We study the nonlinear spherical “top hat” collapse for Chaplygin and viscous unified cosmologies. The term unified refers to models where dark energy and dark matter are replaced by one single component. For the generalized Chaplygin gas (GCG), we extend previous results of R. A. A. Fernandes et al., [Phys. Rev. D 85, 083501 (2012)]. We discuss the differences at nonlinear level between the GCG with $\alpha =0$ and the $\mathrm{\Lambda }\mathrm{CDM}$ model. We show that both are indeed different. The bulk viscous model which differs from the GCG due to the existence of nonadiabatic perturbations is also studied. In this case, the clustering process is in general suppressed, and the viable parameter space of the viscous model that accelerates the background expansion does not lead to collapsed structures. This result challenges the viability of unified viscous models.

Dark energy might interact with cold dark matter in a direct, nongravitational way. However, the usual interacting dark energy models (with constant $w$) suffer from some catastrophic difficulties. For example, the $Q\propto {\rho }_{\mathrm{c}}$ model leads to an early-time large-scale instability, and the $Q\propto {\rho }_{\text{de}}$ model gives rise to the future unphysical result for cold dark matter density (in the case of a positive coupling). In order to overcome these fatal flaws, we propose in this paper an interacting dark energy model (with constant $w$) in which the interaction term is carefully designed to realize that $Q\propto {\rho }_{\text{de}}$ at the early times and $Q\propto {\rho }_{\mathrm{c}}$ in the future, simultaneously solving the early-time superhorizon instability and future unphysical ${\rho }_{\mathrm{c}}$ problems. The concrete form of the interaction term in this model is $Q=3\beta H\frac{{\rho }_{\mathrm{de}}{\rho }_{\mathrm{c}}}{{\rho }_{\mathrm{de}}+{\rho }_{\mathrm{c}}}$, where $\beta$ is the dimensionless coupling constant. We show that this model is actually equivalent to the decomposed new generalized Chaplygin gas (NGCG) model, with the relation $\beta =-\alpha w$. We calculate the cosmological perturbations in this model in a gauge-invariant way and show that the cosmological perturbations are stable during the whole expansion history provided that $\beta >0$. Furthermore, we use the Planck data in conjunction with other astrophysical data to place stringent constraints on this model (with eight parameters), and we find that indeed $\beta >0$ is supported by the joint constraint at more than $1\sigma$ level. The excellent theoretical features and the support from observations all indicate that the decomposed NGCG model deserves more attention and further investigation.

It has already been shown that in thermal nonlocal Nambu—Jona-Lasinio models some unphysical behavior, such as a negative pressure, may arise. In this paper, it is shown how this behavior can be related to the presence of highly unstable poles of the propagator of the model, for both the Gaussian and Lorentzian regulator cases. Computations are carried out within the real time formalism, which allows us to isolate the contributions from different poles and identify the source of these instabilities. It has also been shown in recent papers how these instabilities are softened by the inclusion of the Polyakov loop when a Gaussian regulator is considered. This paper shows how the softening of instabilities can be understood by studying the effect of the Polyakov loop on the poles of the propagator for the Gaussian regulator.

By employing the perturbative QCD (pQCD) factorization approach, we calculate the branching ratios and charge parity ($CP$)-violating asymmetries of the four ${\overline{B}}_s^0\to K\pi$ and $KK$ decays, with the inclusion of all known next-to-leading order (NLO) contributions. We find numerically that (a) the NLO contribution can interfere with the leading order (LO) part constructively or destructively for different decay modes; (b) the NLO contribution leads to a 22% decrease for the central values of the LO pQCD prediction for $\text{Br}({\overline{B}}_s^0\to K^{+}{\pi }^{-})$, but $\sim 50\%$ enhancement to the other three considered ${\overline{B}}_s$ decays, the agreement between the central values of the pQCD predictions and the data are therefore improved effectively after the inclusion of the NLO contributions; (c) for both ${\overline{B}}_s^0\to K^{+}{\pi }^{-}$ and ${\overline{B}}_s^0\to K^{+}{K}^{-}$ decays, the NLO pQCD predictions for the direct and mixing induced $CP$-violating asymmetries agree well with the measured values in both the sign and the magnitude; and (d) the theoretical errors of the pQCD predictions for decay rates are about 35% of the cental values and larger than that of the relevant data.

In light of the discovery of a standard model (SM)-like Higgs boson ($h$) at the LHC, we investigate the top quark to Higgs boson transition $t\to W^{*}bh$, which is the leading $t\to h$ decay mode in the SM. We find the decay branching fraction to be $1.80\times 10^{-9}$. In comparison, the two-body, loop-induced $t\to ch$ transition occurs at $\sim 10^{-14}$ in the SM. We consider the consequences of gauge-invariant dimension-six operators affecting the $t\overline{t}h$ interaction and find that the decay branching fraction may be increased by a factor of 2 within current constraints on the coupling parameters from collider experiments. We also extend the calculation to the $CP$-conserving Type I and Type II two-Higgs-doublet models, including both $CP$-even and $CP$-odd Higgs bosons. For neutral scalar masses at about 100 GeV, the decay rates can be several times larger than the SM result in the allowed range of model parameters. Observation prospects at present and future colliders are briefly addressed.

A triplet dark matter candidate from thermal leptogenesis is considered with building a model. The model is based on the standard two-Higgs-doublet model and seesaw mechanism with Higgs triplets. The parameters (couplings and masses) are adjusted for the observed small neutrino mass and the leptogenesis. Dark matter particles can annihilate and decay in this model. The time evolution of the dark matter number is governed by (co)annihilations in the expanding universe, and its mass is constrained by the observed relic density. The dark matter can decay into final states with three leptons (two charged leptons and one neutrino). We investigate whether the decay in a galaxy can account for cosmic ray anomalies in the positron and electron spectrum. A noticeable point is that if the dark matter decays into each lepton with different branching ratios, cosmic ray anomalies in AMS-02 measurements of the positron fraction and the Fermi LAT measurements of the electrons-plus-positrons flux could be simultaneously accounted for from its decay products.

We define a general class of superconformal inflationary attractor models [R. Kallosh et al., Phys. Rev. Lett. 112, 011303 (2014); J. High Energy Phys. 11 (2013) 198; A. Linde, arXiv:1402.0526, R. Kallosh, arXiv:1402.0527], which include, among others, inflationary models of “induced gravity” which were argued to retain perturbative unitarity up to the Planck scale [G. F. Giudice and H. M. Lee, arXiv:1402.2129]. The choice of the function $f(\varphi )$ in superconformal attractors for the models introduced by Giudice and Lee [arXiv:1402.2129] is $f(\varphi )={\varphi }^n-{\xi }^{-1}$. We present both superconformal and supergravity versions of these models, which were derived by Kallosh et al. [Phys. Rev. Lett. 112, 011303 (2014); J. High Energy Phys. 11 (2013) 198]; Linde [arXiv:1402.0526], Kallosh [arXiv:1402.0527] for arbitrary $f(\varphi )$, together with the universal conditions required for stabilization of the extra three moduli present in the superconformal attractors, in addition to the inflaton.

We discuss how to introduce Faddeev-Popov ghosts to the Keldysh-Schwinger formalism describing equilibrium and nonequilibrium statistical systems of quantum fields such as the quark-gluon plasma, which is considered. The plasma is assumed to be homogeneous in a coordinate space but the momentum distribution of plasma constituents is arbitrary. Using the technique of the generating functional, we derive the Slavnov-Taylor identities and one of them expresses the ghost Green’s function, which we look for, through the gluon one. As an application, the Green’s function of ghosts is used to compute the gluon polarization tensor in the hard loop approximation that appears to be automatically transverse, as required by the gauge invariance.

We define and investigate a quantization of null hypersurfaces in the context of loop quantum gravity on a fixed graph. The main tool we use is the parametrization of the theory in terms of twistors, which has already proved useful in discussing the interpretation of spin networks as the quantization of twisted geometries. The classical formalism can be extended in a natural way to null hypersurfaces, with the Euclidean polyhedra replaced by null polyhedra with spacelike faces, and SU(2) by the little group ISO(2). The main difference is that the simplicity constraints present in the formalism are all first class, and the symplectic reduction selects only the helicity subgroup of the little group. As a consequence, information on the shapes of the polyhedra is lost, and the result is a much simpler, Abelian geometric picture. It can be described by a Euclidean singular structure on the two-dimensional spacelike surface defined by a foliation of spacetime by null hypersurfaces. This geometric structure is naturally decomposed into a conformal metric and scale factors, forming locally conjugate pairs. Proper action-angle variables on the gauge-invariant phase space are described by the eigenvectors of the Laplacian of the dual graph. We also identify the variables of the phase space amenable to characterize the extrinsic geometry of the foliation. Finally, we quantize the phase space and its algebra using Dirac’s algorithm, obtaining a notion of spin networks for null hypersurfaces. Such spin networks are labeled by SO(2) quantum numbers and are embedded nontrivially in the unitary, infinite-dimensional irreducible representations of the Lorentz group.

In loop quantum gravity the quantum states of a black hole horizon consist of pointlike discrete quantum geometry excitations (or punctures) labeled by spin $j$. The excitations possibly carry other internal degrees of freedom, and the associated quantum states are eigenstates of the area $A$ operator. The appropriately scaled area operator $A/(8\pi \ell )$ can also be interpreted as the physical Hamiltonian associated with the quasilocal stationary observers located at a small distance $\ell$ from the horizon. Thus, the local energy is entirely accounted for by the geometric operator $A$. Assuming that: Close to the horizon the quantum state has a regular energy momentum tensor and hence the local temperature measured by stationary observers is the Unruh temperature. Degeneracy of matter states is exponential with the area $\exp (\lambda A/{\ell }_p^2)$, which is supported by the well-established results of QFT in curved spacetimes, which do not determine $\lambda$ but assert an exponential behavior. The geometric excitations of the horizon (punctures) are indistinguishable. And finally that the semiclassical limit the area of the black hole horizon is large in Planck units. It follows that: Up to quantum corrections, matter degrees of freedom saturate the holographic bound, viz., $\lambda$ must be equal to $\frac{1}{4}$. Up to quantum corrections, the statistical black hole entropy coincides with Bekenstein-Hawking entropy $S=A/(4{\ell }_p^2)$. The number of horizon punctures goes like $N\propto \sqrt{A/{\ell }_p^2}$; i.e., the number of punctures $N$ remains large in the semiclassical limit. Fluctuations of the horizon area are small $\mathrm{\Delta }A/A\propto {({\ell }_p^2/A)}^{1/4}$, while fluctuations of the area of an individual puncture are large (large spins dominate). A precise notion of local conformal invariance of the thermal state is recovered in the $A\to \infty$ limit where the near horizon geometry becomes Rindler. We also show how the present model (constructed from loop quantum gravity) provides a regularization of (and gives a concrete meaning to) the formal Gibbons-Hawking Euclidean path-integral treatment of the black hole system. These results offer a new scenario for semiclassical consistency of loop quantum gravity in the context of black hole physics, and suggest a concrete dynamical mechanism for large spin domination leading simultaneously to semiclassicality and continuity.

We compute quantum corrections to the Raychaudhuri equation by replacing classical geodesics with quantal (Bohmian) trajectories and show that they prevent focusing of geodesics and the formation of conjugate points. We discuss implications for the Hawking-Penrose singularity theorems and curvature singularities.

We estimate dark matter (DM) density for the Universe with a reheating temperature smaller than the mass of DM, assuming DM to be a weakly interacting massive particle. During the reheating process, an inflaton decays and releases high-energy particles, which are scattered inelastically by the thermal plasma and emit many particles. DMs are produced through these inelastic scattering processes and pair creation processes by high-energy particles. We properly take account of the Landau-Pomeranchuk-Migdal effect on inelastic processes and show that the resultant energy density of DM is much larger than that estimated in the literature and can be consistent with that observed when the mass of DM is larger than $O(100)\mathrm{GeV}$.

We examine the regime of validity of $N$-point spectra predictions of single-field inflation models that invoke transient periods of nonadiabatic evolution. Such models generate oscillatory features in these spectra spanning frequencies up to the inverse time scale of the transient feature. To avoid strong coupling of fluctuations in these theories this scale must be at least $\sim 10^{-2}/c_s$ of the Hubble time during inflation, where $c_s$ is the inflaton sound speed. We show that, in such models, the signal-to-noise ratio of the bispectrum is bounded from above by that of the power spectrum, implying that searches for features due to nonadiabatic evolution are best focused first on the latter.

We study the production of primordial black holes (PBHs) during the preheating stage that follows a chaotic inflationary phase. The scalar fields present in the process are evolved numerically using a modified version of the HLATTICE code. From the output of the numerical simulation, we compute the probability distribution of curvature fluctuations, paying particular attention to subhorizon scales. We find that in some specific models these modes grow to large amplitudes developing highly non-Gaussian probability distributions. We then calculate PBH abundances using the standard Press–Schechter criterion and find that overproduction of PBHs is likely in some regions of the chaotic preheating parameter space.

We study the semileptonic decays of $B^{-}\to f_0(1710,1500,1370)e^{-}{\overline{\nu }}_e$, in which the three $f_0$ states mix with glueball, $\overline{s}s$, and $(\overline{u}u+\overline{d}d)/\sqrt{2}$ states, respectively. By averaging the mixings fitted in the literature, we find that the branching ratios of $B^{-}\to f_0{e}^{-}{\overline{\nu }}_e$ are $O({10}^{-6})$, $O({10}^{-6})$, and $O({10}^{-5})$, respectively, which can be simultaneously observed in experiments at $B$ factories. The large predicted branching rate for $B^{-}\to f_0(1370)e^{-}{\overline{\nu }}_e$ would provide a clean mode to directly observe the $f_0(1370)$ state.

In connection with massless two-flavor QCD, we analyze the chiral symmetry restoring phase transition using three distinct gluon-quark vertices and two different assumptions about the long-range part of the quark-quark interaction. In each case, we solve the gap equation, locate the transition temperature $T_c$, and use the maximum entropy method to extract the dressed-quark spectral function at $T>T_c$. Our best estimate for the chiral transition temperature is $T_c=147\pm 8\mathrm{MeV}$, and the deconfinement transition is coincident. For temperatures markedly above $T_c$, we find a spectral density that is consistent with those produced using a hard thermal loop expansion, exhibiting both a normal and plasmino mode. On a domain $T\in [T_c,T_s]$, with $T_s\simeq 1.5T_c$, however, with each of the six kernels we considered, the spectral function contains a significant additional feature. Namely, it displays a third peak, associated with a zero mode, which is essentially nonperturbative in origin and dominates the spectral function at $T=T_c$. We suggest that the existence of this mode is a signal for the formation of a strongly coupled quark-gluon plasma and that this strongly interacting state of matter is likely a distinctive feature of the QCD phase transition.

We determine the curvature of the (pseudo)critical line of QCD with $n_f=2+1$ staggered fermions at nonzero temperature and quark density by analytic continuation from imaginary chemical potentials. Monte Carlo simulations are performed by adopting the highly improved staggered quarks /tree action discretization, as implemented in the code by the MILC Collaboration, suitably modified to include a nonzero imaginary baryon chemical potential. We work on a line of constant physics, as determined in Ref. [1], adjusting the couplings so as to keep the strange quark mass $m_s$ fixed at its physical value, with a light to strange mass ratio of $m_l/m_s=1/20$. In the present investigation, we set the chemical potential at the same value for the three quark species, ${\mu }_l={\mu }_s\equiv \mu$. We explore lattices of different spatial extensions, ${16}^3\times 6$ and ${24}^3\times 6$, to check for finite size effects, and present results on a ${32}^3\times 8$ lattice, to check for finite cutoff effects. We discuss our results for the curvature $\kappa$ of the (pseudo)critical line at $\mu =0$, which indicate $\kappa =0.018(4)$, and compare them with previous lattice determinations by alternative methods and with experimental determinations of the freeze-out curve.

The cross sections of the processes $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi$ and $K_S^0{K}_S^{0}J/\psi$ are measured via initial state radiation at center-of-mass energies between the threshold and 6.0 GeV using a data sample of $980{\mathrm{fb}}^{-1}$ collected with the Belle detector on or near the $\mathrm{{\rm Y}}(nS)$ resonances, where $n=1,2,\dots ,5$. The cross sections for $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi$ are at a few pb level and the average cross section for $e^{+}{e}^{-}\to K_S^0{K}_S^{0}J/\psi$ is $1.8\pm 0.6(\text{stat})\pm 0.3(\text{syst})\mathrm{pb}$ between 4.4 and 5.2 GeV. All of them are consistent with previously published results with improved precision. A search for resonant structures and associated intermediate states in the cross section of the process $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi$ is performed.

We present a new method to observe direct $CP$ violation in $D$ mesons using Bose symmetry and the Dalitz plot. We apply the method to processes such as $B\to D^0{\overline{D}}^{0}P$, where $P$ is either a $K$ or a $\pi$. By choosing to reconstruct $D$ mesons only through their decays into $CP$ eigenstates, we show that any asymmetry in the Dalitz plot can arise only through direct $CP$ violation. We further show how $CP$ violation parameters can be determined. Since the approach involves only Bose symmetry, the method is applicable to any multibody process that involves $D^0{\overline{D}}^0$ in the final state. We briefly discuss how $B\to D^{*}{\overline{D}}^{*}P$ can also be used in a similar way. This method can also be applied to $D^0{\overline{D}}^0$ in the final state from continuum $c\overline{c}$ production.