Einstein’s theory of general relativity was formulated as a gauge theory of Lorentz symmetry by Utiyama in 1956, while the Einstein-Cartan gravitational theory was formulated by Kibble in 1961 as the gauge theory of Poincaré transformations. In this framework, we propose a formulation of the gravitational theory on canonical noncommutative space-time by covariantly gauging the twisted Poincaré symmetry, in order to fulfil the requirement of covariance under the general coordinate transformations, an essential ingredient of the theory of general relativity. It appears that the twisted Poincaré symmetry cannot be gauged by generalizing the Abelian twist to a covariant non-Abelian twist, nor by introducing a more general covariant twist element. The advantages of such a formulation as well as the related problems are discussed and possible ways out are outlined.

The discrepancy on ${}^7\mathrm{Li}$ and ${}^6\mathrm{Li}$ abundances between the observational data and the standard big-bang nucleosynthesis theory prediction has been a nagging problem in astrophysics and cosmology, given the highly attractive and successful big-bang paradigm. One possible solution of this lithium problem is through hadronic decays of a massive metastable particle which alter the primordial element abundances. We explore this possibility using a gravitino dark matter framework in which the next lightest supersymmetric particle is typically long-lived. We found that the stop as the next lightest supersymmetric particle may provide an attractive solution to the lithium problem.

We establish the fundamental properties of two classes of interferometers: those forming a pattern in momentum space, based on the superposition of two different momentum states and described by their relative propagation, and those forming a pattern in real space, based on two or more interferometer arms and described by the propagation between their local ends. These two classes are characterized by different sensitivity functions and different noise sources; we will compare the sensitivity functions of two possible configurations of atom interferometer and identify the most promising realization, with a view to applications to tests of general relativity and investigations of alterations of the spacetime curvature.

We combine the “evolving constants” approach to the construction of observables in canonical quantum gravity with the Page-Wootters formulation of quantum mechanics with a relational time for generally covariant systems. This overcomes the objections levied by Kuchař against the latter formalism. The construction is formulated entirely in terms of Dirac observables, avoiding in all cases the physical observation of quantities that do not belong in the physical Hilbert space. We work out explicitly the example of the parametrized particle, including the calculation of the propagator. The resulting theory also predicts a fundamental mechanism of decoherence.

We study the potential of the CERN large hadron collider to probe the spin of new massive vector boson resonances predicted by Higgsless models. We consider its production via weak boson fusion which relies only on the coupling between the new resonances and the weak gauge bosons. We show that the large hadron collider will be able to unravel the spin of the particles associated with the partial restoration of unitarity in vector boson scattering for integrated luminosities of $150–560{\mathrm{fb}}^{-1}$, depending on the new state mass and on the method used in the analyses.

In a class of anomaly mediated supersymmetry breaking (AMSB) models, the splitting in the $W$-ino multiplet turns out to be very small, such as the often-quoted 170 MeV in minimal AMSB, which originates from minimal supersymmetric standard model loops. Such a small mass gap is potentially a window into higher scale physics, as it may be sensitive to higher-dimensional operators. We show that still within AMSB one can get a much larger splitting in the $W$-ino multiplet—a few GeV—if the scale of the new physics is comparable to the gravitino mass (which is indeed often the scale of new physics in anomaly mediation).

Baryon distribution amplitudes (DAs) are crucial for the theory of hard exclusive reactions. We present a calculation of the first few moments of the leading-twist nucleon DA within lattice QCD. In addition we deal with the normalization of the next-to-leading (twist-four) DAs. The matrix elements determining the latter quantities are also responsible for proton decay in grand unified theories. Our lattice evaluation makes use of gauge field configurations generated with two flavors of clover fermions. The relevant operators are renormalized nonperturbatively with the final results given in the $\overline{\mathrm{MS}}$ scheme. We find that the deviation of the leading-twist nucleon DA from its asymptotic form is less pronounced than sometimes claimed in the literature.

The $B_{u,d,s}\to V$, $A$ form factors are studied in the perturbative QCD approach ($V$, $A$ denote a vector meson and two kinds of $p$-wave axial-vector mesons: ${}^{3}P_1$ and ${}^{1}P_1$ states, respectively). The form factors are directly studied in the large recoiling region and extrapolated to the whole kinematic region within the dipole parametrization. Adopting decay constants with different signs for the two kinds of axial vectors, we find that the two kinds of $B\to A$ form factors have the same sign. The two strange mesons $K_{1A}$ and $K_{1B}$ mix with each other via the SU(3) symmetry breaking effect. In order to reduce the ambiguities in the mixing angle between $K_{1A}$ and $K_{1B}$, we propose a model-independent way that utilizes the $B$ decay data. Most of the branching fractions of the semilteptonic $B\to Al{\overline{\nu }}_l$ decays are of the order ${10}^{-4}$, which still need experimental tests in the ongoing and forthcoming experiments.

We consider theories with an arbitrary coupling between matter and gravity and obtain the perturbation equation of matter on subhorizon scales. Also, we derive the effective gravitational constant $G_{\mathrm{eff}}$ and two parameters $\Sigma$ and $\eta$, which along with the perturbation equation of the matter density are useful to constrain the theory from growth factor and weak lensing observations. Finally, we use a completely solvable toy model which exhibits nontrivial phenomenology to investigate specific features of the theory. We obtain the analytic solution of the modified Friedmann equation for the scale factor $a$ in terms of time $t$ and use the age of the oldest star clusters and the primordial nucleosynthesis bounds in order to constrain the parameters of our toy model.

Inelastic dark matter, in which weakly interacting massive particle (WIMP)-nucleus scatterings occur through a transition to an excited WIMP state $\sim 100\mathrm{keV}$ above the ground state, provides a compelling explanation of the DAMA annual modulation signal. We demonstrate that the relative sensitivities of various dark matter direct detection experiments are modified such that the DAMA annual modulation signal can be reconciled with the absence of a reported signal at CDMS-Soudan, XENON10, ZEPLIN, CRESST, and KIMS for inelastic WIMPs with masses $O(100\mathrm{GeV})$. We review the status of these experiments, and make predictions for upcoming ones. In particular, we note that inelastic dark matter leads to highly suppressed signals at low energy, with most events typically occurring between 20 and 45 keV (unquenched) at xenon and iodine experiments, and generally no events at low ($\sim 10\mathrm{keV}$) energies. Suppressing the background in this high-energy region is essential to testing this scenario. The recent CRESST data suggest seven observed tungsten events, which is consistent with expectations from this model. If the tungsten signal persists at future CRESST runs, it would provide compelling evidence for inelastic dark matter, while its absence should exclude it.

Precision data from cosmology suggest neutrinos stream freely and hence interact very weakly around the epoch of recombination. We study this issue in a simple framework where neutrinos recouple instantaneously and stop streaming freely at a redshift $z_i$. The latest cosmological data imply $z_i\lesssim 1500$, the exact constraint depending somewhat on the assumed prior on $z_i$. This bound can be translated into a bound on the coupling strength between neutrinos and majoronlike particles.

Motivated by the holographic principle, it has been suggested that the dark energy density may be inversely proportional to the area of the event horizon of the Universe. However, such a model would have a causality problem. In this paper, we propose to replace the future event horizon area with the inverse of the Ricci scalar curvature. We show that this model does not only avoid the causality problem and is phenomenologically viable, but also naturally solves the coincidence problem of dark energy. Our analysis of the evolution of density perturbations show that the matter power spectra and cosmic microwave background temperature anisotropy is only slightly affected by such modification.

Based on the approach of the vector form factor $F_{B\to \pi ,K}^{+}(q^2)$ in our previous papers, we extend the calculation of the radiative corrections to the $B\to P$ ($P$ stands $\pi$, $K$, and all light pseudoscalar mesons) scalar and tensor form factors $F_{B\to P}^{0,T}(q^2)$ with chiral current in the light-cone sum rules (LCSRs). The most uncertain twist-3 contributions to the $B\to P$ form factors can be naturally eliminated through a properly designed correlator. We present the next-leading-order formulas of $F_{B\to P}^{+,0,T}(q^2)$ with the $b$-quark pole mass that is universal. It has been shown that our results are simpler and less uncertain under the same parameter regions since we only need to calculate the next-leading order on the twist-2 part from the obtained LCSR. Second, we obtain $f_{B\to \pi }^{+,0}(0)={0.260}_{-0.040}^{+0.059}$, $f_{B\to \pi }^T(0)={0.276}_{-0.039}^{+0.052}$, $f_{B\to K}^{+,0}(0)={0.334}_{-0.069}^{+0.094}$, and $f_{B\to K}^T(0)={0.379}_{-0.077}^{+0.092}$ at $q^2=0$ and the $S{U}_f(3)$-breaking effects are discussed too.

We investigate the process of phase conversion in a thermally driven weakly first-order quark-hadron transition. This scenario is physically appealing even if the nature of this transition in equilibrium proves to be a smooth crossover for vanishing baryonic chemical potential. We construct an effective potential by combining the equation of state obtained within lattice QCD for the partonic sector with that of a gas of resonances in the hadronic phase, and present numerical results on bubble profiles, nucleation rates, and time evolution, including the effects from reheating on the dynamics for different expansion scenarios. Our findings confirm the standard picture of a cosmological first-order transition, in which the process of phase conversion is entirely dominated by nucleation, also in the case of a weakly first-order transition. On the other hand, we show that, even for expansion rates much lower than those expected in high-energy heavy-ion collisions, nucleation is very unlikely, indicating that the main mechanism of phase conversion is spinodal decomposition. Our results are compared to those obtained for a strongly first-order transition, as the one provided by the MIT bag model.

We propose a scheme to assign a 4-momentum to each WIMP in new physics event producing a pair of mother particles each of which decays to an invisible weakly interacting massive particle (WIMP) plus some visible particle(s). The transverse components are given by the value that determines the event variable $M_{T2}$, while the longitudinal component is determined by the on-shell condition on the mother particle. Although it does not give the true WIMP momentum in general, this $M_{T2}$-assisted on-shell reconstruction of missing momenta provides kinematic variables well correlated to the true WIMP momentum and thus can be useful for an experimental determination of new particle properties. We apply this scheme to some processes to measure the mother particle spin and find that spin determination is possible even without good knowledge of the new particle masses.

We calculate leading long-distance noncommutative corrections to the classical Schwarzschild black hole sourced by a massive noncommutative scalar field. The energy-momentum tensor is taken $\mathcal{O}({\ell }^4)$ in the noncommutative parameter $\ell$ and is treated in the semiclassical (tree-level) approximation. These noncommutative corrections dominate classical post-post-Newtonian corrections if $\ell >1/M_P$. However, they are still very small to be observable in present-day experiments.

A gravity theory called scalar-tensor-vector gravity (STVG) has been recently developed and succeeded in solar system, astrophysical, and cosmological scales without dark matter [1]. However, two assumptions have been used: (i) $B(r)=A^{-1}(r)$, where $B(r)$ and $A(r)$ are $g_{00}$ and $g_{rr}$ in the Schwarzschild coordinates (static and spherically symmetric); (ii) scalar field $G=\mathrm{Const}.$ in the solar system. These two assumptions actually imply that the standard parametrized post-Newtonian parameter $\gamma =1$. In this paper, we relax these two assumptions and study STVG further by using the post-Newtonian approximation approach. With abandoning the assumptions, we find $\gamma \ne 1$ in general cases of STVG. Then, a version of modified STVG is proposed through introducing a coupling function of scalar field $G$: $\theta (G)$. We have derived the metric and equations of motion in 1PN for general matter without specific equation of state and $N$ point masses firstly. Subsequently, the secular periastron precession $\dot{\omega }$ of binary pulsars in harmonic coordinates is given. After discussing two parametrized post-Newtonian parameters ($\gamma$ and $\beta$) and two Yukawa parameters ($\alpha$ and $\lambda$), we use $\dot{\omega }$ of four binary pulsars data (PSR $\mathrm{B}1913+16$, PSR $\mathrm{B}1534+12$, PSR $\mathrm{J}0737-3039$, and PSR $\mathrm{B}2127+11\mathrm{C}$) to constrain the Yukawa parameters for modified STVG: $\lambda =(3.97\pm 0.01)\times {10}^8\mathrm{m}$ and $\alpha =(2.40\pm 0.02)\times {10}^{-8}$ if we fix $|2\gamma -\beta -1|=0$.

The Hamiltonian thermodynamics formalism is applied to the general $d$-dimensional Reissner-Nordström-anti-de Sitter black hole with spherical, planar, and hyperbolic horizon topology. After writing its action and performing a Legendre transformation, surface terms are added in order to guarantee a well-defined variational principle with which to obtain sensible equations of motion, and also to allow later on the thermodynamical analysis. Then a Kuchař canonical transformation is done, which changes from the metric canonical coordinates to the physical parameters coordinates. Again, a well-defined variational principle is guaranteed through boundary terms. These terms influence the falloff conditions of the variables and at the same time the form of the new Lagrange multipliers. Reduction to the true degrees of freedom is performed, which are the conserved mass and charge of the black hole. Upon quantization a Lorentzian partition function $Z$ is written for the grand canonical ensemble, where the temperature $\mathbf{T}$ and the electric potential $\varphi$ are fixed at infinity. After imposing Euclidean boundary conditions on the partition function, the respective effective action $I_{*}$, and thus the thermodynamical partition function, is determined for any dimension $d$ and topology $k$. This is a quite general action. Several previous results can be then condensed in our single general formula for the effective action $I_{*}$. Phase transitions are studied for the spherical case, and it is shown that all the other topologies have no phase transitions. A parallel with the Bose-Einstein condensation can be established. Finally, the expected values of energy, charge, and entropy are determined for the black hole solution.

Dark stars powered by dark matter annihilation have been proposed as the first luminous sources in the Universe. These stars are believed to form in the central dark matter cusp of low-mass minihalos. Recent calculations indicate stellar masses up to $\sim 1000M_{\odot }$ and/or have very long lifetimes. The UV photons from these objects could therefore contribute significantly to cosmic reionization. Here we show that such dark star models would require a somewhat artificial reionization history, based on a double-reionization phase and a late star burst near redshift $z\sim 6$, in order to fulfill the WMAP (Wilkinson Microwave Anisotropy Probe) constraint on the optical depth as well as the Gunn-Peterson constraint at $z\sim 6$. This suggests that, if dark stars were common in the early universe, then models are preferred which predict a number of UV photons similar to conventional Pop. III stars. This excludes $800M_{\odot }$ dark stars that enter a main-sequence phase and other models that lead to a strong increase in the number of UV photons. We also derive constraints for massive as well as light dark matter candidates from the observed x-ray, gamma-ray, and neutrino background, considering dark matter profiles which have been steepened during the formation of dark stars. This increases the clumping factor at high redshift and gives rise to a higher dark matter annihilation rate in the early universe. We furthermore estimate the potential contribution from the annihilation products in the remnants of dark stars, which may provide a promising path to constrain such models further, but which is currently still uncertain.