A detailed phenomenological analysis of neutral kaon mixing in “little Randall-Sundrum” models is presented. It is shown that the constraints arising from the $CP$-violating quantity ${ϵ}_K$ can, depending on the value of the ultraviolet cutoff, be even stronger than in the original Randall-Sundrum scenario addressing the hierarchy problem up to the Planck scale. The origin of the enhancement is explained, and a bound ${\Lambda }_{\mathrm{UV}}>\mathrm{\text{several}}$ ${10}^3\mathrm{TeV}$ is derived, below which vast corrections to ${ϵ}_K$ are generically unavoidable. Implications for nonstandard $Z^0\to b\overline{b}$ couplings are briefly discussed.

Even in the absence of a sizable tensor contribution, a B-mode polarization can be generated because of the competition between a pseudoscalar background and predecoupling magnetic fields. By investigating the dispersion relations of a magnetoactive plasma supplemented by a pseudoscalar interaction, the total B-mode polarization is shown to depend not only upon the plasma and Larmor frequencies but also on the pseudoscalar rotation rate. If the (angular) frequency channels of a given experiment are larger than the pseudoscalar rotation rate, the only possible source of (frequency-dependent) B-mode autocorrelations must be attributed to Faraday rotation. In the opposite case the pseudoscalar contribution dominates and the total rate becomes, in practice, frequency independent. The B-mode cross correlations can be used, under certain conditions, to break the degeneracy by disentangling the two birefringent contributions.

We examine, in the imaginary-time formalism, the high temperature behavior of $n$-point thermal loops in static Yang-Mills and gravitational fields. We show that in this regime, any hard thermal loop gives the same leading contribution as the one obtained by evaluating the loop integral at zero external energies and momenta.

We study gravitomagnetic effects in the Palatini formalism of $f(R)$ gravity. On using the Kerr-de Sitter metric, which is a solution of $f(R)$ field equations, we calculate the impact of $f(R)$ gravity on the gravitomagnetic precession of an orbiting gyroscope. We show that, even though an $f(R)$ contribution is present in principle, its magnitude is negligibly small and far to be detectable in the present (like GP-B) and foreseeable space missions or observational tests around the Earth.

We have examined in detail the nonrestoration of symmetry at high temperature in a finite-temperature littlest Higgs model, without and with $T$ parity, by evaluating the one-loop-order finite-temperature integrals of the effective potential numerically, without the high-temperature approximation $T\gg m_i$. We observe that in the model without $T$ parity it is not possible to find a transition temperature within the allowed temperature range of the model ($0<T<4f$) if the UV completion factors are those which give the standard model electroweak minimum, as the effective potential always increases with temperature in the positive direction. However, in the case of the model with $T$ parity, it is possible to find a transition temperature with the same set of UV completion factors, as, with the increase of temperature, the effective potential decreases in magnitude in the positive side, becomes negative, and increases in magnitude in the negative side, indicating symmetry breaking at high temperature. This type of symmetry nonrestoration at high temperature has been observed earlier in some models involving pseudo-Nambu-Goldstone bosons. The behavior of the global structure of the effective potential with $T$ parity in the theory indicates a strong first-order electroweak phase transition, conducive to baryogenesis in the early Universe.

We consider the bremsstrahlung energy loss of high-energy partons moving in the quark-gluon plasma, at weak coupling. We show that the rates for these processes receive large $O(g)$ corrections from classical (non-Abelian) plasma physics effects, which are calculated. In the high-energy (deep Landau-Pomeranchuk-Migdal) regime these corrections can be absorbed in a change of the transverse momentum broadening coefficient $\widehat{q}$, which we give to the next-to-leading order. The correction is large even at relatively weak couplings ${\alpha }_s\sim 0.1$, as is typically found for such effects, signaling difficulties with the perturbative expansion. Our approach is based on an effective Euclideanization property of classical physics near the light cone, which allows an effective theory approach in Euclidean space and suggests new possibilities for the nonperturbative lattice study of these effects.

In the Dvali-Gabadadze-Porrati (DGP) model, the “self-accelerating” solution is plagued by a ghost instability, which makes the solution untenable. This fact, as well as all interesting departures from general relativity (GR), are fully captured by a four-dimensional effective Lagrangian, valid at distances smaller than the present Hubble scale. The 4D effective theory involves a relativistic scalar $\pi$, universally coupled to matter and with peculiar derivative self-interactions. In this paper, we study the connection between self-acceleration and the presence of ghosts for a quite generic class of theories that modify gravity in the infrared. These theories are defined as those that at distances shorter than cosmological, reduce to a certain generalization of the DGP 4D effective theory. We argue that for infrared modifications of GR locally due to a universally coupled scalar, our generalization is the only one that allows for a robust implementation of the Vainshtein effect—the decoupling of the scalar from matter in gravitationally bound systems—necessary to recover agreement with solar-system tests. Our generalization involves an internal Galilean invariance, under which $\pi$’s gradient shifts by a constant. This symmetry constrains the structure of the $\pi$ Lagrangian so much so that in 4D there exist only five terms that can yield sizable nonlinearities without introducing ghosts. We show that for such theories in fact there are “self-accelerating” de Sitter solutions with no ghostlike instabilities. In the presence of compact sources, these solutions can support spherically symmetric, Vainshtein-like nonlinear perturbations that are also stable against small fluctuations. We investigate a possible infrared completion of these theories at scales of order of the Hubble horizon, and larger. There are however some features of our theories that may constitute a problem at the theoretical or phenomenological level: the presence of superluminal excitations; the extreme subluminality of other excitations, which makes the quasistatic approximation for certain solar-system observables unreliable due to Cherenkov emission; the very low strong-interaction scale for $\pi \pi$ scatterings.

Via the semiclassical approximation method, we study the $1/2$-spin fermion tunneling from a higher-dimensional black hole. In our work, the Dirac equations are transformed into a simple form, and then we simplify the fermion tunneling research to the study of the Hamilton-Jacobi equation in curved space-time. Finally, we get the fermion tunneling rates and the Hawking temperatures at the event horizon of higher-dimensional black holes. We study fermion tunneling of a higher-dimensional Schwarzschild black hole and a higher-dimensional spherically symmetric quintessence black hole. In fact, this method is also applicable to the study of fermion tunneling from four-dimensional or lower-dimensional black holes, and we will take the rainbow-Finsler black hole as an example in order to make the fact explicit.

We provide the Barrett-Crane spin foam model for quantum gravity with a discrete action principle, consisting in the usual BF term with discretized simplicity constraints which in the continuum turn topological BF theory into gravity. The setting is the same as usually considered in the literature: space-time is cut into 4-simplices, the connection describes how to glue these 4-simplices together and the action is a sum of terms depending on the holonomies around each triangle. We impose the discretized simplicity constraints on disjoint tetrahedra and we show how the Lagrange multipliers distort the parallel transport and the correlations between neighboring simplices. We then construct the discretized BF action using a noncommutative $\star$ product between SU(2) plane waves. We show how this naturally leads to the Barrett-Crane model. This clears up the geometrical meaning of the model. We discuss the natural generalization of this action principle and the spin foam models it leads to. We show how the recently introduced spin foam fusion coefficients emerge with a nontrivial measure. In particular, we recover the Engle-Pereira-Rovelli spin foam model by weakening the discretized simplicity constraints. Finally, we identify the two sectors of Plebanski’s theory and we give the analog of the Barrett-Crane model in the nongeometric sector.

We study the details of preheating in an inflationary scenario in which the standard model Higgs, strongly nonminimally coupled to gravity, plays the role of the inflaton. We find that the Universe does not reheat immediately through perturbative decays, but rather initiates a complex process in which perturbative and nonperturbative effects are mixed. The Higgs condensate starts oscillating around the minimum of its potential, producing $W$ and $Z$ gauge bosons nonperturbatively, due to violation of the so-called adiabaticity condition. However, during each semioscillation, the created gauge bosons partially decay (perturbatively) into fermions. The decay of the gauge bosons prevents the development of parametric resonance, since bosons cannot accumulate significantly at the beginning. However, the energy transferred to the decay products of the bosons is not enough to reheat the Universe, so after about a hundred oscillations, the resonance effects will eventually dominate over the perturbative decays. Around the same time (or slightly earlier), backreaction from the gauge bosons into the Higgs condensate will also start to be significant. Soon afterwards, the Universe is filled with the remnant condensate of the Higgs and a nonthermal distribution of fermions and bosons (those of the standard model), which redshift as radiation and matter, respectively. We compute the distribution of the energy budget among all the species present at the time of backreaction. From there until thermalization, the evolution of the system is highly nonlinear and nonperturbative, and will require a careful study via numerical simulations.

We study modifications to Weinberg-like sum rules in quasiconformal gauge field theories. Beyond the two Weinberg sum rules and the oblique $S$ parameter, we study the pion mass and the $X$ parameter. Especially, we evaluate the pion mass for walking technicolor theories, in particular, minimal walking technicolor, and find contributions of the order of up to several hundred GeV.

We investigate the predictions of a simple extension of the standard model where the Higgs sector is composed of one $\mathrm{SU}(2{)}_L$ doublet and one real triplet. We discuss the general features of the model, including its vacuum structure, theoretical and phenomenological constraints, and expectations for Higgs collider studies. The model predicts the existence of a pair of light charged scalars and, for vanishing triplet vacuum expectation value, contains a cold dark matter candidate. When the latter possibility occurs, the charged scalars are long-lived, leading to a prediction of distinctive single charged track with missing transverse energy or double charged track events at the large hadron collider. The model predicts a significant excess of two-photon events compared to SM expectations due to the presence of a light charged scalar.

We consider quarkonium in a hot quantum chromodynamics (QCD) plasma which, due to expansion and nonzero viscosity, exhibits a local anisotropy in momentum space. At short distances the heavy-quark potential is known at tree level from the hard-thermal loop resummed gluon propagator in anisotropic perturbative QCD. The potential at long distances is modeled as a QCD string which is screened at the same scale as the Coulomb field. At asymptotic separation the potential energy is nonzero and inversely proportional to the temperature. We obtain numerical solutions of the three-dimensional Schrödinger equation for this potential. We find that quarkonium binding is stronger at nonvanishing viscosity and expansion rate, and that the anisotropy leads to polarization of the $P$-wave states.

In the atmospheric neutrino experiments the primary problems are the huge uncertainties of flux, very rapid fall of flux with increase of energy, the energy dependent wide resolutions of energy and zenith angle between true neutrinos and reconstructed neutrinos. These all in together make the choice of binning of the data for chi-square analysis complicated. The large iron calorimeter has the ability to measure the energy and the direction of the muon with high resolution. From the bending of the track in the magnetic field it can also distinguish its charge. We have analyzed the atmospheric neutrino oscillation generating events by Nuance and then considering the muons produced in the charge current interactions as the reconstructed neutrinos. This practically takes into account the major problem of wide resolutions. We have binned the data in three ways: (i) in the grids of $\log E-\log L$ plane, (ii) in the grids of $\log E-\cos {\theta }_{\mathrm{zenith}}$ plane, and (iii) in the bins of $\log (L/E)$. We have performed a marginalized ${\chi }^2$ study over $\Delta m_{32}^2$, ${\theta }_{13}$ and ${\theta }_{23}$ for neutrinos and antineutrinos separately for each method and finally compared the results.

We show that the Euclidean Snyder noncommutative space implies infinitely many different physical predictions. The distinct frameworks are specified by generalized uncertainty relations underlying deformed Heisenberg algebras. Considering the one-dimensional case in the minisuperspace arena, the bouncing Universe dynamics of loop quantum cosmology can be recovered.

We analyze the stability of the Einstein static universe by considering linear homogeneous perturbations in the context of $f(\mathcal{G})$ modified Gauss-Bonnet theories of gravity. By considering a generic form of $f(\mathcal{G})$, the stability region of the Einstein static universe is parametrized by the linear equation of state parameter $w=p/\rho$ and the second derivative $f^{\prime \prime }(\mathcal{G})$ of the Gauss-Bonnet term.

Left-right symmetry including supersymmetry presents an important class of gauge models which may possess natural solutions to many issues of phenomenology. Cosmology of such models indicates a phase transition accompanied by domain walls. Such walls must be unstable in order to not conflict with standard cosmology and can further be shown to assist with open issues of cosmology such as dilution of unwanted relic densities and leptogenesis. In this paper we construct a model of gauge mediated supersymmetry breaking in which parity breaking is also signaled along with supersymmetry breaking and so as to be consistent with cosmological requirements. It is shown that addressing all the stated cosmological issues requires an extent of fine-tuning, while in the absence of fine-tuning, leptogenesis accompanying successful completion of the phase transition is still viable.

Apparently noninvariant terms (ANTs) that appear in loop diagrams for nonlinear sigma models are revisited in lattice perturbation theory. The calculations have been done mostly with dimensional regularization so far. In order to establish that the existence of ANTs is independent of the regularization scheme, and of the potential ambiguities in the definition of the Jacobian of the change of integration variables from group elements to “pion” fields, we employ lattice regularization, in which everything (including the Jacobian) is well defined. We show explicitly that lattice perturbation theory produces ANTs in the four-point functions of the pion fields at one-loop and the Jacobian does not play an important role in generating ANTs.

Non-Abelian vortices of an $SU(2)$ Chern-Simons-Higgs theory in $2+1$ dimensions are constructed numerically. They represent natural counterparts of the $U(1)$ solutions considered by Hong, Kim, and Pac, and by Jackiw and Weinberg. The Abelian embeddings are identified, for all values of the Higgs self-interaction strength $\nu$, resulting in both attractive and repulsive phases. A detailed analysis of the properties of the solutions reveals the existence of a number of unexpected features. For a certain range of the parameter $\nu$, it is shown that the non-Abelian vortices have lower energy than their topologically stable Abelian counterparts The angular momentum of these vortices is analyzed and it is found that unlike the Abelian ones, whose angular momentum and energy are unrelated, there is a nontrivial mass-spin relation of the non-Abelian vortices.

An alternative theory of gravity has recently been proposed by Bekenstein, named tensor-vector-scalar (TeVeS) theory, which can explain many galactic and cosmological observations without the need for dark matter. While this theory passes basic Solar System tests, and has been scrutinized with considerable detail in other weak-field regimes, comparatively little has been done in the strong-field limit of the theory. In this article, with Cowling approximation, we examine the oscillation spectra of neutron stars in TeVeS. As a result, we find that the frequencies of fundamental modes in TeVeS could become lager than those expected in general relativity, while the dependence of frequency of higher overtone on gravitational theory is stronger than that of lower modes. These imprints of TeVeS make it possible to distinguish the gravitational theory in strong-field regime via the observations of gravitational waves, which can provide unique confirmation of the existence of scalar field.