Recently, deeper understanding of QCD emerges from the study of the AdS/CFT correspondence. New results include the properties of quark-gluon plasma and the confinement/deconfinement phase transition, which are both very important for the scenario of the QCD phase transition in the early universe. In this paper, we study some aspects of how the new results may affect the old calculations of the cosmological QCD phase transition, which are mainly based on the studies of perturbative QCD, lattice QCD, and the MIT bag model.

Sneutrino-antisneutrino oscillation can be observed at the CERN LHC by studying a charge asymmetry of the leptons in the final states. We demonstrate this in the context of an anomaly-mediated supersymmetry breaking model which can give rise to a large oscillation probability. The preferred region of the parameter space is characterized by the presence of a sneutrino next-to-lightest supersymmetric particle and a stau lightest supersymmetric particle. We show that the signals studied here have certain correlations with the pattern of the sneutrino oscillation.

We calculate the light hadron spectrum in full QCD using two plus one flavor asqtad sea quarks and domain wall valence quarks. Meson and baryon masses are calculated on a lattice of spatial size $L\approx 2.5\mathrm{fm}$, and a lattice spacing of $a\approx 0.124\mathrm{fm}$, for pion masses as light as $m_{\pi }\approx 300\mathrm{MeV}$, and compared with the results by the MILC Collaboration with asqtad valence quarks at the same lattice spacing. Two- and three-flavor chiral extrapolations of the baryon masses are performed using both continuum and mixed action heavy baryon chiral perturbation theory. Both the three-flavor and two-flavor functional forms describe our lattice results, although the low-energy constants from the next-to-leading order $SU(3)$ fits are inconsistent with their phenomenological values. Next-to-next-to-leading order $SU(2)$ continuum formulae provide a good fit to the data and yield an extrapolated nucleon mass consistent with experiment, but the convergence pattern indicates that even our lightest pion mass may be at the upper end of the chiral regime. Surprisingly, our nucleon masses are essentially linear in $m_{\pi }$ over our full range of pion masses, and we show this feature is common to all recent dynamical calculations of the nucleon mass. The origin of this linearity is not presently understood, and lighter pion masses and increased control of systematic errors will be needed to resolve this puzzling behavior.

The previous proposal (by two of us) of chain inflation with the QCD axion is shown to fail. The proposal involved a series of fast tunneling events, yet here it is shown that tunneling is too slow. We calculate the bubble nucleation rates for phase transitions in the thick wall limit, approximating the barrier by a triangle. A similar problem arises in realization of chain inflation in the string landscape that uses series of minima along the monodromy staircase around the conifold point. The basic problem is that the minima of the potential are too far apart to allow rapid enough tunneling in these two models. We entertain the possibility of overcoming this problem by modifying the gravity sector to a Brans-Dicke theory. However, one would need extremely small values for the Brans-Dicke parameter in the early universe. Many successful alternatives exist, including other axions (with mass scales not set by QCD) or potentials with comparable heights and widths that do not suffer from the problem of slow tunneling and provide successful candidates for chain inflation.

The stochastic vacuum model for QCD, proposed by Dosch and Simonov, is fused with a worldline casting of the underlying theory, i.e. QCD. Important nonperturbative features of the model are studied. In particular, contributions associated with the spin-field interaction are calculated, and the validity of both the loop equations and of the Bianchi identity is explicitly demonstrated. As an application, a simulated meson-meson scattering problem is studied in the Regge kinematical regime. The process is modeled in terms of the helicoidal Wilson contour along the lines introduced by Janik and Peschanski in a related study based on an AdS/CFT-type approach. Working strictly in the framework of the stochastic vacuum model and in a semiclassical approximation scheme, the Regge behavior for the scattering amplitude is demonstrated. Going beyond this approximation, the contribution resulting from boundary fluctuations of the Wilson loop contour is also estimated.

The so-called “quantum inequalities,” and the “quantum interest conjecture,” use quantum field theory to impose significant restrictions on the temporal distribution of the energy density measured by a timelike observer, potentially preventing the existence of exotic phenomena such as “Alcubierre warp drives” or “traversable wormholes.” Both the quantum inequalities and the quantum interest conjecture can be reduced to statements concerning the existence or nonexistence of bound states for a certain one-dimensional quantum mechanical pseudo-Hamiltonian. Using this approach, we shall provide a simple variational proof of one version of the quantum interest conjecture in ($3+1$)-dimensional Minkowski space.

We explore the consequences of the existence of a very large number of light scalar degrees of freedom in the early universe. We distinguish between participator and spectator fields. The former have a small mass, and can contribute to the inflationary dynamics; the latter are either strictly massless or have a negligible VEV. In $N$-flation and generic assisted inflation scenarios, inflation is a cooperative phenomenon driven by $N$ participator fields, none of which could drive inflation on its own. We review upper bounds on $N$, as a function of the inflationary Hubble scale $H$. We then consider stochastic and eternal inflation in models with $N$ participator fields showing that individual fields may evolve stochastically while the whole ensemble behaves deterministically, and that a wide range of eternal inflationary scenarios are possible in this regime. We then compute one-loop quantum corrections to the inflationary power spectrum. These are largest with $N$ spectator fields and a single participator field, and the resulting bound on $N$ is always weaker than those obtained in other ways. We find that loop corrections to the $N$-flation power spectrum do not scale with $N$, and thus place no upper bound on the number of participator fields. This result also implies that, at least to leading order, the theory behaves like a composite single scalar field. In order to perform this calculation, we address a number of issues associated with loop calculations in the Schwinger-Keldysh “in-in” formalism.

In cyclic universe models based on a single scalar field (e.g., the radion determining the distance between branes in M theory), virtually the entire Universe makes it through the ekpyrotic smoothing and flattening phase, bounces, and enters a new epoch of expansion and cooling. This stable evolution cannot occur, however, if scale-invariant curvature perturbations are produced by the entropic mechanism because it requires two scalar fields (e.g., the radion and the Calabi-Yau dilaton) evolving along an unstable classical trajectory. In fact, we show here that an overwhelming fraction of the Universe fails to make it through the ekpyrotic phase; nevertheless, a sufficient volume survives and cycling continues forever provided the dark energy phase of the cycle lasts long enough, of order a trillion years. Two consequences are a new role for dark energy and a global structure of the Universe radically different from that of eternal inflation.

A thermodynamics-based method is presented for differentiating mini black hole creation mechanisms in high energy parton collisions, including scenarios with large compactified extra dimensions and unparticle-enhanced gravity with real scaling dimension $d_{\mathcal{U}}$. Tensor unparticle interactions are shown to mimic the physics of $(2d_{\mathcal{U}}-2)$ noninteger extra spatial dimensions. This yields unique model-dependent production rates, Hawking temperature profiles, and decay multiplicities for black holes of mass $M_{\mathrm{BH}}\sim 1–15\mathrm{TeV}$ that may be created at the LHC and other future colliders.

The strong coupling constants $g_{{\Sigma }_Q{\Lambda }_Q\pi }$ ($Q=b$ and $c$) are studied in the framework of the light cone QCD sum rules using the most general form of the baryonic currents. The predicted coupling constants are used to estimate the decay widths for the ${\Sigma }_Q\to {\Lambda }_Q\pi$ decays which are compared with the predictions of the other approaches and existing experimental data.

Motivated by the possible large direct $CP$ asymmetry of ${\overline{B}}_d^0\to D^{+}{D}^{-}$ decays measured by the Belle Collaboration, we investigate double charm $B_{u,d}$ and $B_s$ decays in the minimal supersymmetric standard model with $R$-parity violation. We derive the bounds on relevant $R$-parity violating couplings from the current experimental data, which show quite consistent measurements among relative collaborations. Using the constrained parameter spaces, we explore $R$-parity violating effects on other observables in these decays, which have not been measured or have not been well measured yet. We find that the $R$-parity violating effects on the mixing-induced $CP$ asymmetries of ${\overline{B}}_d^0\to D^{(*)+}{D}^{(*)-}$ and ${\overline{B}}_s^0\to D_s^{(*)+}{D}_s^{(*)-}$ decays could be very large; nevertheless, the $R$-parity violating effects on the direct $CP$ asymmetries could not be large enough to explain the large direct $CP$ violation of ${\overline{B}}_d^0\to D^{+}{D}^{-}$ from Belle. Our results could be used to probe $R$-parity violating effects and will correlate with searches for direct $R$-parity violating signals in future experiments.

We study charmed baryon resonances that are generated dynamically within a unitary meson-baryon coupled-channel model that treats the heavy pseudoscalar and vector mesons on equal footing as required by heavy-quark symmetry. It is an extension of recent SU(4) models with $t$-channel vector-meson exchanges to an SU(8) spin-flavor scheme, but differs considerably from the SU(4) approach in how the strong breaking of the flavor symmetry is implemented. Some of our dynamically generated states can be readily assigned to recently observed baryon resonances, while others do not have a straightforward identification and require the compilation of more data as well as an extension of the model to $d$-wave meson-baryon interactions and $p$-wave coupling in the neglected $s$- and $u$-channel diagrams. Of several novelties, we find that the ${\Lambda }_c(2595)$, which emerged as a $ND$ quasibound state within the SU(4) approaches, becomes predominantly a $N{D}^{*}$ quasibound state in the present SU(8) scheme.

We search for charmless decays of charged $B$ mesons to the three-body final state $K_S^0{K}_S^0{\pi }^{+}$. Using a data sample of $423.7{\mathrm{fb}}^{-1}$ collected at the ${\rm Y}(4S)$ resonance with the BABAR detector, corresponding to $(465.1\pm 5.1)\times {10}^6$ $B\overline{B}$ pairs, we find no significant signal and determine a 90% confidence level upper limit on the branching fraction of $5.1\times {10}^{-7}$.

For conformal field theories which admit a dual gravitational description in anti–de Sitter space, electrical transport properties, such as conductivity and charge diffusion, are determined by the dynamics of a U(1) gauge field in the bulk and thus obey universality relations at the classical level due to the uniqueness of the Maxwell action. We analyze corrections to these transport parameters due to higher-dimension operators in the bulk action, beyond the leading Maxwell term, of which the most significant involves a coupling to the bulk Weyl tensor. We show that the ensuing corrections to conductivity and the diffusion constant break the universal relation with the U(1) central charge observed at leading order, but are nonetheless subject to interesting bounds associated with causality in the boundary conformal field theory .

We study a holographic model of a relativistic quantum system with a global $U(1)$ symmetry, at nonzero temperature and density. When the temperature falls below a critical value, we find a second-order superfluid phase transition with mean-field critical exponents. In the symmetry-broken phase, we determine the speed of second sound as a function of temperature. As the velocity of the superfluid component relative to the normal component increases, the superfluid transition goes through a tricritical point and becomes first order.

We investigate the large $N$ reduced model of gauge theory on a curved spacetime through the plane wave matrix model. We formally derive the action of the $\mathcal{N}=4$ supersymmetric Yang-Mills theory on $\mathbb{R}\times S^3$ from the plane wave matrix model in the large $N$ limit. Furthermore, we evaluate the effective action of the plane wave matrix model up to the two-loop level at finite temperature. We find that the effective action is consistent with the free energy of the $\mathcal{N}=4$ supersymmetric Yang-Mills theory on $S^3$ at the high temperature limit where the planar contributions dominate. We conclude that the plane wave matrix model can be used as a large $N$ reduced model to investigate nonperturbative aspects of the $\mathcal{N}=4$ supersymmetric Yang-Mills theory on $\mathbb{R}\times S^3$.

The radiation loss of small-amplitude oscillons (very long-living, spatially localized, time-dependent solutions) in one-dimensional scalar field theories is computed in the small-amplitude expansion analytically using matched asymptotic series expansions and Borel summation. The amplitude of the radiation is beyond all orders in perturbation theory and the method used has been developed by Segur and Kruskal in Phys. Rev. Lett. 58, 747 (1987). Our results are in good agreement with those of long-time numerical simulations of oscillons.

We study the gravitational collapse problem of rotating shells in three-dimensional Einstein gravity with and without a cosmological constant. Taking the exterior and interior metrics to be those of stationary metrics with asymptotically constant curvature, we solve the equations of motion for the shells from the Darmois-Israel junction conditions in the corotating frame. We study various collapse scenarios with arbitrary angular momentum for a variety of geometric configurations, including anti-de Sitter, de Sitter, and flat spaces. We find that the collapsing shells can form a BTZ black hole, a three-dimensional Kerr-dS spacetime, and an horizonless geometry of point masses under certain initial conditions. For pressureless dust shells, the curvature singularity is not formed due to the angular momentum barrier near the origin. However when the shell pressure is nonvanishing, we find that for all types of shells with polytropic-type equations of state (including the perfect fluid and the generalized Chaplygin gas), collapse to a naked singularity is possible under generic initial conditions. We conclude that in three dimensions angular momentum does not in general guard against violation of cosmic censorship.

With applications in astroparticle physics in mind, we generalize a method for the solution of the nonlinear, space-homogeneous Boltzmann equation with an isotropic distribution function to arbitrary matrix elements. The method is based on the expansion of the scattering kernel in terms of two cosines of the “scattering angles.” The scattering functions used by previous authors in particle physics for matrix elements in the Fermi approximation are retrieved as lowest order results in this expansion. The method is designed for the unified treatment of reactive mixtures of particles obeying different scattering laws, including the quantum statistical terms for blocking or stimulated emission, in possibly large networks of Boltzmann equations. Although our notation is the relativistic one, as it is used in astroparticle physics, the results can also be applied in the classical case.

We consider the metric perturbations around a stationary rotating Nambu-Goto string in Minkowski spacetime. By solving the linearized Einstein equations, we study the effects of azimuthal frame-dragging around the rotation axis and linear frame-dragging along the rotation axis, the Newtonian logarithmic potential, and the angular deficit around the string as the potential mode. We also investigate gravitational waves propagating off the string and propagating along the string, and show that the stationary rotating string emits gravitational waves toward the directions specified by discrete angles from the rotation axis. Waveforms, polarizations, and amplitudes which depend on the direction are shown explicitly.