on the strength of the coupling. Then, we compute the perturbation spectra generated in the vicinity of the fixed point in order to investigate whether the fixed point may be considered as cosmic inflation. We find parameter regions that are consistent with the cosmological data, given that the anisotropies in the cosmic microwave background are seeded by the fluctuations generated near the fixed point. Future observation may be used to further constrain the coupling function of this model. We also comment briefly on the swampland conjecture.

One or more scalar leptoquarks with masses around a few TeV may provide a solution to some of the flavor anomalies that have been observed. We discuss the impact of such new degrees on baryon number violation when the theory is embedded in a Pati-Salam model. The Pati-Salam embedding can suppress renormalizable and dimension-five baryon number violation in some cases. Our work extends the results of Assad, Grinstein, and Fornal who considered the same issue for vector leptoquarks.

Recently, the LHCb Collaboration reported on the evidence for a hidden charm pentaquark state with strangeness, i.e., $P_{cs}(4459)$, in the $J/\psi \mathrm{\Lambda }$ invariant mass distribution of the ${\mathrm{\Xi }}_b^{-}\to J/\psi \mathrm{\Lambda }{K}^{-}$ decay. In this work, assuming that $P_{cs}(4459)$ is a ${\overline{D}}^{*}{\mathrm{\Xi }}_c$ molecular state, we study this decay via triangle diagrams ${\mathrm{\Xi }}_b\to {\overline{D}}_s^{(*)}{\mathrm{\Xi }}_c\to ({\overline{D}}^{(*)}\overline{K}){\mathrm{\Xi }}_c\to P_{cs}\overline{K}\to (J/\psi \mathrm{\Lambda })\overline{K}$. Our study shows that the production yield of a spin $3/2$ ${\overline{D}}^{*}{\mathrm{\Xi }}_c$ state is approximately one order of magnitude larger than that of a spin $1/2$ state due to the interference of ${\overline{D}}_s{\mathrm{\Xi }}_c$ and ${\overline{D}}_s^{*}{\mathrm{\Xi }}_c$ intermediate states. We obtain a model independent constraint on the product of couplings $g_{P_{cs}{\overline{D}}^{*}{\mathrm{\Xi }}_c}$ and $g_{P_{cs}J/\psi \mathrm{\Lambda }}$. With the predictions of two particular molecular models as inputs, we calculate the branching ratio of ${\mathrm{\Xi }}_b^{-}\to (P_{cs}\to )J/\psi \mathrm{\Lambda }{K}^{-}$ and compare it with the experimental measurement. We further predict the line shape of this decay that could be useful to future experimental studies.

In this work, we argue that the observed differences in the value of the vector coupling constant extracted from the decays $\rho \to \pi \pi$ ($g_{\rho }=6.0$), $\rho \to l^{+}{l}^{-}$ ($g_{\rho }=5.0$) and $\omega \to l^{+}{l}^{-}$ ($g_{\rho }=5.7$), where $l=e$, $\mu$, are an indication of the important role played by the $1/N_c$ corrections in the description of these processes. We show that an emission of a photon by charged meson loops in the ${\rho }^0,\omega ,\varphi \to \gamma$ transitions is a key process that allows to describe above vector meson decays into two leptons with a single value $g_{\rho }=6.0$. Our result supports the idea of universality of neutral vector mesons and clarifies the role of accounting of $1/N_c$ corrections to its fulfilment.

The causal structure of the recent loop quantum gravity black hole collapse model [J. G. Kelly et al., Classical Quant. Grav. 38, 04LT01 (2021)] is analyzed. As the spacetime is only approximately diffeomorphism invariant up to powers of $\hslash$, it is not straightforwardly possible to find global conformally compactified coordinates or to construct the Penrose diagram. Therefore, radial ingoing and outgoing light rays are studied to extract the causal features and sketch a causal diagram. It was found that the eternal metric [J. G. Kelly et al., Phys. Rev. D 102, 106024 (2020)], which is the vacuum solution of the collapse model, has a causal horizon. However, in the collapsing case, light rays travel through matter to causally connect the regions inside and outside the horizon—the causal horizon is not present in the collapsing scenario. It is worked out that this is related to the shock wave and spacetime discontinuity, which allows matter traveling superluminally along a spacelike trajectory from the vacuum point of view, but remaining timelike from the matter perspective. The final causal diagram is a compact patch of a Reissner-Nordström causal diagram. Further, possibilities of a continuous matter collapse with only timelike evolution are studied. It is found that the time-reversed vacuum metric is also a solution of the dynamical equations, and a once continuously differentiable matching of the vacuum spacetime across the minimal radius is possible. This allows an everywhere continuous and timelike collapse process at the cost of an infinite extended causal diagram. This solution is part of an infinitely extended eternal black hole solution with a bounce, whose global extension is constructed. Due to the analysis of radial light rays, it is possible to sketch causal diagrams of these spacetimes.