An interesting approach to the cosmological coincidence problem is to allow dark matter and dark energy to interact with each other also nongravitationally. We consider two general Ansätze for such an interaction and appraise their ability to address the coincidence problem. We determine the average accuracy required on the cosmic expansion rate data to distinguish interacting cosmological models from the conventional $\Lambda \mathrm{CDM}$ scenario. We find that among the planned surveys the Wide Field Infrared Survey Telescope has the best chance to detect an interaction, though at a low significance level. To unambiguously determine the existence of an interaction one must, therefore, combine the said expansion data with other probes.

In this paper we study an SO(10) SUSY GUT with Yukawa unification for the third generation. We perform a global ${\chi }^2$ analysis given to obtain the GUT boundary conditions consistent with 11 low-energy observables, including the top, bottom and tau masses. We assume a universal mass, $m_{16}$, for squarks and sleptons and a universal gaugino mass, $M_{1/2}$. We then analyze the phenomenological consequences for the LHC for 15 benchmark models with fixed $m_{16}=20\mathrm{TeV}$ and with varying values of the gluino mass. The goal of the present work is to (i) evaluate the lower bound on the gluino mass in our model coming from the most recent published data of CMS and (ii) to compare this bound with similar bounds obtained by CMS using simplified models. The bottom line is that the bounds coming from the same-sign dilepton analysis are comparable for our model and the simplified model studied assuming $\mathcal{B}(\tilde{g}\to t\overline{t}{\tilde{\chi }}_1^0)=100\%$. However the bounds coming from the purely hadronic analyses for our model are 10%–20% lower than obtained for the simplified models. This is due to the fact that for our models the branching ratio for the decay $\tilde{g}\to g{\tilde{\chi }}_{1,2}^0$ is significant. Thus there are significantly fewer b-jets. We find a lower bound on the gluino mass in our models with $M_{\tilde{g}}\gtrsim 1000\mathrm{GeV}$. Finally, there is a theoretical upper bound on the gluino mass which increases with the value of $m_{16}$. For $m_{16}\le 30\mathrm{TeV}$, the gluino mass satisfies $M_{\tilde{g}}\le 2.8\mathrm{TeV}$ at 90% C.L. Thus, unless we further increase the amount of fine-tuning, we expect gluinos to be discovered at LHC 14.

In the perturbative QCD (PQCD) approach, we study the direct $CP$ violation in $B^{0,\pm }\to {\rho }^0(\omega ){\pi }^{0,\pm }\to {\pi }^{+}{\pi }^{-}{\pi }^{0,\pm }$ via the $\rho \mathrm{\text{−}}\omega$ mixing mechanism. We find that the $CP$ violation can be enhanced due to a large strong phase difference when the masses of the ${\pi }^{+}{\pi }^{-}$ pairs are in the vicinity of the $\omega$ resonance. Taking into account the $\rho \mathrm{\text{−}}\omega$ mixing, we also compare the $CP$ violation from the naive factorization approach, QCD factorization approach, and PQCD approach. Based on the $B^0{\overline{B}}^0$ mixing, we discuss the effects of ${\overline{B}}^0{B}^0$ mixing for the total $CP$ violation of $B^0\to {\rho }^0(\omega ){\pi }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$, which is time dependent.

We investigate the transverse momentum resummation for top quark pair production at hadron colliders using the soft-collinear effective theory and the heavy-quark effective theory. We derive the factorization formula for $t\overline{t}$ production at the small pair transverse momentum, and show in detail the procedure for calculating the key ingredient of the factorization formula: the next-to-leading order soft functions. We compare our numerical results with experimental data and find that they are consistent within theoretical and experimental uncertainties. To verify the correctness of our resummation formula, we expand it to the next-to-leading order and the next-to-next-to-leading order, and compare those expressions with the exact fixed-order results numerically. Finally, using the results of transverse momentum resummation, we discuss the transverse-momentum-dependent forward-backward asymmetry at the Tevatron.

We perform a Kaluza-Klein inspired rewriting of double field theory by splitting the coordinates into “compact” and “noncompact” directions. There is no truncation of the compact coordinates or their duals, and so this formulation is manifestly $O(d,d)$ invariant, with $d$ the number of compact directions. The action can serve as a starting point for arbitrary Kaluza-Klein ansätze. For a torus background the theory describes the full tower of Kaluza-Klein modes or, in the dual frame, of the winding modes. The Kaluza-Klein vector is a gauge field for the duality-covariantized Courant bracket algebra rather than a Lie algebra. Gauge covariance requires the inclusion of the 2-form gauge potential descending from the Kalb-Ramond field, leading to a structure resembling the tensor hierarchy of gauged supergravity.

We study the stability of Schwarzschild-Tangherlini (ST) black holes in fourth-order gravity which provides a higher dimensional linearized massive equation. The linearized Ricci tensor perturbations are employed to exhibit unstable modes featuring the Gregory-Laflamme (GL) instability of higher dimensional black strings, in comparison to the stable ST black holes in Einstein gravity. It turns out that the GL instability of the ST black holes in fourth-order gravity originates from the massiveness, but not the nature, of fourth-order derivative theories giving ghost states.

We compute the periastron advance using the effective-one-body formalism for binary black holes moving on quasicircular orbits and having spins collinear with the orbital angular momentum. We compare the predictions with the periastron advance recently computed in accurate numerical-relativity simulations and find remarkable agreement for a wide range of spins and mass ratios. These results do not use any numerical-relativity calibration of the effective-one-body model, and stem from two key ingredients in the effective-one-body Hamiltonian: (i) the mapping of the two-body dynamics of spinning particles onto the dynamics of an effective spinning particle in a (deformed) Kerr spacetime, fully symmetrized with respect to the two-body masses and spins, and (ii) the resummation, in the test-particle limit, of all post-Newtonian corrections linear in the spin of the particle. In fact, even when only the leading spin post-Newtonian corrections are included in the effective-one-body spinning Hamiltonian but all the test-particle corrections linear in the spin of the particle are resummed we find very good agreement with the numerical results (within the numerical error for equal-mass binaries and discrepancies of at most 1% for larger mass ratios). Furthermore, we specialize to the extreme mass-ratio limit and derive, using the equations of motion in the gravitational skeleton approach, analytical expressions for the periastron advance, the meridional Lense-Thirring precession and spin precession frequency in the case of a spinning particle on a nearly circular equatorial orbit in Kerr spacetime, including also terms quadratic in the spin.

We investigate the rapid rise of the dressed Polyakov loop in the Nambu–Jona-Lasinio (NJL) model as a function of temperature. In QCD such a behavior is interpreted as a confinement-deconfinement phase transition. However, we demonstrate that in the NJL model this is simply a remnant of the chiral transition.

We study the kinetic theory for a ($2+1$)-dimensional fermionic system with special emphasis on the parity violating properties associated with the fermion mass. The Wigner function approach is used to derive hydrodynamical transport coefficients to the first spatial derivative order. As a first attempt, the collisions between fermions are neglected. The resulting system is dissipationless. The parity violating Hall electric conductivity has the same temperature and chemical potential dependence as the quantum field theory result at one loop. Vorticity dependent transport properties, which were not considered before, also emerge naturally in this approach.

We consider a class of phenomenological modified gravity models where the terms added to the standard Einstein-Hilbert Lagrangian are just a function of the metric only. For linearized perturbations around an isotropic space-time, this class of models is entirely specified by a rank-4 tensor that encodes possibly time-dependent masses for the gravitons. This tensor has the same symmetries as an elasticity tensor, suggesting an interpretation of massive gravity as an effective rigidity of space-time. If we choose a form for this tensor that is compatible with the symmetries of Friedmann-Robertson-Walker and enforce full reparametrization invariance, then the only theory possible is a cosmological constant. However, in the case where the theory is only time translation invariant, the ghost-free massive gravity theory is equivalent to the elastic dark energy scenario with the extra Lorentz violating vector giving rise to 2 transverse and 1 longitudinal degrees of freedom, whereas when one demands spatial translation invariance one is left with a theory where the entropy perturbation is not gauge invariant.

We present a global analysis of the $B\to K^{*}(\to K\pi ){\mu }^{+}{\mu }^{-}$ decay using the recent LHCb measurements of the primary observables $P_{1,2}$ and $P_{4,5,6,8}^{\prime }$. Some of them exhibit large deviations with respect to the Standard Model (SM) predictions. We explain the observed pattern of deviations through a large new physics contribution to the Wilson coefficient of the semileptonic operator ${\mathcal{O}}_9$. This contribution has an opposite sign to the SM one, i.e., reduces the size of this coefficient significantly. A good description of data is achieved by allowing for new physics contributions to the Wilson coefficients ${\mathcal{C}}_7$ and ${\mathcal{C}}_9$ only. We find a $4.5\sigma$ deviation with respect to the SM prediction, combining the large-recoil $B\to K^{*}(\to K\pi ){\mu }^{+}{\mu }^{-}$ observables with other radiative processes. Once low-recoil observables are included the significance gets reduced to $3.9\sigma$. We have tested different sources of systematics, none of them modifying our conclusions significantly. Finally, we propose additional ways of measuring the primary observables through new foldings.

Taking into account the Euler-Heisenberg effective Lagrangian of one-loop nonperturbative quantum electrodynamics (QED) contributions, we formulate the Einstein-Euler-Heisenberg theory and study the solutions of nonrotating black holes with electric and magnetic charges in spherical geometry. In the limit of strong and weak electromagnetic fields of black holes, we calculate the black hole horizon radius, area, and total energy up to the leading order of QED corrections and discuss the black hole irreducible mass, entropy, and maximally extractable energy as well as the Christodoulou-Ruffini mass formula. We find that these black hole quantities receive the QED corrections, in comparison with their counterparts in the Reissner-Nordström solution. The QED corrections show the screening effect on black hole electric charges and the paramagnetic effect on black hole magnetic charges. As a result, the black hole horizon area, irreducible mass, and entropy increase; however, the black hole total energy and maximally extractable energy decrease compared with the Reissner-Nordström solution. In addition, we show that the condition for extremely charged black holes is modified due to the QED correction.

Recently, it has been conjectured that deconfining phase transition in $SU(N_c)$ pure Yang-Mills theories is continuously connected to a quantum phase transition in softly broken $\mathcal{N}=1$ super Yang-Mills on $R^{1,2}\times S^1$. We exploit this conjecture to study the strength of the transition and deconfining temperature as a function of the vacuum angle $\theta$ in pure Yang-Mills. We find that the transition temperature is a decreasing function of $\theta \in [0,\pi )$, in an excellent agreement with recent lattice simulations. We also predict that the transition becomes stronger for the same range of $\theta$, and comment on the $\theta$ dependence in the large $N_c$ limit. More lattice studies are required to test our predictions.

The unique ghost-free mass and nonlinear potential terms for general relativity are presented in a diffeomorphism and local Lorentz invariant vierbein formalism. This construction requires an additional two-index Stückelberg field, beyond the four scalar fields used in the metric formulation, and unveils a new local SL(4) symmetry group of the mass and potential terms, not shared by the Einstein-Hilbert term. The new field is auxiliary but transforms as a vector under two different Lorentz groups, one of them the group of local Lorentz transformations, the other an additional global group. This formulation enables a geometric interpretation of the mass and potential terms for gravity in terms of certain volume forms. Furthermore, we find that the decoupling limit is much simpler to extract in this approach; in particular, we are able to derive expressions for the interactions of the vector modes. We also note that it is possible to extend the theory by promoting the two-index auxiliary field into a Nambu-Goldstone boson nonlinearly realizing a certain spacetime symmetry, and show how it is “eaten up” by the antisymmetric part of the vierbein.

We study static spherically symmetric solutions of massive bigravity theory, free from the Boulware-Deser ghost. We show the recovery of general relativity via the Vainshtein mechanism, in the weak limit of the physical metric. We find a single polynomial equation determining the behavior of the solution for distances smaller than the inverse graviton mass. This equation is generically of the seventh order, while for a specific choice of the parameters of the theory it can be reduced to lower orders. The solution is analytic in different regimes: for distances below the Vainshtein radius (where general relativity is recovered), and in the opposite regime, beyond the Vainshtein radius, where the solution approaches the flat metric.

We study observability of a Kaluza-Klein (KK) excitation of a gluon in a five-dimensional model with a warped geometry at the Large Hadron Collider. In this model, the Standard Model fields reside in the bulk and the third generation quarks couple to the KK gluon strongly. We focus on the processes including three $b$ quarks as a final state where the first KK gluon propagates as an intermediate state. We evaluate a significance of those processes by taking account of kinematical cuts and a detector efficiency at the Large Hadron Collider and find that the significance is lager than $5\sigma$ with the integrated luminosity of $10(100){\mathrm{fb}}^{-1}$ for a certain range of parameters of the model.

Drell-Yan lepton pairs are produced in the process $p\overline{p}\to e^{+}{e}^{-}+X$ through an intermediate ${\gamma }^{*}/Z$ boson. The lepton angular distributions are used to provide information on the electroweak-mixing parameter ${sin}^2{\theta }_W$ via its observable effective-leptonic ${sin}^2{\theta }_W$, or ${sin}^2{\theta }_{\mathrm{eff}}^{\mathrm{lept}}$. A new method to infer ${sin}^2{\theta }_W$ or, equivalently, the $W$-boson mass $M_W$ in the on-shell scheme, is developed and tested using a previous CDF Run II measurement of angular distributions from electron pairs in a sample corresponding to $2.1{\mathrm{fb}}^{-1}$ of integrated luminosity from $p\overline{p}$ collisions at a center-of-momentum energy of 1.96 TeV. The value of ${sin}^2{\theta }_{\mathrm{eff}}^{\mathrm{lept}}$ is found to be $0.2328\pm 0.0011$. Within a specified context of the standard model, this results in ${sin}^2{\theta }_W=0.2246\pm 0.0011$, which corresponds to a $W$-boson mass of $80.297\pm 0.055\mathrm{GeV}/c^2$, in agreement with previous determinations in electron-position collisions and at the Tevatron collider.

Postcollision space-times of the Cartesian product form $M^{\prime }\times M^{\prime \prime }$, where $M^{\prime }$ and $M^{\prime \prime }$ are two-dimensional manifolds, are known with $M^{\prime }$ and $M^{\prime \prime }$ having constant curvatures of equal and opposite sign (for the collision of electromagnetic shock waves) or of the same sign (for the collision of gravitational shock waves). We construct here a new explicit postcollision solution of the Einstein-Maxwell vacuum field equations with a cosmological constant for which $M^{\prime }$ has constant (nonzero) curvature and $M^{\prime \prime }$ has zero curvature.

The properties of charmonium in a strongly coupled QCD-like plasma at finite momentum are studied. This is based upon a “bottom-up” holographic model which has been previously shown to reproduce charmonium phenomenology in vacuum and give a reasonable dissociation temperature at zero momentum. The finite momentum spectral functions are presented and found to be consistent with recent lattice results. The in-medium dispersion relation and momentum dependence of the decay width of $J/\psi$ have also been investigated. We find no signature of a subluminal limiting velocity from the dispersion relation, while we note that the dissociation temperature decreases with momentum faster than previous holographic models. Based upon the dissociation temperature, a maximum momentum for $J/\psi$ in-medium is identified and its phenomenological implications on $J/\psi$ suppression are discussed.

Generalized gauge fields are tensor fields with mixed symmetries. For gravity and higher spins in dimensions greater than four, the fundamental field in the “magnetic representation” is a generalized gauge field. It is shown that the analog of a point source for a generalized gauge field is a special type of brane whose world sheet has another brane interwoven into it: a current within a current. In the case of gravity in higher dimensions, this combined extended object is the generalization of a magnetic pole. The product of the “electric” and “magnetic” strengths is quantized.