An antenna shower is a parton shower in which the basic move is a color-coherent $2\to 3$ parton splitting process. In this paper, we give compact forms for the spin-dependent antenna splitting functions involving massive partons of spin 0 and spin $1/2$.

In this work, we predict two charged charmoniumlike enhancement structures close to the $D^{*}\overline{D}$ and $D^{*}{\overline{D}}^{*}$ thresholds, where the Initial Single Pion Emission mechanism is introduced in the hidden-charm dipion decays of higher charmonia $\psi (4040)$, $\psi (4160)$, $\psi (4415)$ and charmoniumlike state $Y(4260)$. We suggest BESIII to search for these structures in the $J/\psi {\pi }^{+}$, $\psi (2S){\pi }^{+}$ and $h_b(1P){\pi }^{+}$ invariant mass spectra of the $\psi (4040)$ decays into $J/\psi {\pi }^{+}{\pi }^{-}$, $\psi (2S){\pi }^{+}{\pi }^{-}$ and $h_b(1P){\pi }^{+}{\pi }^{-}$. In addition, the experimental search for these enhancement structures in the $J/\psi {\pi }^{+}$, $\psi (2S){\pi }^{+}$ and $h_c(1P){\pi }^{+}$ invariant mass spectra of the $\psi (4260)$ hidden-charm dipion decays will be accessible at Belle and BABAR.

The implications of the fourth-generation quarks in the $B\to K_1(1270,1400){\ell }^{+}{\ell }^{-}$ with $\ell =\mu$, $\tau$ decays are studied, where the mass eigenstates $K_1(1270)$ and $K_1(1400)$ are the mixture of ${}^{1}P_1$ and ${}^{3}P_1$ states with the mixing angle ${\theta }_K$. In this context, we have studied various observables like branching ratio ($\mathcal{B}\mathcal{R}$), forward-backward asymmetry (${\mathcal{A}}_{FB}$) and longitudinal and transverse helicity fractions ($f_{L,T}$) of $K_1$ meson in $B\to K_1{\ell }^{+}{\ell }^{-}$ decays. To study these observables, we have used the light-cone QCD sum rules form factors and set the mixing angle ${\theta }_K=-34°$. It is noticed that the $\mathcal{B}\mathcal{R}$ is suppressed for $K_1(1400)$ as a final state meson compared to that of $K_1(1270)$. Same is the case when the final state leptons are tauons rather than muons. In both the situations, all the above mentioned observables are quite sensitive to the fourth-generation effects. Hence the measurements of these observables at LHC, for the above mentioned processes can serve as a good tool to investigate the indirect searches for the existence of fourth-generation quarks.

We study the creation of a black hole (BH) pair separated by a domain wall, in the presence of a cosmological constant. We construct the solution representing a BH pair with a domain wall and compute the Euclidean action to evaluate the probability of the pair creation in the background with a preexisting domain wall. The BHs can be either neutral or magnetically charged ones. We compare the results of the charged case with those of the neutral case with the same cosmological constant. We find that the production rate of a charged BH pair is always suppressed in comparison with that of the neutral one in both four and five dimensions, irrespective of the sign of the cosmological constant. The Euclidean action is equal to the minus of the entropy. Since the horizon area of a BH is decreased as the magnitude of its charge is increased in general, the decreasing creation rate can be understood in terms of the increasing charge. We obtain the explicit confirmation on the relation between the pair creation rate of the charged BHs and the area of horizons in both the four- and five-dimensional cases in the presence of a cosmological constant. The singularity of the domain wall universe with charged BHs, as distinct from that with neutral BHs, can be avoided.

We present a model-independent prescription for computing the gluon fusion production rate of a composite Higgs boson, which arises as a pseudo-Nambu-Goldstone boson, using effective Lagrangians. The calculation incorporates three different effects due to the composite nature of the Higgs, some of which were neglected previously. We apply the prescription to models with and without the collective breaking mechanism. In sharp contrast with the case of a fundamental Higgs scalar, the rate only depends on the decay constant $f$ and is not sensitive to masses of new particles. After including electroweak constraints, there is a substantial reduction in the rate, in the range of 10%–30% or greater.

We investigate the 2-point correlation functions of Yang-Mills theory in the Landau gauge by means of a massive extension of the Faddeev-Popov action. This model is based on some phenomenological arguments and constraints on the ultraviolet behavior of the theory. We show that the running coupling constant remains finite at all energy scales (no Landau pole) for $d>2$ and argue that the relevant parameter of perturbation theory is significantly smaller than 1 at all energies. Perturbative results at low orders are therefore expected to be satisfactory and we indeed find a very good agreement between one-loop correlation functions and the lattice simulations, in three and four dimensions. Dimension-2 is shown to play the role of an upper critical dimension, which explains why the lattice predictions are qualitatively different from those in higher dimensions.

We show that the addition of a topological Gauss-Bonnet term to the gravitational action can greatly increase the instability of four-dimensional de Sitter space by favoring the nucleation of black holes. The pair-production rate given by the Euclidean action for the instanton takes the form $\exp (\Delta S)$ where $S$ is the entropy in Einstein-Gauss-Bonnet theory. The coefficient of the Gauss-Bonnet term in the action sets a stability bound on the curvature of empty de Sitter space. For that coefficient in the low-energy effective action of heterotic string theory, the maximal curvature of de Sitter space is, in general, much lower than the Planck scale.

We develop the quantization of unimodular gravity in the Plebanski and Ashtekar formulations and show that the quantum effective action defined by a formal path integral is unimodular. This means that the effective quantum geometry does not couple to terms in the expectation value of energy proportional to the metric tensor. The path integral takes the same form as is used to define spin foam models, with the additional constraint that the determinant of the four-metric is constrained to be a constant by a gauge fixing term. This extends the results of L. Smolin [Phys. Rev. D 80, 084003 (2009)] to the Hilbert space and path integral of loop quantum gravity. We review the proposal of Unruh, Wald, and Sorkin—that the Hamiltonian quantization yields quantum evolution in a physical time variable equal to elapsed four-volume—and discuss how this may be carried out in loop quantum gravity.

The fundamental resonances of near-extremal Kerr black holes due to massive scalar perturbations are derived analytically. We show that there exists a critical mass parameter, ${\mu }_c$, below which increasing the mass $\mu$ of the field increases the oscillation frequency $\Re (\omega )$ of the resonance. On the other hand, above the critical field mass increasing the mass $\mu$ increases the damping rate $\Im (\omega )$ of the mode. We confirm our analytical results by numerical computations.

Recently Kaloper, Kleban, and Martin reexamined the McVittie solution and argued, contrary to a very widely held belief, that the solution contains a black hole in an expanding universe. Here we corroborate their main conclusion but go on to examine, in some detail, a specific solution that asymptotes to the $\Lambda \mathrm{CDM}$ cosmology. We show that part of the boundary of the solution contains the inner bifurcation two-sphere of the Schwarzschild—de Sitter spacetime, and so both the black and white hole horizons together form a partial boundary of this McVittie solution. We go on to show that the null and weak energy conditions are satisfied and that the dominant energy condition is satisfied almost everywhere in the solution. The solution is understood here by way of a systematic construction of a conformal diagram based on detailed numerical integrations of the null geodesic equations. We find that the McVittie solution admits a degenerate limit in which the bifurcation two-sphere disappears. For solutions with a zero cosmological constant, we find no evidence for the development of a weak null singularity. Rather, we find that in this case there is either a black hole to the future of an initial singularity or a white hole to its past.

The Penrose process on rotational energy extraction of the black hole in the original nonprojectable Hořava-Lifshitz gravity is studied. The strong dependence of the extracted energy from the special range of parameters of the Hořava-Lifshitz gravity, such as parameter ${\Lambda }_W$ and specific angular momentum $a$, has been found. Particle acceleration near the rotating black hole in Hořava-Lifshitz gravity has been studied. It is shown that the fundamental parameter of the Hořava-Lifshitz gravity can impose a limitation on the energy of the accelerating particles preventing them from the infinite value.

At a fundamental level the notion of particle (quantum) comes from quantum field theory. From this point of view we estimate corrections to the free particle wave function due to minimum-length deformed quantum mechanics to the first order in the deformation parameter. Namely, in the matrix element $⟨0|\mathit{\Phi }(t,\mathbf{x})|\mathbf{p}⟩$ that in the standard case sets the free particle wave function $\propto \exp (i[\mathbf{p}\mathbf{x}-\epsilon (\mathbf{p})t])$ there appear three kinds of corrections when the field operator is calculated by using the minimum-length deformed quantum mechanics. Starting from the standard (not modified at the classical level) Lagrangian, after the field quantization we get a modified dispersion relation, and besides that we find that the particle’s wave function contains a small fraction of an antiparticle wave function and the backscattered wave. The result leads to interesting implications for black hole physics.

In this work, a minisuperspace model for the projectable Hořava-Lifshitz gravity without the detailed-balance condition is investigated. The Wheeler-DeWitt equation is derived and its solutions are studied and discussed for some particular cases where, due to Hořava-Lifshitz gravity, there is a “potential barrier” nearby $a=0$. For a vanishing cosmological constant, a normalizable wave function of the Universe is found. When the cosmological constant is nonvanishing, the WKB method is used to obtain solutions for the wave function of the Universe. Using the Hamilton-Jacobi equation, one discusses how the transition from quantum to classical regime occurs and, for the case of a positive cosmological constant, the scale factor is shown to grow exponentially, hence recovering the general relativity behavior for the late Universe.

The standard model and its extensions predict multiple phase transitions in the early universe. In addition to the electroweak phase transition, one or several of these could occur at energies close to the weak scale. Such phase transitions can leave their imprint on the relic abundance of TeV-scale dark matter. In this paper, we enumerate several physical features of a generic phase transition and parametrize the effect of each on the relic abundance. In particular, we include among these effects the presence of the scalar field vacuum energy and the cosmological constant, which is sensitive to UV physics. Within the context of the standard model Higgs sector, we find that the relic abundance of generic TeV-scale dark matter is affected by the vacuum energy at the order of a fraction of a percent. For scalar field sectors with strong first-order phase transitions, an order 1% apparent tuning of coupling constants may allow corrections induced by the vacuum energy to be of order unity.

The exact composition of a specific class of compact stars, historically referred to as “neutron stars,” is still quite unknown. Possibilities ranging from hadronic to quark degrees of freedom, including self-bound versions of the latter, have been proposed. We specifically address the suitability of strange star models (including pairing interactions) in this work, in the light of new measurements available for four compact stars. The analysis shows that these data might be explained by such an exotic equation of state, actually selecting a small window in parameter space, but still new precise measurements and also further theoretical developments are needed to settle the subject.

Neutrons cannot possess a quadrupole moment in the vacuum. Nevertheless, we show that, in the presence of an external magnetic field, the neutrons acquire a new type of quadrupole moment $Q^{ij}=\chi {\sigma }^i{B}^j$ involving the components of spin and magnetic field. This “chiral magnetic” quadrupole moment arises from the interplay of the chiral anomaly and the magnetic field; we estimate its value for the neutron in the static limit and find $\chi \simeq 1.35\times {10}^{-2}{\mathrm{fm}}^4$. The detection of the quadrupole moment of the neutron would provide a novel test of the role of the chiral anomaly in low-energy QCD and can be possible in the presence of both magnetic and inhomogeneous electric fields. The quadrupole moment of the neutron may affect, e.g., the properties of neutron stars and magnetars.

Noting the hierarchy between three mixing angles, ${\theta }_{2,3}=\mathcal{O}({\theta }_1^2)$, we present an exact form of the quark mixing matrix, replacing Wolfenstein’s approximate form. In addition, we suggest to rotate the unitarity triangle, using the weak $CP$ phase convention where the phase is located at the (31) element $\sin {\theta }_1\sin {\theta }_2{e}^{i\delta }$ while the (13) element $\sin {\theta }_1\sin {\theta }_3$ is real. For the $(ab)$ unitarity triangle, the base line ($x$-axis) is defined from the product of the first row elements, $V_{1a}{V}_{1b}^{*}$, and the angle between two sides at the origin is defined to be the phase $\delta$. This is a useful definition since every Jarlskog triangle has the angle $\delta$ at the origin, visible directly in the Cabibbo-Kobayashi-Maskawa matrix. It is argued that $\delta$ represents the barometer of the weak $CP$ violation, which can be related to possible Yukawa textures.

We report a new possibility of using the $M_{CT2}$ (Constransverse mass) variable for mass measurement in single step decay chains involving missing particles with moderate transverse momentum. We show that its experimental feasibility is enhanced compared to the corresponding $M_{T2}$-kink method. We apply this method to reconstruct a pair of chargino decay chains.

We investigate the $H$-dibaryon, an $I(J^P)=0(0^{+})$ with $s=-2$, in the chiral and continuum regimes on anisotropic lattices in quenched QCD. Simulations are performed on modest lattices with refined techniques to obtain results with high accuracy over a spatial lattice spacing in the range of $a_s\sim 0.19–0.40\mathrm{fm}$. We present results for the energy difference between the ground state energy of the hexa-quark stranglet and the free two-baryon state from our ensembles. A negative energy shift observed in the chirally extrapolated results leads to the conclusion that the measured hexa-quark state is bound. This is further confirmed by the attractive interaction in the continuum limit with the observed $H$-dibaryon bound by $47\pm 37\mathrm{MeV}$.

We show that the long-range rapidity correlations between the produced charged-hadron pairs from two Balitsky-Fadin-Kuraev-Lipatov parton showers generate considerable azimuthal angle correlations. These correlations have no $1/N_c$ suppression. The effect of gluon saturation on these correlations are discussed and we show that it is important. We show that a pronounced ridgelike structure emerges by going from the Balitsky-Fadin-Kuraev-Lipatov to the saturation region. We show that the ridge structure at high-energy proton-proton and nucleus-nucleus collisions has the same origin and its main feature can be understood due to initial-state effects. Although the effects of final-state interactions in the latter case can be non-negligible.