In this work, we develop a universal picture from topology in the thermodynamic parameters space to describe first order phase transitions of black holes. By employing an off-shell internal energy, we find two types of topological defects. The first is normal, describing black holes which move with a nonzero velocity and acceleration, in a central force field. The second type of defects are exotic: they are static in the space, not describing black holes but encoding information about first order transitions. For each defect, we assign a winding number and an inertial mass. By studying neutral and charged black holes in asymptotically anti–de Sitter space, we show that first order transitions can be viewed as a once or twice interchange of winding numbers between black holes and the exotic defects, through wired action at a distance. This corresponds to the usual notion: a smaller black hole grows into a larger black hole or vice versa. However, our topological analysis illustrates that the transition can also be locally interpreted as virtual collisions between black holes and the exotic defects. In this interpretation, a smaller black hole first grows into a new exotic defect whereas an original exotic defect grows into a larger black hole. All the defects simply change their positions and momentums, rather than interchanging the winding numbers. The critical point of the transition can be extracted when all the defects meet in the parameters space. Certain quantities, such as the Jacobians and the velocities of normal defects show universal behaviors near the critical point.

We derive the equations of state of Fermi gas by maximizing the Fermi-Dirac entropy in modified gravity in the relativistic and nonrelativistic case. It will be demonstrated that the microphysics must depend on a given theory of gravity in order to consistently describe a physical system at a statistical equilibrium state.

We discuss the question of whether or not inflationary spacetimes can be geodesically complete in the infinite past. Geodesic completeness is a necessary condition for averting an initial singularity during eternal inflation. It is frequently argued that cosmological models which are expanding sufficiently fast (having average Hubble expansion rate $H_{\mathrm{avg}}>0$) must be incomplete in null and timelike past directions. This well-known conjecture relies on specific bounds on the integral of the Hubble parameter over a past-directed timelike or null geodesic. As stated, we show this claim is an open issue. We show that the calculation of $H_{\mathrm{avg}}$ yields a continuum of results for a given spacetime predicated upon the underlying topological assumptions. We present an improved definition for $H_{\mathrm{avg}}$ and introduce an uncountably infinite cohort of cosmological solutions which are geodesically complete despite having $H_{\mathrm{avg}}>0$. We discuss a standardized definition for inflationary spacetimes as well as quantum (semiclassical) cosmological concerns over physically reasonable scale factors.

The gravitational wave memory effect is a prediction of general relativity. The presence of memory effect in gravitational wave signals not only provides the chance to test an important aspect of general relativity, but also represents a potentially non-negligible contribution to the waveform for certain gravitational wave events. In this paper, we study the prospect of detecting the gravitational wave memory effect directly with the planned space-based gravitational wave detector—TianQin. We find that during its five years of operation, for the gravitational wave signals that could be detected by TianQin, about 0.5–2.0 signals may contain displacement memory effect with signal-to-noise ratios (SNRs) greater than 3. This suggests that the chance for TianQin to detect the displacement memory effect directly is low but not fully negligible. In contrast, the chance to detect the spin memory is negligible. We also study that in which parameter space, the memory effect is expected to be significant in waveform modeling.

Motivated by the fact that cosmological models based on $f(Q)$ gravity are very efficient in fitting observational datasets at both background and perturbation levels, we perform a combined dynamical system analysis of both background and perturbation equations in order to examine the validity of this result through an independent method. We examine two studied $f(Q)$ models of the literature, namely, the power-law and the exponential ones. For both cases, we obtain a matter-dominated saddle point characterized by the correct growth rate of matter perturbations, followed by the transition to a stable dark-energy-dominated accelerated universe in which matter perturbations remain constant. Furthermore, analyzing the behavior of $f{\sigma }_8$, we find that the models fit observational data successfully, obtaining a behavior similar to that of the Lambda cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) scenario, although the exponential model does not possess the latter as a particular limit. Hence, through the independent approach of dynamical systems, we do verify the results of observational confrontation, namely, that $f(Q)$ gravity can be considered as a very promising alternative to the $\mathrm{\Lambda }\mathrm{CDM}$ concordance model.

We present the effective-field theory (EFT-)based cosmological full-shape analysis of the anisotropic power spectrum of eBOSS quasars at the effective redshift $z_{\mathrm{eff}}=1.48$. We perform extensive tests of our pipeline on simulations, paying particular attention to the modeling of observational systematics, such as redshift smearing, fiber collisions, and the radial integral constraint. Assuming the minimal $\mathrm{\Lambda }$ cold dark matter model, and fixing the primordial power spectrum tilt and the physical baryon density, we find the Hubble constant $H_0=(66.7\pm 3.2)\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, the matter density fraction ${\mathrm{\Omega }}_m=0.32\pm 0.03$, and the late-time mass fluctuation amplitude ${\sigma }_8=0.95\pm 0.08$. These measurements are fully consistent with the Planck cosmic microwave background results. Our eBOSS quasar $S_8$ posterior, $0.98\pm 0.11$, does not exhibit the so-called $S_8$ tension. Our work paves the way for systematic full-shape analyses of quasar samples from future surveys like DESI.

We resolve the potential-restriction problem in K/G inflation by introducing nonminimal coupling. In this context, Higgs field successfully drives inflation satisfying cosmic microwave background (CMB) observations while enhancing curvature perturbations at small scales, which in turn accounts for primordial black holes (PBHs) and scalar induced gravitational waves (SIGWs). We then uncover the effect of the noncanonical kinetic coupling function in more detail and study its the observational constraint. Besides, we also give the gauge invariant expression for the integral kernel of SIGWs, which is related to terms propagating with the speed of light. Finally, the non-Gaussian effect on PBH abundance and SIGWs is studied. We find that non-Gaussianity makes PBHs form more easily, but its effect on the energy density of SIGWs is negligible.

We provide a systematic study of the position-dependent correlation function in weak-lensing convergence maps and its relation to the squeezed limit of the three-point correlation function (3PCF) using state-of-the-art numerical simulations. We relate the position-dependent correlation function to its harmonic counterpart, i.e., the position-dependent power spectrum or equivalently the integrated bispectrum (IB). We use a recently proposed improved fitting function, BiHalofit, for the bispectrum to compute the theoretical predictions as a function of source redshifts. In addition to low redshift results ($z_s=1.0–2.0$) we also provide results for maps inferred from lensing of the cosmic microwave background (CMB), i.e., $z_s=1100$. We include a Euclid-type realistic survey mask and noise. In agreement with the recent studies on the position-dependent power spectrum, we find that the results from simulations are consistent with the theoretical expectations when appropriate corrections are included. Performing a rough estimate, we find that the signal-to-noise (S/N) for the detection of position-dependent correlation function from Euclid-type mask with $f_{\mathrm{sky}}=0.35$, can range between 6–12 depending on the value of the intrinsic ellipticity distribution parameter ${\sigma }_{\epsilon }=0.3–1.0$. For reconstructed $\kappa$ maps using an ideal CMB survey the $\mathrm{S}/\mathrm{N}\approx 1.8$. We also found that a 10% deviation in ${\sigma }_8$ can be detected using IB for the optimistic case of ${\sigma }_{\epsilon }=0.3$ with a $\mathrm{S}/\mathrm{N}\approx 5$. The S/N for such detection in case of ${\mathrm{\Omega }}_M$ is lower.

A perturbation on the background inflaton potential can lead inflation into the ultraslow-roll stage and can thus remarkably enhance the power spectrum ${\mathcal{P}}_{\mathcal{R}}(k)$ of the primordial curvature perturbation on small scales. Such an enhanced ${\mathcal{P}}_{\mathcal{R}}(k)$ will result in primordial black holes (PBHs), contributing a significant fraction of dark matter, and will simultaneously generate sizable scalar-induced gravitational waves (SIGWs) as a second-order effect. In this work, we calculate the PBH abundances $f_{\mathrm{PBH}}(M)$ and SIGW spectra ${\mathrm{\Omega }}_{\mathrm{GW}}(f)$ in peak theory. We obtain the PBHs with desirable abundances in one or two typical mass windows at ${10}^{-17}{M}_{\odot }$, ${10}^{-13}{M}_{\odot }$, and $30M_{\odot }$, respectively. At the same time, the relevant SIGWs are expected to be observed by the next-generation gravitational wave detectors, without spoiling the current constraint. Especially, the SIGW associated with the PBH of $30M_{\odot }$ can also interpret the potential isotropic stochastic gravitational wave background from the NANOGrav 12.5-year dataset.

We analyze the phase transition in improved holographic QCD to obtain an estimate of the gravitational wave signal emitted in the confinement transition of a pure SU(3) Yang-Mills dark sector. We derive the effective action from holography and show that the energy budget and duration of the phase transition can be calculated with minor errors. These are used as input to obtain a prediction of the gravitational wave signal. To our knowledge, this is the first computation of the gravitational wave signal in a holographic model designated to match lattice data on the thermal properties of pure Yang-Mills.

We apply Low’s theorem to soft gluon emission from heavy quark scattering in the nonperturbative strongly interacting quark-gluon plasma (sQGP). The sQGP is described in terms of the dynamical quasiparticles and adjusted to reproduce the EoS from lattice QCD at finite temperature and chemical potential. Since the emitted gluon is soft and of long wavelength, it does not provide information on the detailed structure of the scattering, and only the emission from incoming and outgoing partons is enough. It simplifies the calculations making the scattering amplitude factorizable into the elastic scattering and the emission of soft gluon. Imposing a proper upper limit on the emitted gluon energy, we obtain the gauge-invariant scattering cross sections of heavy quarks with the massive partons of the medium as well as their transport coefficients (momentum drag and diffusion) in the QGP and compare with those from the elastic scattering without gluon emission.

In this paper we carry out a systematic texture study of the neutrino mass matrix with the Ansätze—(i) one vanishing minor and (ii) the zero sum of the mass eigenvalues with the $CP$ phases (henceforth vanishing trace). There are six possible textures of a neutrino mass matrix with one vanishing minor. The viability of each texture is checked with $3\sigma$ values of current neutrino data by drawing scatter plots. In our analysis we are motivated to use the ratio of solar to atmospheric mass-squared differences $R_{\nu }$ for its precise measurement (and also the atmospheric mixing angle ${\theta }_{23}$) to constrain phenomenologically first the Dirac $CP$ phase $\delta$ in the range of 0°–360° for a given texture with the solutions of the constraint equations. Subsequently we employ this constrained $\delta$ to determine the range of completely unknown Majorana $CP$ phases ($\alpha$ and $\beta$) for all the viable textures. We also check the neutrinoless double beta decay rate $|m_{ee}|$ and the Jarlskog invariant $J_{cp}$ for the textures. Finally the symmetry realization of all the viable textures under the flavor symmetry group $Z_5$ via seesaw mechanism is implemented along with the FN mechanism to determine mass hierarchy structure.

A final state consisting of one charged lepton, at least one jet, and little missing transverse energy can be a very promising signature of new physics at the LHC across a wide range of models. However, it has received only limited attention so far. In this work we discuss the potential sensitivity of this channel to various new physics scenarios. To demonstrate our point, we consider its application to lepton parton distribution functions (PDFs) at the LHC in the context of supersymmetry. These lepton PDFs can lead to resonant squark production (similar to leptoquarks) via lepton number violating couplings present in $R$-parity violating supersymmetry (RPV-SUSY). Unlike leptoquarks, in RPV-SUSY there are many possible decay modes leading to a wide range of signatures. We propose two generic search regions: (a) a single first or second generation charged lepton, exactly 1 jet and low missing transverse energy, and (b) a single first or second generation charged lepton, at least 3 jets, and low missing transverse energy. We demonstrate that together these cover a large range of RPV-SUSY signatures, and have the potential to perform better than existing low-energy bounds, while being general enough to extend to a wide range of possible models hitherto not explored at the LHC.

The ${\gamma }^{\star }{\gamma }^{\star }\to \pi \pi$ scattering amplitude plays a key role in a wide range of phenomena, including understanding the inner structure of scalar resonances as well as constraining the hadronic contributions to the anomalous magnetic moment of the muon. In this work, we explain how the infinite-volume Minkowski amplitude can be constrained from finite-volume Euclidean correlation functions. The relationship between the finite-volume Euclidean correlation functions and the desired amplitude holds up to energies where $3\pi$ states can go on shell, and is exact up to exponentially small corrections that scale like $\mathcal{O}(e^{-m_{\pi }L})$, where $L$ is the spatial extent of the cubic volume and $m_{\pi }$ is the pion mass. In order to implement this formalism and remove all power-law finite volume errors, it is necessary to first obtain $\pi \pi \to \pi \pi$, $\pi {\gamma }^{\star }\to \pi$, ${\gamma }^{\star }\to \pi \pi$, and $\pi \pi {\gamma }^{\star }\to \pi \pi$ amplitudes; all of which can be determined via lattice quantum chromodynamic calculations.

One possible interpretation of two narrow ${\mathrm{\Omega }}_c^0$ states reported by the LHCb Collaboration at CERN in 2017 is that they are pentaquarks belonging to a $\overline{\mathbf{15}}$ exotic SU(3) representation, as predicted by the chiral quark-soliton model. If so, there must exist a number of other exotic states since the model predicts three different $\overline{\mathbf{15}}$ multiplets of heavy baryons. We show that, depending on the soliton spin $J$, these states are either very narrow or very broad. This explains why they might have escaped experimental observation. Furthermore, we show that the lightest members of these multiplets are stable against two body strong decays.

We study the double-gluon hybrid states with the quark-gluon contents $\overline{q}qgg$ ($q=u/d$) and $\overline{s}sgg$. We construct twelve double-gluon hybrid currents with various quantum numbers, five of which are found to be zero due to some internal symmetries between the two gluon fields. We use the remaining seven currents to perform QCD sum rule analyses. Especially, the masses of the double-gluon hybrid states with the exotic quantum number $J^{PC}=2^{+-}$ are calculated to be $M_{|\overline{q}qgg;2^{+-}⟩}=2.26_{-0.25}^{+0.20}\mathrm{GeV}$ and $M_{|\overline{s}sgg;2^{+-}⟩}=2.38_{-0.25}^{+0.19}\mathrm{GeV}$. Their two- and three-meson decay patterns are also investigated.

In this work we study the doubly charmed baryon decays ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}_c^{(\prime )+}{\pi }^{+}$ within the framework of the nonrelativistic quark model (NRQM). Factorizable amplitudes are expressed in terms of transition form factors, while nonfactorizable amplitudes arising from the inner $W$ emission are evaluated using current algebra and the pole model and expressed in terms of baryonic matrix elements and axial-vector form factors. Nonperturbative parameters are then calculated using the NRQM. They can be expressed in terms of the momentum integrals of baryon wave functions, which are in turn expressed in terms of the harmonic oscillator parameters ${\alpha }_{\rho }$ and ${\alpha }_{\lambda }$ for $\rho$- and $\lambda$-mode excitation. The measured ratio $R$ of the branching fraction of ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}_c^{\prime +}{\pi }^{+}$ relative to ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}_c^{+}{\pi }^{+}$ can be accommodated in the NRQM with ${\alpha }_{\rho 1}$ and ${\alpha }_{{\rho }_2}$ being in the vicinity of 0.51 and 0.19, respectively, where ${\alpha }_{\rho 1}$ is the ${\alpha }_{\rho }$ parameter for ${\mathrm{\Xi }}_{cc}^{++}$ and ${\alpha }_{\rho 2}$ for ${\mathrm{\Xi }}_c^{(\prime )+}$. Decay asymmetries are predicted to be $-0.78$ and $-0.89$ for ${\mathrm{\Xi }}_c^{+}{\pi }^{+}$ and ${\mathrm{\Xi }}_c^{\prime +}{\pi }^{+}$ modes, respectively, which can be tested in the near future. We compare our results with other works and point out that although some other models can accommodate the ratio $R$, they tend to lead to a branching fraction of ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}_c^{+}{\pi }^{+}$ too large compared to that inferred from the LHCb measurement of its rate relative to ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Lambda }}_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}$.

Using $e^{+}{e}^{-}$ annihilation data corresponding to an integrated luminosity of $2.93{\mathrm{fb}}^{-1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the branching fractions of the inclusive decays $D^0\to {\pi }^{+}{\pi }^{+}{\pi }^{-}X$ and $D^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}X$, where pions from $K_S^0$ decays have been excluded from the ${\pi }^{+}{\pi }^{+}{\pi }^{-}$ system and $X$ denotes any possible particle combination. The branching fractions of $D^0(D^{+})\to {\pi }^{+}{\pi }^{+}{\pi }^{-}X$ are determined to be $\mathcal{B}(D^0\to {\pi }^{+}{\pi }^{+}{\pi }^{-}X)=(17.60\pm 0.11\pm 0.22)\%$ and $\mathcal{B}(D^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}X)=(15.25\pm 0.09\pm 0.18)\%$, where the first uncertainties are statistical and the second systematic.

We consider a perturbative Gauss-Bonnet term supplementing the Einstein-Hilbert action and evaluate its effect on the spectrum of the scalar mode that triggers the Gregory-Laflamme instability of black strings in five-dimensional general relativity. After studying some properties of the static black string, we provide the correction to the Lichnerowicz operator up to $\mathcal{O}({\alpha }^2)$. For the scalar mode of the gravitational perturbation, we find a master variable and study its spectrum, providing an analysis of the regime of validity of our scheme. We show that the instability persists under the inclusion of the $R^2$ correction and that the critical wavelength increases with the value of $\alpha /r_{+}^2\ll 1$. We also construct the boosted black strings and compute the correction to the mass, the momentum, and the tension due to the higher curvature term. The presence of the dimensionful coupling $\alpha$ spoils the validity of the Smarr relation, which is the gravitational version of the Euler relation that must hold for every homogeneous, thermodynamic system. We show that this identity can be restored by working in an extended thermodynamic setup that includes variations of the Gauss-Bonnet coupling.

We present a new mechanism for cosmic acceleration consisting of a scalar field coupled to a triplet of classical U(1) gauge fields. The gauge fields are arranged in a homogeneous, isotropic configuration, with both electric- and magneticlike vacuum expectation values. The gauge fields provide a masslike term via a Chern-Simons interaction that suspends the scalar away from its potential minimum, thereby enabling potential-dominated evolution. We show this mechanism can drive a brief period of acceleration, such as dark energy, without the need for fine-tunings. We obtain simple analytic results for the dark energy equation of state and dependence on model parameters. In this model, the presence of the gauge field generically leads to a suppression of long-wavelength gravitational waves, with implications for the experimental search for cosmic microwave background B modes and direct detection of a stochastic gravitational wave background.