In this paper we analyze the effect of recently proposed classes of sudden future singularities on causal geodesics of FLRW spacetimes. Geodesics are shown to be extendible and just the equations for geodesic deviation are singular, although tidal forces are not strong enough to produce a Big Rip. For the sake of completeness, we compare with the typical sudden future singularities of phantom cosmologies.

We study the matching between the Hawking temperature of a large class of static $D$-dimensional black holes and the Unruh temperature of the corresponding higher dimensional Rindler spacetime. In order to accomplish this task we find the global embedding of the $D$-dimensional black holes into a higher dimensional Minkowskian spacetime, called the global embedding Minkowskian spacetime procedure (GEMS procedure). These global embedding transformations are important on their own, since they provide a powerful tool that simplifies the study of black hole physics by working instead, but equivalently, in an accelerated Rindler frame in a flat background geometry. We discuss neutral and charged Tangherlini black holes with and without cosmological constant, and in the negative cosmological constant case, we consider the three allowed topologies for the horizons (spherical, cylindrical/toroidal, and hyperbolic).

The study of the quasinormal modes (QNMs) of the $2+1$ dimensional rotating draining bathtub acoustic black hole, the closest analogue found so far to the Kerr black hole, is performed. Both the real and imaginary parts of the quasinormal (QN) frequencies as a function of the rotation parameter $B$ are found through a full nonlinear numerical analysis. Since there is no change in sign in the imaginary part of the frequency as $B$ is increased we conclude that the $2+1$ dimensional rotating draining bathtub acoustic black hole is stable against small perturbations.

A spherically symmetric spacetime is presented with an initial data set that is asymptotically flat, satisfies the dominant energy condition, and such that on this initial data $M<\sqrt{A/16\pi }$, where $M$ is the total mass and $A$ is the area of the apparent horizon. This provides a counterexample to a commonly stated version of the Penrose inequality, though it does not contradict the true Penrose inequality.

The propagation and nonlinear interactions of magnetohydrodynamic waves are considered in the force-free limit, where the inertia of the conducting matter which enforces the MHD condition $\mathbf{E}·\mathbf{B}=0$ can be neglected in comparison with the inertia of the electromagnetic field. By extending the analysis beyond the WKB approximation, we are able to study the nonlinearities induced by a gravitational field. We treat the perturbed electromagnetic field as a fluid of infinite conductivity. We calculate the scattering of a torsional (Alfvén) wave by a gravitational potential, and demonstrate a nonlinear coupling with a compressive (fast) wave which is second-order in the amplitude of the Alfvén wave. In a cylindrically symmetric spacetime with slow rotation, the coupling is second-order in $g_{t\varphi }$ and first order in the amplitude of the wave. We also give a fresh analysis of the nonlinear interactions between compressive and torsional waves in Minkowski space, with a focus on the relative strengths of their three- and four-mode interactions. In contrast with nonrelativistic magnetofluids, the effects of compression are always present. In the case of colliding fast waves, a net displacement of the field lines across (at least) one of the colliding wavepackets is shown to have a strong effect on the outgoing waveform, and to have a qualitatively different interpretation than was previously suggested for colliding Alfvén waves. Finally, we show how spacetime curvature modifies the collision between two torsional waves, in both the weak and strong field regimes.

The topcolor-assisted technicolor (TC2) theory predicts tree-level flavor-changing neutral-current (FCNC) top quark Yukawa couplings with top-pions. Such FCNC interactions will induce like-sign top quark pair productions at CERN Large Hadron Collider (LHC). While these rare productions are far below the observable level in the Standard Model and other popular new physics models such as the Minimal Supersymmetric Model, we find that in a sound part of parameter space the TC2 model can enhance the production cross sections to several tens of fb and thus may be observable at the LHC due to rather low backgrounds. Searching for these productions at the LHC will serve as an excellent probe for the TC2 model.

Using 58 million $J/\psi$ events taken with the BES II detector at the Beijing Electron Positron Collider, the decay $J/\psi \to \gamma f_2(1270)f_2(1270)\to \gamma {\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ is observed, and the branching fraction $Br(J/\psi \to \gamma f_2{f}_2)=(9.5\pm 0.7\pm 1.6)\times {10}^{-4}$ is measured for the first time, where the quoted errors are statistical and systematic, respectively. The branching fraction of $J/\psi \to \gamma {\eta }_c$, ${\eta }_c\to f_2{f}_2$ is also measured to be $Br(J/\psi \to \gamma {\eta }_c)·Br({\eta }_c\to f_2{f}_2)=(1.3\pm {0.3}_{-0.4}^{+0.3})\times {10}^{-4}$. The nonresonant branching fraction of $J/\psi \to \gamma f_2{f}_2$ is $Br(J/\psi \to \gamma f_2{f}_2)=(8.2\pm 0.8\pm 1.7)\times {10}^{-4}.$

We provide a mechanism by which, from a background-independent model with no quantum mechanics, quantum theory arises in the same limit in which spatial properties appear. Starting with an arbitrary abstract graph as the microscopic model of spacetime, our ansatz is that the microscopic dynamics can be chosen so that (i) the model has a low-energy limit which reproduces the nonrelativistic classical dynamics of a system of $N$ particles in flat spacetime, (ii) there is a minimum length, and (iii) some of the particles are in a thermal bath or otherwise evolve stochastically. We then construct simple functions of the degrees of freedom of the theory and show that their probability distributions evolve according to the Schrödinger equation. The nonlocal hidden variables required to satisfy the conditions of Bell’s theorem are the links in the fundamental graph that connect nodes adjacent in the graph but distant in the approximate metric of the low-energy limit. In the presence of these links, distant stochastic fluctuations are transferred into universal quantum fluctuations.

We discuss the origin of ultraviolet sensitivity in extra dimensional theories, and compare and contrast the cutoff dependences in universal, nonuniversal, and split five-dimensional models. While the gauge bosons and scalars are in the five-dimensional bulk in all scenarios, the locations of the fermions are different in different cases. In the universal model all fermions can travel in the bulk, in the nonuniversal case they are all confined at the brane, while in the split scenario some are in the bulk and some are in the brane. A possible cure from such divergences is also discussed.

We point out a caveat in the proof for automatic $\mathrm{O}(a)$ improvement in twisted mass lattice QCD at maximal twist angle. With the definition for the twist angle previously given by Frezzotti and Rossi, automatic $\mathrm{O}(a)$ improvement can fail unless the quark mass satisfies $m_q\gg a^2{\Lambda }_{\mathrm{Q}\mathrm{C}\mathrm{D}}^3$. We propose a different definition for the twist angle which does not require a restriction on the quark mass for automatic $\mathrm{O}(a)$ improvement. In order to illustrate explicitly automatic $\mathrm{O}(a)$ improvement we compute the pion mass in the corresponding chiral effective theory. We consider different definitions for maximal twist and show explicitly the absence or presence of the leading $\mathrm{O}(a)$ effect, depending on the size of the quark mass.

In theories with large extra dimensions, we study the top-spin correlations at the Large Hadron Collider. The $s$-channel process mediated by graviton Kaluza-Klein modes contributes to the top-antitop pair production in addition to the standard model processes, and affects the resultant top-spin correlations. We calculated the full density matrix for the top-antitop pair production. With the fundamental scale of the extra dimensional theory below 2 TeV, we find a sizable deviation of the top-spin correlations from the standard model one.

The phase diagram for staggered fermions is discussed in the context of the staggered chiral Lagrangian, extending previous work on the subject. When the discretization errors are significant, there may be an Aoki-like phase for staggered fermions, where the remnant $SO(4)$ taste-symmetry is broken down to $SO(3)$. We solve explicitly for the mass spectrum in the 3-flavor degenerate mass case and discuss qualitatively the $2+1$-flavor case. From numerical results we find that current simulations are outside the staggered-Aoki phase. As for near-future simulations with more-improved versions of the staggered action, it seems unlikely that these will be in the Aoki phase for any realistic value of the quark mass, although the evidence is not conclusive.

A comparative study of commonly used hadronic collision simulation packages is presented. The characteristics of the products of hadron-nucleus collisions are analyzed from a general perspective, but focusing on their correlation with diffractive processes. One of the purposes of our work is to give quantitative estimations of the impact that different characteristics of the hadronic models have on air shower observables. Several sets of shower simulations using different settings for the parameters controlling the diffractive processes are used to analyze the correlations between diffractivity and shower observables. We find that the relative probability of diffractive processes during the shower development have a non-negligible influence over the longitudinal profile as well as the distribution of muons at ground level. The implications on experimental data analysis are discussed.

The ${\eta }_L(1410)$ component of the $\eta (1440)$ pseudoscalar has strong affinity for glue. But its mass is incompatible with lattice simulations that predict a much higher value for the $0^{-+}$ glueball. Consequently it has been suggested that ${\eta }_L(1410)$ signals physics beyond the Standard Model. Here we argue that if glueballs are closed gluonic fluxtubes then ${\eta }_L(1410)$ is a prime candidate for the $0^{-+}$ glueball.

We derive a general effective action for quark matter at nonzero temperature and/or nonzero density. For this purpose, we distinguish irrelevant from relevant quark modes, as well as hard from soft gluon modes by introducing two separate cutoffs in momentum space, one for quarks, ${\Lambda }_q$, and one for gluons, ${\Lambda }_g$. We exactly integrate out irrelevant quark modes and hard gluon modes in the functional integral representation of the QCD partition function. Depending on the specific choice for ${\Lambda }_q$ and ${\Lambda }_g$, the resulting effective action contains well-known effective actions for hot and/or dense quark matter, for instance the “Hard Thermal Loop” or the “Hard Dense Loop” action, as well as the high-density effective theory proposed by Hong and others. We then apply our effective action to review the calculation of the color-superconducting gap parameter to subleading order in weak coupling, where the strong coupling constant $g\ll 1$. In this situation, relevant quark modes are those within a layer of thickness $2{\Lambda }_q$ around the Fermi surface. The nonperturbative nature of the gap equation invalidates naive attempts to estimate the importance of the various contributions via power counting on the level of the effective action. Nevertheless, once the gap equation has been derived within a particular many-body approximation scheme, the cutoffs ${\Lambda }_q,{\Lambda }_g$ provide the means to rigorously power count different contributions to the gap equation. We recover the previous result for the QCD gap parameter for the choice ${\Lambda }_q\lesssim g\mu \ll {\Lambda }_g\lesssim \mu$, where $\mu$ is the quark chemical potential. We also point out how to improve this result beyond subleading order in weak coupling.

We examine the accuracy of ${\theta }_{23}$ determination in future long-baseline (LBL) ${\nu }_{\mu }$ disappearance experiments in the three-flavor mixing scheme of neutrinos. Despite that the error of ${sin}^{2}2{\theta }_{23}$ is indeed a few percent level at around the maximal mixing, we show that the error of physics variable $s_{23}^2$ is large, $\delta (s_{23}^2)/s_{23}^2\simeq 10-20\%$, depending upon regions of ${\theta }_{23}$. The errors are severely affected by the octant degeneracy of ${\theta }_{23}$, and $\delta (s_{23}^2)$ is largely amplified by the Jacobian factor relating these two variables in a region near the maximal mixing. The errors are also affected by the uncertainty due to the unknown value of ${\theta }_{13}$; $\delta (s_{23}^2)$ is doubled at off maximal in the second octant of ${\theta }_{23}$ where the effect is largest. To overcome this problem, we discuss combined analysis with ${\nu }_e$ appearance measurement in LBL experiments, or with reactor measurement of ${\theta }_{13}$. For possible relevance of subleading effects even in the next generation LBL experiments, we give a self-contained derivation of the survival probability to the next to leading order in $s_{13}^2$ and $\Delta m_{21}^2/\Delta m_{31}^2$.

Cross sections and form factors for $e^{+}{e}^{-}\to \omega {\pi }^0$, $\rho \eta$, and $\rho {\eta }^{\prime }$ at center of mass energies of 3.650, 3.686, and 3.773 GeV are measured using data samples collected with the BESII detector at the BEPC. Also, the branching fractions of $\psi (2S)\to \omega {\pi }^0$, $\rho \eta$, and $\rho {\eta }^{\prime }$ are determined to be $({1.87}_{-0.62}^{+0.68}\pm 0.28)\times {10}^{-5}$, $({1.78}_{-0.62}^{+0.67}\pm 0.17)\times {10}^{-5}$, and $({1.87}_{-1.11}^{+1.64}\pm 0.33)\times {10}^{-5}$, respectively.

The generalized second law of gravitational thermodynamics is applied to the present era of accelerated expansion of the Universe. In spite of the fact that the entropy of matter and relic gravitational waves inside the event horizon diminish, the mentioned law is fulfilled provided that the expression for the entropy density of the gravitational waves satisfies a certain condition.

A renormalization group (RG) improvement of the Einstein-Hilbert action is performed which promotes Newton’s constant and the cosmological constant to scalar functions on spacetime. They arise from solutions of an exact RG equation by means of a “cutoff identification” which associates RG scales to the points of spacetime. The resulting modified Einstein equations for spherically symmetric, static spacetimes are derived and analyzed in detail. The modifications of the Newtonian limit due to the RG evolution are obtained for the general case. As an application, the viability of a scenario is investigated where strong quantum effects in the infrared cause Newton’s constant to grow at large (astrophysical) distances. For two specific RG trajectories exact vacuum spacetimes modifying the Schwarzschild metric are obtained by means of a solution-generating Weyl transformation. Their possible relevance to the problem of the observed approximately flat galaxy rotation curves is discussed. It is found that a power law running of Newton’s constant with a small exponent of the order ${10}^{-6}$ would account for their non-Keplerian behavior without having to postulate the presence of any dark matter in the galactic halo.