In the present work, we study the large scale matter power spectrum as well as the observed galaxy power spectrum for a noncanonical tachyon field dark energy model considering the full general relativistic perturbation equations. We form a set of coupled autonomous equations, including both the background and linearly perturbed quantities, and obtain their solutions numerically with proper set of initial conditions. We consider different scalar field potentials for our study. Deviations from the concordance $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model are studied for different relevant quantities. Our study shows that the noncanonical tachyon dark energy model produces enhanced gravitational potentials and comoving density contrast, as well as linear growth factor for matter perturbations compared to $\mathrm{\Lambda }\mathrm{CDM}$. It is also observed that, for tachyon dark energy models, there is suppression of power on large scales compared to both the $\mathrm{\Lambda }\mathrm{CDM}$ model as well as previously studied canonical scalar field models.

The correlation between the peak spectra energy ($E_p$) and the equivalent isotropic energy ($E_{\mathrm{iso}}$) of long gamma-ray bursts (GRBs), the so-called Amati relation, is often used to constrain the high-redshift Hubble diagram. Assuming Lambda cold dark matter cosmology, G.-J. Wang et al. [Astrophys. J. 836, 103 (2017)] found a $\gtrsim 3\sigma$ tension in the data-calibrated Amati coefficients between low and high redshift GRB samples. To reduce the impact of fiducial cosmology, we use the parametrization based on cosmic age (PAge), an almost model-independent framework to trace the cosmological expansion history. We find that the low and high redshift tension in Amati coefficients stays almost the same for the broad class of models covered by PAge, indicating that the cosmological assumption is not the dominant driver of the redshift evolution of GRB luminosity correlation. Next, we analyze the selection effect due to flux limits in observations. We find Amati relation evolves much more significantly across energy scales of $E_{\mathrm{iso}}$. We debias the GRB data by selectively discarding samples to match low-$z$ and high-$z$ $E_{\mathrm{iso}}$ distributions. After debiasing, the Amati coefficients agree well between low-$z$ and high-$z$ data groups, whereas the evidence of $E_{\mathrm{iso}}$ dependence of Amati relation remains to be strong. Thus, the redshift evolution of GRB luminosity correlation can be fully interpreted as a selection bias and does not imply cosmological evolution of GRBs.

A seemingly simple question, “how does warm inflation exit gracefully?”, has a more complex answer than in a cold paradigm. It has been highlighted here that whether warm inflation exits gracefully depends on three independent choices: The form of the potential, the choice of the warm inflation model (i.e., on the form of its dissipative coefficient) and the regime, of weak or strong dissipation, characterizing the warm inflation dynamics. Generic conditions on slow-roll parameters and several constraints on the different model parameters required for warm inflation to exit gracefully are derived.

It has been argued that supergravity models of inflation with vanishing sound speeds, $c_s$, lead to an unbounded growth in the production rate of gravitinos. We consider several models of inflation to delineate the conditions for which $c_s=0$. In models with unconstrained superfields, we argue that the mixing of the Goldstino and inflatino in a time-varying background prevents the uncontrolled production of the longitudinal modes. This conclusion is unchanged if there is a nilpotent field associated with supersymmetry breaking with constraint ${\mathbf{S}}^{\mathbf{2}}=0$, i.e., (s)Goldstino-less models. Models with a second orthogonal constraint, $\mathbf{S}(\mathbf{\Phi }-\overline{\mathbf{\Phi }})=0$, where $\mathbf{\Phi }$ is the inflaton superfield, which eliminates the inflatino, may suffer from the overproduction of gravitinos. However, we point out that these models may be problematic if this constraint originates from a UV Lagrangian, as this may require using higher derivative operators. These models may also exhibit other pathologies, such as $c_s>1$, which are absent in theories with the single constraint or unconstrained fields.

We present the cosmological analysis of the Gauss-Bonnet quasi-dilaton massive gravity theory. This offers a gravitational theory with a nonzero graviton mass. We calculate the complete set of background equations of motion. Also, we obtain the self-accelerating background solutions and we present the constraints on parameters to indicate the correct sign of parameters. In addition, we analyse tensor perturbations and calculate the mass of graviton and find the dispersion relation of gravitational waves for two cases. Finally, we investigate the propagation of gravitational perturbation in the Friedman-Lemaître-Robertson-Walker cosmology in the Gauss-Bonnet quasi-dilaton massive gravity.

We investigate the late-time evolution of the Universe within a cosmological model in which dark matter and dark energy are identified with two interacting scalar fields. Using methods of qualitative analysis of dynamical systems, we identify all cosmological solutions of this model. We show that viable solutions—in the sense that they correspond to a cosmic evolution in which a long enough matter-dominated era is followed by a current era of accelerated expansion—can be found in several regions of the parameter space. These solutions can be divided into two categories, namely, solutions that evolve to a state of everlasting accelerated expansion, in which the energy density of the dark-matter field rapidly approaches zero and the evolution becomes entirely dominated by the dark-energy field, and solutions in which the stage of accelerated expansion is temporary and the ratio between the energy densities of dark energy and dark matter tends, asymptotically, to a constant nonzero value.

We develop a scenario for the emergence of a nonsingular generic cosmological solution based on the WKB characterization of one of the two anisotropy degrees of freedom. We investigate the dynamics of the so-called inhomogeneous mixmaster in the “corner” configuration and inferring that one of the two anisotropic variables becomes small enough to explore the uncertainty principle. Then, we apply a standard WKB approximation to the dynamics of the Universe which has macroscopic volume, one macroscopic anisotropy and one microscopic quantum degree of freedom. Our study demonstrates the possibility that the Universe acquires a nonsingular classical behavior, retaining the quantum degree of freedom as a small oscillating ripple on a stationary Universe. The role of the so-called fragmentation process is also taken into account in outlining the generality of such a behavior in independent local space regions.

We study the merger rate of primordial black holes (PBHs) in the ellipsoidal-collapse model of halo to explain the dark matter abundance by the PBH merger estimated from the gravitational waves detections via the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) detectors. We indicate that the PBH merger rate within each halo for the ellipsoidal models is more significant than for the spherical models. We specify that the PBH merger rate per unit time and per unit volume for the ellipsoidal-collapse halo models is about one order of magnitude higher than the corresponding spherical models. Moreover, we calculate the evolution of the PBH total merger rate as a function of redshift. The results indicate that the evolution for the ellipsoidal halo models is more sensitive than spherical halo models, as expected from the models. Finally, we present a constraint on the PBH abundance within the context of ellipsoidal and spherical models. By comparing the results with the aLIGO mergers during the third observing run, we show that the merger rate in the ellipsoidal-collapse halo models falls within the aLIGO window, while the same result is not valid for the spherical-collapse ones. Furthermore, we compare the total merger rate of PBHs in terms of their fraction in the ellipsoidal-collapse halo models for several masses of PBHs. The results suggest that the total merger rate of PBHs changes inversely with their masses. We also estimate the relation between the fraction of PBHs and their masses in the ellipsoidal-collapse halo model and show it for a narrow mass distribution of PBHs. The outcome shows that the constraint inferred from the PBH merger rate for the ellipsoidal-collapse halo models can be potentially stronger than the corresponding result obtained for the spherical-collapse ones.

Two-particle momentum correlations of $N$ identical bosons are studied in the quantum canonical ensemble. We define the latter as a properly selected subensemble of events associated with the grand canonical ensemble which is characterized by a constant temperature and a harmonic-trap chemical potential. The merits of this toy model are that it can be solved exactly, and that it demonstrates some interesting features revealed recently in small systems created in $p+p$ collisions at the LHC. We find that partial coherence can be observed in particle emission from completely thermal ensembles of events if instead of inclusive measurements one studies the two-boson distribution functions related to the events with particle numbers selected in some fixed multiplicity bins. The corresponding coherence effects increase with the multiplicity.

Universal extra dimension (UED) is a well-motivated and well-studied scenario. One of the main motivations is the presence of a dark matter (DM) candidate, namely the lightest level-one Kaluza-Klein particle, in the particle spectrum of UED. The minimal version of UED (mUED) scenario is highly predictive with only two parameters, namely the radius of compactification and cutoff scale, to determine the phenomenology. Therefore, stringent constraint results from the WMAP/PLANCK measurement of DM relic density (RD) of the Universe. The production and decays of level-one quarks and gluons in UED scenarios give rise to multijet final states at the Large Hadron Collider (LHC) experiment. We study the ATLAS search for multijet plus missing transverse energy signatures at the LHC with 13 TeV center-of-mass energy and 139 inverse femtobarn integrated luminosity. In view of the fact that the DM RD allowed part of mUED parameter space has already been ruled out by the ATLAS multijet search, we move on to a less restricted version of UED, namely the nonminimal UED (nmUED), with nonvanishing boundary-localized terms (BLTs). The presence of BLTs significantly alters the dark matter as well as the collider phenomenology of nmUED. We obtain stringent bounds on the BLT parameters from the ATLAS multijet plus missing transverse energy search.

We study the emergence of de Sitter space in Euclidean dynamical triangulations (EDT). Working within the semi-classical approximation, it is possible to relate the lattice parameters entering the simulations to the partition function of Euclidean quantum gravity. We verify that the EDT geometries behave semiclassically, and by making contact with the Hawking-Moss instanton solution for the Euclidean partition function, we show how to extract a value of the renormalized Newton’s constant from the simulations. This value is consistent with that of our previous determination coming from the interaction of scalar particles. That the same universal constant appears in these two different sectors of the theory is a strong indication that EDT provides a viable formulation of quantum gravity.

We present a lattice QCD calculation of the axial $\gamma W$-box diagrams relevant for the kaon semileptonic decays. We utilize a recently proposed method, which connects the electroweak radiative corrections in Sirlin’s representation to that in chiral perturbation theory. It allows us to use the axial $\gamma W$-box correction in the SU(3) limit to obtain the low energy constants for chiral perturbation theory. From first principles our results confirm the previously used low energy constants provided by the minimal resonance model with a significant reduction in uncertainties.

Statistical modeling is a key component in the extraction of physical results from lattice field theory calculations. Although the general models used are often strongly motivated by physics, many model variations can frequently be considered for the same lattice data. Model averaging, which amounts to a probability-weighted average over all model variations, can incorporate systematic errors associated with model choice without being overly conservative. We discuss the framework of model averaging from the perspective of Bayesian statistics, and give useful formulas and approximations for the particular case of least-squares fitting, commonly used in modeling lattice results. In addition, we frame the common problem of data subset selection (e.g., choice of minimum and maximum time separation for fitting a two-point correlation function), as a model selection problem and study model averaging as a straightforward alternative to manual selection of fit ranges. Numerical examples involving both mock and real lattice data are given.

We investigate the process of ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }D\overline{D}$, by taking into account the contributions from the $s$-wave $D\overline{D}$ interaction within the coupled-channel unitary approach, and the intermediate $\psi (3770)$ resonance. In addition to the peak of the $\psi (3770)$, an enhancement near the $D\overline{D}$ mass threshold is found in the $D\overline{D}$ invariant mass distributions, which should be the reflection of the $D\overline{D}$ bound state. We encourage our experimental colleagues to measure the $D\overline{D}$ invariant mass distribution of the ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }D\overline{D}$ process, which is crucial to search for the $D\overline{D}$ bound state and to understand the heavy-hadron heavy-hadron interactions.

We consider the hadroproduction of a massive charged lepton plus the corresponding neutrino through the Drell-Yan mechanism. We present a new computation of the mixed QCD-electroweak (EW) corrections to this process. The cancellation of soft and collinear singularities is achieved by using a formulation of the $q_T$ subtraction formalism derived from the next-to-next-to-leading-order QCD calculation for heavy-quark production. For the first time, all the real and virtual contributions due to initial- and final-state radiation are consistently included without any approximation, except for the finite part of the two-loop virtual correction, which is computed in the pole approximation and suitably improved through a reweighting procedure. We demonstrate that our calculation is reliable in both on-shell and off-shell regions, thereby providing the first prediction of the mixed QCD-EW corrections in the entire region of the lepton transverse momentum. The computed corrections are in qualitative agreement with what we obtain in a factorized approach of QCD and EW corrections. At large values of the lepton $p_T$, the mixed QCD-EW corrections are negative and increase in size, to about $-20\%$ with respect to the next-to-leading-order QCD result at $p_T=500\mathrm{GeV}$.

We investigate the transverse target spin asymmetry $A_{UT}^{\sin {\varphi }_S}$ for the unpolarized $\mathrm{\Lambda }$ production in semi-inclusive deep inelastic scattering (SIDIS) with the transverse momentum of the final-state lambda hyperon being integrated out. The asymmetry is contributed by the product of the transversity distribution function $h_1(x)$ of the nucleon and the collinear twist-3 fragmentation function $\tilde{H}(z)$ of the $\mathrm{\Lambda }$ hyperon. The later one originates from the quark-gluon-quark correlation and is a naive time-reversal-odd function. We calculate $\tilde{H}$ of the $\mathrm{\Lambda }$ hyperon by adopting a diquark spectator model. Using the numerical result of $\tilde{H}(z)$ and the available parametrization of $h_1(x)$ from SIDIS data, we predict the $\sin {\varphi }_S$ asymmetry in the electroproduction of the $\mathrm{\Lambda }$ hyperon in the kinematical region of Electron-Ion Collider (EIC), EIC in China (EicC), and COMPASS. In the phenomenological analysis, we include the evolution effect of the distribution functions and the fragmentation functions. The results show that the asymmetries for the $\mathrm{\Lambda }$ production SIDIS process are around 0.1 and may be accessible at EIC, EicC, and COMPASS. We also find that the evolution of fragmentation function can affect the size of asymmetry.

We provide high-precision predictions for muon-pair and tau-pair productions in a photon-photon collision by considering a complete set of one-loop-level scattering amplitudes, i.e., electroweak (EW) corrections together with soft and hard QED radiation. Accordingly, we present a detailed numerical discussion with particular emphasis on the pure QED corrections as well as genuinely weak corrections. The effects of angular and initial beam polarization distributions on production rates are also discussed. An improvement is observed by a factor of two with oppositely polarized photons. Our results indicate that the one-loop EW radiative corrections enhance the Born cross section and the total relative correction is typically about 10% for both production channels. It appears that the full EW corrections to $\gamma \gamma \to {\ell }^{-}{\ell }^{+}$ are required to match a percent level accuracy.

We report measurements of the branching fractions and $CP$ asymmetries for $D_s^{+}\to K^{+}\eta$, $D_s^{+}\to K^{+}{\pi }^0$, and $D_s^{+}\to {\pi }^{+}\eta$ decays, and the branching fraction for $D_s^{+}\to {\pi }^{+}{\pi }^0$. Our results are based on a data sample corresponding to an integrated luminosity of $921{\mathrm{fb}}^{-1}$ collected by the Belle detector at the KEKB $e^{+}{e}^{-}$ asymmetric-energy collider. Our measurements of $CP$ asymmetries in these decays are the most precise to date; no evidence for $CP$ violation is found.

Based on $4.481\times {10}^8\psi (3686)$ events collected with the BESIII detector at BEPCII, the branching fraction of the isospin violating decay $\psi (3686)\to {\overline{\mathrm{\Sigma }}}^0\mathrm{\Lambda }+\mathrm{c}.\mathrm{c}.$ is measured to be $(1.60\pm 0.31\pm 0.13\pm 0.58)\times {10}^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is the uncertainty arising from interference with the continuum. This result is significantly smaller than the measurement based on CLEO-c data sets. The decays ${\chi }_{cJ}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ are measured via $\psi (3686)\to \gamma {\chi }_{cJ}$, and the branching fractions are determined to be $\mathcal{B}({\chi }_{c0}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }})=(3.64\pm 0.10\pm 0.10\pm 0.07)\times {10}^{-4}$, $\mathcal{B}({\chi }_{c1}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }})=(1.31\pm 0.06\pm 0.06\pm 0.03)\times {10}^{-4}$, $\mathcal{B}({\chi }_{c2}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }})=(1.91\pm 0.08\pm 0.17\pm 0.04)\times {10}^{-4}$, where the third uncertainties are systematic due to the $\psi (3686)\to \gamma {\chi }_{cJ}$ branching fractions.

We present a formalism that resums both soft-virtual (SV) and next-to-SV (NSV) contributions to all orders in perturbative QCD for the rapidity distribution of any colorless particle produced in hadron colliders. Using state-of-the-art results, we determine the complete NSV contributions to third order in the strong coupling constant for the rapidity distributions for Drell-Yan and for Higgs boson in gluon fusion as well as bottom quark annihilation. Using our all-order $z$-space result, we show how the NSV contributions can be resummed in two-dimensional Mellin space.