We explore the possibility of modeling electroweak physics in a warped extra dimension with a soft wall. The infrared boundary is replaced with a smoothly varying dilaton field that provides a dynamical spacetime cutoff. We analyze gravity, gauge fields, and fermions in the soft-wall background and obtain a discrete spectrum of Kaluza-Klein states which can exhibit linear Regge-like behavior. Bulk Yukawa interactions give rise to nonconstant fermion mass terms, leading to fermion localization in the soft-wall background and a possible explanation of the standard model flavor structure. Furthermore we construct electroweak models with custodial symmetry, where the gauge symmetry is broken with a bulk Higgs condensate. The electroweak constraints are not as stringent as in hard-wall models, allowing Kaluza-Klein masses of order the TeV scale.

We introduce an explicit model with technifermion matter transforming according to multiple representations of the underlying technicolor gauge group. The model features simultaneously the smallest possible value of the naive $S$ parameter and the smallest possible number of technifermions. The chiral dynamics is extremely rich. We construct the low-energy effective Lagrangian. We provide both the linearly and nonlinearly realized ones. We then embed, in a natural way, the standard model (SM) interactions within the global symmetries of the underlying gauge theory. Several low-energy composite particles are SM singlets. One of these technicolor interacting massive particles (TIMP)s is a natural cold dark matter (DM) candidate. We estimate the fraction of the mass in the universe constituted by our DM candidate over the baryon one. We show that the new TIMP, differently from earlier models, can be sufficiently light to be directly produced and studied at the Large Hadron Collider (LHC).

In TeV-scale gravity scenarios with large extra dimensions, black holes may be produced at future colliders. Good arguments have been made for why general relativistic black holes may be just out of reach of the Large Hadron Collider (LHC). However, in weakly coupled string theory, highly excited string states—string balls—could be produced at the LHC with high rates and decay thermally, not unlike general relativistic black holes. In this paper, we simulate and study string ball production and decay at the LHC. We specifically emphasize the experimentally detectable similarities and differences between string balls and general relativistic black holes at a TeV scale.

We investigate the Taylor expansion of the baryon number susceptibility, and hence, pressure, in a series in the baryon chemical potential (${\mu }_B$) through a lattice simulation with two flavors of light dynamical staggered quarks at a finer lattice cutoff $a=1/6T$. We determine the QCD cross over coupling at ${\mu }_B=0$. We find the radius of convergence of the series at various temperatures, and bound the location of the QCD critical point to be $T^E/T_c\approx 0.94$ and ${\mu }_B^E/T<1.8$. We also investigate the extrapolation of various susceptibilities and linkages to finite chemical potential.

The spin-dependent interactions in mesons are considered in detail in the framework of the field correlator method. Analytic expressions for the spin-dependent potentials in heavy and light quarkonia are derived with the QCD string moment of inertia taken into account. Recent lattice data are analyzed using these formulae, and the data are shown to be consistent with very small values of the gluonic correlation length $\lesssim 0.1\mathrm{fm}$. The field correlator and the Eichten-Feinberg definitions of the spin-dependent potentials in the lowest, Gaussian approximation for the QCD vacuum are compared with one another, and the two approaches are shown to be equivalent in the limit of a vanishing vacuum correlation length, whereas for finite values of the latter the difference between these two approaches can be explained by the contribution of the higher-order field correlators, starting from the quartic one.

We generate an explicit four-fold infinity of physically acceptable exact perfect fluid solutions of Einstein’s equations by way of conformal transformations of physically unacceptable solutions (one way to view the use of isotropic coordinates). Special cases include the Schwarzschild interior solution and the Einstein static universe. The process we consider involves solving two equations of the Riccati type coupled by a single generating function rather than a specification of one of the two metric functions.

We construct some AdS/QCD models by using the systematic procedure of Gürsoy, Kiritsis, and Nitti. These models cover three different asymptotical ways by which the gauge theory beta functions approach in the infrared region, $\beta \propto -{\lambda }^2$, $-{\lambda }^3$ and $\beta \propto -\lambda$, where $\lambda$ is the ’t Hooft coupling constant. We then calculate the heavy quark potentials in these models by holographic methods and find that they can more consistently fit the lattice data relative to the usual models which do not include the renormalization group improving effects. Since we only use the lattice QCD heavy quark potentials as constraints, we cannot distinguish which kind of infrared asymptotics is better.

We identify a generic new form of collective flavor oscillations in dense neutrino gases that amounts to a self-induced parametric resonance. It occurs in a homogeneous and isotropic ensemble when a range of neutrino modes is prepared in a different flavor than the neighboring modes with lower and higher energies. The flavor content of the intermediate spectral part librates relative to the other parts with a frequency corresponding to a typical $\Delta m^2/2E$. This libration persists in the limit of an arbitrarily large neutrino density where one would have expected synchronized flavor oscillations.

The four-dimensional model with topological mass generation that was found by Dvali, Jackiw, and Pi has recently been generalized to any even number of dimensions ($2n$ dimensions) in a nontrivial manner in which a Stückelberg-type mass term is introduced [S. Deguchi and S. Hayakawa, Phys. Rev. D 77, 045003 (2008)]. The present paper deals with a self-contained model, called here a modified hybrid model, proposed in this $2n$-dimensional generalization and considers the canonical formalism for this model. For the sake of convenience, the canonical formalism itself is studied for a model equivalent to the modified hybrid model by following the recipe for treating constrained Hamiltonian systems. This formalism is applied to the canonical quantization of the equivalent model in order to clarify observable and unobservable particles in the model. The equivalent model (with a gauge-fixing term) is converted to the modified hybrid model (with a corresponding gauge-fixing term) in a Becchi-Rouet-Stora-Tyutin-invariant manner. Thereby it is shown that the Chern-Pontryagin density behaves as an observable massive particle (or field). The topological mass generation is thus verified at the quantum-theoretical level.

We examine what the absorbed spectra of extra-galactic TeV gamma-ray sources, such as blazars, would look like in the presence of Lorentz invariance violation. Pair production with the extra-galactic background light modifies the observed spectra of such sources, and we show that a violation of Lorentz invariance would generically have a dramatic effect on this absorption feature. Inspecting this effect, an experimental task likely practical in the near future, can provide unique insight on the possibility of Lorentz invariance violation.

We reexpress the Kerr metric in standard Bondi-Sachs coordinates near null infinity ${\mathcal{I}}^{+}$. Using the uniqueness result of the characteristic initial value problem, we prove the Kerr metric is the only asymptotically flat, stationary, axially symmetric, type-D solution of the vacuum Einstein equation. The Taylor series of Kerr space-time is expressed in terms of Bondi-Sachs coordinates, and the Newman-Penrose constants have been calculated.

We study the pion in the holographic model of Hirn and Sanz which contains two Yang-Mills fields defined in the background of the sliced AdS space. The infrared boundary conditions imposed on these fields generate the spontaneous breaking of the chiral symmetry down to its vector subgroup. Within the framework of this model, we get an analytic expression for the pion form factor and a compact result for its radius. We also extend the holographic model to include the Chern-Simons term which is required to reproduce the appropriate axial anomaly of QCD. As a result, we calculate the anomalous form factor of the pion and predict its $Q^2$ slope for the kinematics when one of the photons is almost on shell. We also observe that the anomalous form factor with one real and one virtual photon is given by the same analytic expression as the electromagnetic form factor of a charged pion. One of the advantages of the present model is that it does not require an infrared boundary counterterm to correctly reproduce the anomaly of QCD.

In this paper we study the properties of the phase diagram of a simple extra-dimensional model on the lattice at finite temperature. We consider the five-dimensional pure gauge Abelian model with anisotropic couplings which at zero temperature exhibits a new interesting phase, the layer phase. This phase is characterized by a massless photon living on the four-dimensional subspace and confinement along the extra dimension. We show that, as long as the temperature takes a nonzero value, the aforementioned layer phase disappears. It would be equivalent to assume that at finite temperature the higher-dimensional lattice model loses any feature of the layered structure due to the deconfinement which opens up the interactions between the three-dimensional subspaces at finite temperature.

We discuss the chiral phase transition of hot and dense quark matter. We illustrate that the first-order phase transition is generally favored at high baryon density and the repulsive vector-vector interaction weakens the first-order phase transition. We use the Nambu–Jona-Lasinio model with the Polyakov loop coupling for concreteness. We locate the QCD critical surface on the quark mass plane for various values of the vector coupling constant. We find that, with increasing quark chemical potential, the first-order region in the quark mass plane could shrink for sufficiently large vector coupling. This may be a possible explanation for the recent lattice QCD results by de Forcrand and Philipsen.

We study the finite temperature properties of the Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics for a purely spacelike background. Starting from the associated finite temperature partition function, a modified black body spectral distribution is obtained. We thus show that, if the CMB radiation is described by this model, the spectrum presents an anisotropic angular energy density distribution. We show, at leading order, that the Lorentz-breaking contributions for the Plank’s radiation law and for the Stefan-Boltzmann’s law are nonlinear in frequency and quadratic in temperature, respectively. Using our results, we set up bounds for the Lorentz-breaking parameter, and show that Lorentz violation in the context of the MCFJ model is unable to yield the known CMB anisotropy (of 1 part in ${10}^5$).

In previous works, we have constructed a refined version of the Gribov-Zwanziger action in 4 dimensions, by taking into account a novel dynamical effect. In this paper, we explore the 3-dimensional case. Analogously to 4 dimensions, we obtain a ghost propagator behaving like $1/p^2$ in the infrared, while the gluon propagator reaches a finite nonvanishing value at zero momentum. Simultaneously, a clear violation of positivity by the gluon propagator is also found. This behavior of the propagators turns out to be in agreement with the recent numerical simulations.

We employ Coleman-Weinberg and Higgs potentials to implement inflation in nonsupersymmetric grand unified theories (GUTs) such as SU(5) and SO(10). To realize a scalar spectral index close to 0.96, as indicated by the most recent WMAP 5-year analysis, the energy scale of observable inflation turns out to be of order ${10}^{16}\mathrm{GeV}$. This implies a GUT symmetry breaking scale of similar magnitude and proton lifetime of order ${10}^{34}–{10}^{38}\mathrm{years}$. In some SO(10) models with axion dark matter, the scalar leptoquark boson exchange leads to proton decay with a lifetime of order ${10}^{34}–{10}^{35}\mathrm{years}$.

Natural inflation driven by pseudo-Nambu-Goldstone bosons (PNGB) has a problem that the nearly scale invariant spectrum of density perturbations is attained only when the symmetry breaking scale is of the order of Planck scale. We show here that if one couples the PNGB to a thermal bath as in warm inflation models, the amplitude and spectral index which agrees with the Wilkinson Microwave Anisotropy Probe (WMAP) data is obtained with the symmetry breaking in the grand unified theory (GUT) scale. We give a GUT model of PNGB arising out of spontaneously broken lepton number at the GUT scale which gives rise to heavy Majorana masses for the right-handed neutrinos which is needed in seesaw models. This model also generates a lepton asymmetry because of the derivative coupling of the PNGB to the lepton current. A characteristic feature of this model is the prediction of large non-Gaussianity which may be observed in the forthcoming PLANCK experiment.

We present an analytical calculation of the spectra of CMB anisotropies and polarizations generated by relic gravitational waves (RGWs). As a substantial extension to the previous studies, three new ingredients are included in this work. First, the analytic $C_l^{TT}$ and $C_l^{TE}$ are given; especially the latter can be useful to extract signal of RGWs from the observed data in the zero-multipole method. Second, a fitting formula of the decaying factor on small scales is given, coming from the visibility function around the photon decoupling. Third, the impacts by the neutrino free-streaming (NFS) is examined, a process that occurred in the early universe and leaves observable imprints on CMB via RGWs. It is found that the analytic $C_l^{TT}$ and $C_l^{TE}$ have profiles agreeing with the numeric ones, except that $C_l^{TT}$ in a range $l\le 10$ and the first trough of $C_l^{TE}$ around $l\sim 75$ have some deviations. With the new damping factor, the analytic $C_l^{EE}$ and $C_l^{BB}$ match with the numeric ones with the maximum errors only $\sim 3\%$ up to the first three peaks for $l\le 600$, improving the previous studies substantially. The correspondence of the positions of peaks of $C_l^{XX}$ and those of RGWs are also demonstrated explicitly. We also find that NFS reduces the amplitudes of $C_l^{XX}$ by $(20\%\sim 35\%)$ for $l\simeq (100\sim 600)$ and shifts slightly their peaks to smaller angles. Detailed analyses show that the zero multipoles $l_0$, where $C_l^{TE}$ crosses 0, are shifted to larger values by NFS. This shifting effect is as important as those caused by different inflation models and different baryon fractions.

We derive the one loop renormalization group equations for the Cabibbo-Kobayashi-Maskawa (CKM) matrix for the standard model, its two Higgs extension, and the minimal supersymmetric extension in a novel way. The derived equations depend only on a subset of the model parameters of the renormalization group equations for the quark Yukawa couplings so the CKM matrix evolution cannot fully test the renormalization group evolution of the quark Yukawa couplings. From the derived equations we obtain the invariant of the renormalization group evolution for three models which is the angle ${\varphi }_2$ of the unitarity triangle. For the special case of the standard model and its extensions with $v_1\approx v_2$ we demonstrate that also the shape of the unitarity triangle and the Buras-Wolfenstein parameters $\overline{\rho }$ and $\overline{\eta }$ are conserved. The invariance of the angles of the unitarity triangle means that it is not possible to find a model in which the CKM matrix might have a simple, special form at asymptotic energies.