We consider an observable very sensitive to the nonzero intrinsic charm (IC) contribution to the proton density. It is the ratio between the differential cross sections of the photon or $Z$-boson and $c$-jet production in the $pp$ collision, $\gamma (Z)+c$, and the $\gamma (Z)$ and the $b$-jet production. It is shown that this ratio can be approximately flat or increasing at large $\gamma (Z)$ transverse momenta $p_T$, and their pseudorapidities $1.5<\eta <2.4$ if the IC contribution is taken into account. On the contrary, in the absence of the IC, this ratio decreases as $p_T$ grows. We also present the ratios of the cross sections integrated over $p_T$ as a function of the IC probability $w$. It is shown that these ratios are mostly independent on the theoretical uncertainties, and such predictions could therefore be much more promising for the search for the intrinsic charm signal at the LHC compared to the predictions for $p_T$ spectra, which significantly depend on these uncertainties.

We present a general framework to study the phase transition of a black hole. Assuming that there is a phase transition, it is shown that without invoking any specific black hole, the critical exponents and the scaling powers can be obtained. We find that the values, which were calculated by taking explicit forms of different black hole spacetimes, are exactly the same. The reason for this universality is also explained. The implication of the analysis is that one does not need to investigate this problem case by case, as researchers are doing right now. We also observe that these values, except for two such quantities, are independent of the details of the spacetime dimensions.

Doubly special relativity (DSR) is an effective model for encoding quantum gravity in flat spacetime. To incorporate DSR into general relativity, one could use “gravity’s rainbow,” where the spacetime background felt by a test particle would depend on its energy. In this scenario, one could rewrite the rainbow metric $g_{\mu \nu }(E)$ in terms of some orthonormal frame fields and use the modified equivalence principle to determine the energy dependence of $g_{\mu \nu }(E)$. Obviously, the form of $g_{\mu \nu }(E)$ depends on the choice of the orthonormal frame. For a static black hole, there are two natural orthonormal frames: the static one hovering above it and the freely falling one along geodesics. The cases with the static orthonormal frame have been extensively studied by many authors. The aim of this paper is to investigate properties of rainbow black holes in the scenario with the free-fall orthonormal frame. We first derive the metric of rainbow black holes and their Hawking temperatures in this free-fall scenario. Then, the thermodynamics of a rainbow Schwarzschild black hole is studied. Finally, we use the brick wall model to compute the thermal entropy of a massless scalar field near the horizon of a Schwarzschild rainbow black hole in this free-fall scenario.

We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti–de Sitter space ${\mathrm{AdS}}_3$) and constant torsion provide exact solutions.

Composite states of electrically charged and QCD-colored hyperquarks (HQs) in a confining $\mathrm{SU}(N_{\mathrm{HC}})$ hypercolor gauge sector are a plausible extension of the standard model at the TeV scale and have been widely considered as an explanation for the tentative LHC diphoton excess. Additional new physics is required to avoid a stable charged hyperbaryon in such theories. We classify renormalizable models allowing the decay of this unwanted relic directly into standard model states, showing that they are significantly restricted if the new scalar states needed for UV completion are at the TeV scale. Alternatively, if hyperbaryon number is conserved, the charged relic can decay into a neutral hyperbaryon. Such theories are strongly constrained by direct detection, if the neutral constituent hyperquark carries color or weak isospin, and by LHC searches for leptoquarks if it is a color singlet. We show that the neutral hyperbaryon can have the observed relic abundance if the confinement scale and the hyperquark mass are above TeV scale, even in the absence of any hyperbaryon asymmetry.

The ${\eta }^{\prime }$ transition form factor is reanalyzed in view of the recent first observation by BESIII of the Dalitz decay ${\eta }^{\prime }\to \gamma e^{+}{e}^{-}$ in both space- and timelike regions at low and intermediate energies using the Padé approximants method. The present analysis provides a suitable parametrization for reproducing the measured form factor in the whole energy region and allows one to extract the corresponding low-energy parameters together with a prediction of their values at the origin, related to ${\mathrm{\Gamma }}_{{\eta }^{\prime }\to \gamma \gamma }$, and the asymptotic limit. The $\eta –{\eta }^{\prime }$ mixing is reassessed within a mixing scheme compatible with the large-$N_c$ chiral perturbation theory at next-to-leading order, with particular attention to the Okubo-Zweig-Iizuka-rule-violating parameters. The $J/\psi$, $Z\to {\eta }^{(\prime )}\gamma$ decays are also considered and predictions are reported.

The four-body contribution of the model-independent radiative corrections to the Dalitz plot of the semileptonic decays of neutral kaons are computed to order $(\alpha /\pi )(q/M_1)$, where $q$ is the momentum transfer and $M_1$ is the kaon mass. The final result is presented in two forms. The first one is given in terms of the triple integration of the bremsstrahlung photon ready to be performed numerically; the second one is a fully analytical expression. This paper is organized to make it accessible and reliable in the analysis of the Dalitz plot of precision experiments involving kaons and is not compromised to fixing the form factors at predetermined values. As a byproduct, gathering together three- and four-body contributions of radiative corrections yields, through a least-squares fit to the measured kaon decay rates, the value $f_{+}^{K^0{\pi }^{-}}|V_{us}|=0.2168(3)$.

The zero to four loop contribution to the cross section $R_{e^{+}{e}^{-}}$ for $e^{+}{e}^{-}\to$ hadrons, when combined with the renormalization group equation, allows for summation of all leading-log, next-to-leading-log, …, next-to-next-to-next-to-leading-log perturbative contributions. It is shown how all logarithmic contributions to $R_{e^{+}{e}^{-}}$ can be summed and that $R_{e^{+}{e}^{-}}$ can be expressed in terms of the log-independent contributions, and once this is done, the running coupling $a$ is evaluated at a point independent of the renormalization scale $\mu$. All explicit dependence of $R_{e^{+}{e}^{-}}$ on $\mu$ cancels against its implicit dependence on $\mu$ through the running coupling $a$ so that the ambiguity associated with the value of $\mu$ is shown to disappear. The renormalization scheme dependency of the “summed” cross section $R_{e^{+}{e}^{-}}$ is examined in three distinct renormalization schemes. In the first two schemes, $R_{e^{+}{e}^{-}}$ is expressible in terms of renormalization scheme-independent parameters ${\tau }_i$ and is explicitly and implicitly independent of the renormalization scale $\mu$. Two of the forms are then compared graphically both with each other and with the purely perturbative results and the renormalization group-summed next-to-next-to-next-to-leading-log results.

Using a data sample of $980{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data taken with the Belle detector operating at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, we report the results of a study of excited ${\mathrm{\Xi }}_c$ states that decay, via the emission of photons and/or charged pions, into ${\mathrm{\Xi }}_c^0$ or ${\mathrm{\Xi }}_c^{+}$ ground state charmed-strange baryons. We present new measurements of the masses of all members of the ${\mathrm{\Xi }}_c^{\prime }$, ${\mathrm{\Xi }}_c(2645)$, ${\mathrm{\Xi }}_c(2790)$, ${\mathrm{\Xi }}_c(2815)$, and ${\mathrm{\Xi }}_c(2980)$ isodoublets, measurements of the intrinsic widths of those that decay strongly, and evidence of previously unknown transitions.

We propose a simple left-right symmetric theory where the neutrino masses are generated at the quantum level. In this context the neutrinos are Majorana fermions and the model has the minimal degrees of freedom in the scalar sector needed for symmetry breaking and mass generation. We discuss the lepton number violating signatures with two charged leptons of different flavor and missing energy at the Large Hadron Collider in order to understand the testability of the theory.

The generation of the circular polarization of gamma ray burst (GRB) photons is discussed in this paper via their interactions with astroparticles in the presence or absence of background fields such as magnetic fields and noncommutative space-time geometry. Solving the quantum Boltzmann equation for GRB photons as a photon ensemble, we discuss the generation of circular polarization (as Faraday conversion phase shift $\mathrm{\Delta }{\varphi }_{\mathrm{FC}}$) of GRBs in the following cases: (i) intermediate interactions, i.e., the Compton scattering of GRBs in the galaxy cluster magnetic field and in the presence of noncommutative space-time geometry, as well as the scattering of GRBs in the cosmic neutrino background (CNB) and cosmic microwave background (CMB); (ii) interactions with particles and fields in shockwaves, i.e., the Compton scattering of GRBs with accelerated charged particles in the presence of magnetic fields. We found that (i) after shockwave crossing, the greatest contribution of $\mathrm{\Delta }{\varphi }_{\mathrm{FC}}$ for energetic GRBs (of the order of GeV and larger) comes from GRB-CMB interactions, but for low-energy GRBs the contributions of the Compton scattering of GRBs in the galaxy cluster magnetic field dominate; (ii) in shockwave crossing, the magnetic field has significant effects on converting a GRB’s linear polarization to a circular one, and this effect can be used to better understand the magnetic profile in shockwaves. The main aim of this work is to study and measure the circular polarization of GRBs for a better understanding of the physics and mechanism of the generation of GRBs and their interactions before reaching us.

QCD with gauge group $SU(N_c)$ flows to an interacting conformal fixed point in three spacetime dimensions when the number of four-component Dirac fermions $N_f\gg N_c$. We study the perturbative stability of this fixed point via the $\epsilon$-expansion about four dimensions. We find that when the number of fermions is lowered to $N_f^{\mathrm{crit}}\approx \frac{11}{2}{N}_c+(6+\frac{4}{N_c})\epsilon$, a certain four-fermion operator becomes relevant and the theory flows to a new infrared fixed point that may be either massless or massive. F-theorem or entanglement monotonicity considerations complement our $\epsilon$-expansion calculation.

The Peccei-Quinn mechanism presents a neat solution to the strong $CP$ problem. As a by-product, it provides an ideal dark matter candidate, “the axion”, albeit with a tiny mass. Axions therefore can act as dark radiation if excited with large momenta after the end of inflation. Nevertheless, the recent measurement of relativistic degrees of freedom from cosmic microwave background radiation strictly constrains the abundance of such extra relativistic species. We show that ultrarelativistic axions can be abundantly produced if the Peccei-Quinn field was initially displaced from the minimum of the potential. This in lieu places an interesting constraint on the axion dark matter window with large decay constant which is expected to be probed by future experiments. Moreover, an upper bound on the reheating temperature can be placed, which further constrains the thermal history of our Universe.

We show that certain three-dimensional Hořava-Lifshitz gravity theories can be written as Chern-Simons gauge theories on various nonrelativistic algebras. The algebras are specific extensions of the Bargmann, Newton-Hooke and Schrödinger algebras each of which has the Galilean algebra as a subalgebra. To show this we employ the fact that Hořava-Lifshitz gravity corresponds to dynamical Newton-Cartan geometry. In particular, the extended Bargmann (Newton-Hooke) Chern-Simons theory corresponds to projectable Hořava-Lifshitz gravity with a local $U(1)$ gauge symmetry without (with) a cosmological constant. Moreover we identify an extended Schrödinger algebra containing three extra generators that are central with respect to the subalgebra of Galilean boosts, momenta and rotations, for which the Chern-Simons theory gives rise to a novel version of nonprojectable conformal Hořava-Lifshitz gravity that we refer to as Chern-Simons Schrödinger gravity. This theory has a $z=2$ Lifshitz geometry as a vacuum solution and thus provides a new framework to study Lifshitz holography.

The precession of a test gyroscope along stable bound equatorial plane orbits around a Kerr black hole is analyzed, and the precession angular velocity of the gyro’s parallel transported spin vector and the increment in the precession angle after one orbital period is evaluated. The parallel transported Marck frame which enters this discussion is shown to have an elegant geometrical explanation in terms of the electric and magnetic parts of the Killing-Yano 2-form and a Wigner rotation effect.

We obtain higher-dimensional solutions for a supercompact star for the Buchdahl-Vaidya-Tikekar metric ansatz. In particular, Vaidya and Tikekar characterized the 3-geometry by a parameter, $K$, which is related to the sign of a density gradient. It turns out that the key pressure isotropy equation continues to have the same Gauss form and, hence, four-dimensional solutions can be taken over to higher dimensions with $K$ satisfying the relation, $K_n=(K_4-n+4)/(n-3)$, where the subscript refers to the dimension of spacetime. Further, $K\ge 0$ is required (otherwise, the density would have the undesirable feature of increasing with radius), and the equality indicates a constant density star described by the Schwarzschild interior solution. This means that, for a given $K_4$, the maximum dimension could only be $n=K_4+4$. Otherwise, $K_n$ will turn negative.

Assuming the validity of the relativity principle, we discuss the implications on relativistic kinematics of a deformation of the Poincaré invariance that preserves the Poincaré algebra, and only modifies its action on spacetime in a Lorentz-invariant way. We show that, in contrast to the case in which the Poincaré algebra is deformed, the action of boosts on two-particle states is not affected, while the addition law of momenta is to a large extent arbitrary. We discuss some nontrivial examples of deformed addition laws related to the Snyder model.

In this paper we explore the validity of the first law of entanglement entropy in the context of topologically massive gravity (TMG). We find that the variation of the holographic entanglement entropy under perturbation from the pure anti–de Sitter background satisfies the first law upon imposing the bulk equations of motion in a given time slice, despite the appearance of instabilities in the bulk for generic gravitational Chern-Simons coupling $\mu$. The Noether-Wald entropy is different from the holographic entanglement entropy in a general boosted frame. However, this discrepancy does not affect the entanglement first law.

The theoretical modeling of gravitational waveforms from binary neutron star mergers requires precise numerical relativity simulations. Assessing convergence of the numerical data and building the error budget is currently challenging due to the low accuracy of general-relativistic hydrodynamics schemes and to the grid resolutions that can be employed in ($3+1$)-dimensional simulations. In this work, we explore the use of high-order weighted-essentially-nonoscillatory (WENO) schemes in neutron star merger simulations and investigate the accuracy of the waveforms obtained with such methods. We find that high-order WENO schemes can be robustly employed for simulating the inspiral-merger phase and they significantly improve the assessment of the waveform’s error budget with respect to finite-volume methods. High-order WENO schemes can be thus efficiently used for high-quality waveform production, and in future large-scale investigations of the binary parameter space.