We consider the two-dimensional $\mathcal{N}=(2,2)$ Wess-Zumino model with a cubic superpotential at weak and intermediate couplings. Refined algorithms allow for the extraction of reliable masses in a region where perturbation theory no longer applies. We scrutinize the Nicolai improvement program, which guarantees lattice supersymmetry, and compare the results for ordinary and nonstandard Wilson fermions with those for SLAC derivatives. It turns out that this improvement leads to better results for SLAC fermions but not for Wilson fermions. Furthermore, even without improvement terms the models with all three fermion species reproduce the correct values for the fermion masses in the continuum limit.

The pion-baryon sigma terms and the strange-quark condensates of the octet and the decuplet baryons are calculated by employing the method of QCD sum rules. We evaluate the vacuum-to-vacuum transition matrix elements of two baryon interpolating fields in an external isoscalar-scalar field and use a Monte Carlo-based approach to systematically analyze the sum rules and the uncertainties in the results. We extract the ratios of the sigma terms, which have rather high accuracy and minimal dependence on QCD parameters. We discuss the sources of uncertainties and comment on possible strangeness content of the nucleon and the Delta.

In this paper, we develop approximative two-flavor neutrino oscillation formulas including subleading nonstandard interaction effects. Especially, the limit when the small mass-squared difference approaches zero is investigated. The approximate formulas are also tested against numerical simulations in order to determine their accuracy and they will probably be most useful in the GeV energy region, which is the energy region where most upcoming neutrino oscillation experiments will be operating. Naturally, it is important to have analytical formulas in order to interpret the physics behind the degeneracies between standard and nonstandard parameters.

The five-dimensional stable de Sitter ground states in $\mathcal{N}=2$ supergravity obtained by gauging $SO(1,1)$ symmetry of the real symmetric scalar manifold (in particular, a generic Jordan family manifold of the vector multiplets) simultaneously with a subgroup $R_s$ of the $R$-symmetry group descend to four-dimensional de Sitter ground states under certain conditions. First, the holomorphic section in four dimensions has to be chosen carefully by using the symplectic freedom in four dimensions; second, a group contraction is necessary to bring the potential into a desired form. Under these conditions, stable de Sitter vacua can be obtained in dimensionally reduced theories (from 5D to 4D) if the semidirect product of $SO(1,1)$ with ${\mathbb{R}}^{(1,1)}$ together with a simultaneous $R_s$ is gauged. We review the stable de Sitter vacua in four dimensions found in earlier literature for $\mathcal{N}=2$ Yang-Mills Einstein supergravity with the $SO(2,1)\times R_s$ gauge group in a symplectic basis that comes naturally after dimensional reduction. Although this particular gauge group does not descend directly from five dimensions, we show that its contraction does. Hence, two different theories overlap in certain limits. Examples of stable de Sitter vacua are given for the cases: (i) $R_s=U(1{)}_R$, (ii) $R_s=SU(2{)}_R$, and (iii) $\mathcal{N}=2$ Yang-Mills/Einstein supergravity theory coupled to a universal hypermultiplet. We conclude with a discussion regarding the extension of our results to supergravity theories with more general homogeneous scalar manifolds.

We solve one of the open problems in Einstein-Cartan theory, namely, we find a natural matter source whose spin angular momentum tensor is compatible with the cosmological principle. We analyze the resulting evolution equations and find that an epoch of accelerated expansion is an attractor. The torsion field quickly decays in that period. Our results are interpreted in the context of the standard model of cosmology.

We reexamine the two-point correlation of density maxima in Gaussian initial conditions. Spatial derivatives of the linear density correlation, which were ignored in the calculation of Bardeen et al. [Astrophys. J. 304, 15 (1986)], are included in our analysis. These functions exhibit large oscillations around the sound horizon scale for generic cold dark matter (CDM) power spectra. We derive the exact leading-order expression for the correlation of density peaks and demonstrate the contribution of those spatial derivatives. In particular, we show that these functions can modify significantly the baryon acoustic signature of density maxima relative to that of the linear density field. The effect depends upon the exact value of the peak height, the filter shape and size, and the small-scale behavior of the transfer function. In the $\Lambda \mathrm{CDM}$ cosmology, for maxima identified in the density field smoothed at mass scale $M\approx {10}^{12}–{10}^{14}{\mathrm{M}}_{\odot }/h$ and with linear threshold height $\nu =1.673/\sigma (M)$, the contrast of the baryon acoustic oscillations (BAO) can be a few tens of percent larger than in the linear matter correlation. Overall, the BAO is amplified for $\nu \gtrsim 1$ and damped for $\nu \lesssim 1$. Density maxima thus behave quite differently than linearly biased tracers of the density field, whose acoustic signature is a simple scaled version of the linear baryon acoustic oscillation. We also calculate the mean streaming of peak pairs in the quasilinear regime. We show that the leading-order 2-point correlation and pairwise velocity of density peaks are consistent with a nonlinear, local biasing relation involving gradients of the density field. Biasing will be an important issue in ascertaining how much of the enhancement of the BAO in the primeval correlation of density maxima propagates into the late-time clustering of galaxies.

It has been argued that the spacetime of our universe can be accurately described by a perturbed conformal Newtonian metric, and hence even large density inhomogeneities in a dust universe cannot change the observables predicted by the homogeneous dust model. In this paper we study a spherically symmetric dust model and illustrate conditions under which large spatial variations in the expansion rate can invalidate the argument.

One of the goals of NASA’s Fermi Gamma-ray Space Telescope (formerly GLAST) will be the detection of gamma rays from dark-matter annihilation in the Galactic halo. Theoretical arguments suggest that dark matter may be bound into subhalos with masses as small as ${10}^{-4}–{10}^2{M}_{\oplus }$. If so, it may be possible to detect individual subhalos as point sources in the Fermi Telescope. It has further been argued that some of these point sources may exhibit proper motions. Here we show that upper limits to the diffuse gamma-ray background constrain the number of subhalos close enough to exhibit proper motions to be less than one.

In the dense supernova core, self-interactions may align the flavor polarization vectors of $\nu$ and $\overline{\nu }$ and induce collective flavor transformations. Different alignment Ansätze are known to describe approximately the phenomena of synchronized or bipolar oscillations and the split of $\nu$ energy spectra. We discuss another phenomenon observed in some numerical experiments in inverted hierarchy, showing features akin to a low-energy split of $\overline{\nu }$ spectra. The phenomenon appears to be approximately described by another alignment Ansatz which, in the considered scenario, reduces the (nonadiabatic) dynamics of all energy modes to only two $\nu$ plus two $\overline{\nu }$ modes. The associated spectral features, however, appear to be fragile when passing from single to multiangle simulations.

We study quark mass matrices in the Randall-Sundrum (RS) model with bulk symmetry $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$. The Yukawa couplings are assumed to be within an order of magnitude of each other, and perturbative. We find that quark mass matrices of the symmetrical form proposed by Koide et al. [Y. Koide, H. Nishiura, K. Matsuda, T. Kikuchi, and T. Fukuyama, Phys. Rev. D 66, 093006 (2002)] can be accommodated in the RS framework with the assumption of hierarchyless Yukawa couplings, but not the Hermitian Fritzsch-type mass matrices. General asymmetrical mass matrices are also found which fit well simultaneously with the quark masses and the Cabibbo-Kobayashi-Maskawa matrix. Both left-handed (LH) and right-handed (RH) quark rotation matrices are obtained that allow analysis of flavor changing decay of both LH and RH top quarks. At a warped down scale of 1.65 TeV, the total branching ratio of $t\to Z+\mathrm{\text{jets}}$ can be as high as $\sim 5\times {10}^{-6}$ for symmetrical mass matrices and $\sim 2\times {10}^{-5}$ for asymmetrical ones. This level of signal is within reach of the LHC.

Electroweak precision data has been extensively used to constrain models containing physics beyond that of the standard model. When the model contains Higgs scalars in representations other than $SU(2)$ singlets or doublets, and hence $\rho \ne 1$ at tree level, a correct renormalization scheme requires more inputs than the three needed for the standard model. We discuss the connection between the renormalization of models with Higgs triplets and the decoupling properties of the models as the mass scale for the scalar triplet field becomes much larger than the electroweak scale. The requirements of perturbativity of the couplings and agreement with electroweak data place strong restrictions on models with Higgs triplets. Our results have important implications for Little Higgs type models and other models with $\rho \ne 1$ at tree level.

We propose a nonperturbative definition of $\mathcal{N}=4$ super Yang-Mills (SYM). We realize $\mathcal{N}=4$ SYM on $R\times S^3$ as the theory around a vacuum of the plane wave matrix model. Our regularization preserves 16 supersymmetries and the gauge symmetry. We perform the 1-loop calculation to give evidences that the superconformal symmetry is restored in the continuum limit.

We introduce two new diagnostics of dark energy (DE). The first, $Om$, is a combination of the Hubble parameter and the cosmological redshift and provides a null test of dark energy being a cosmological constant $\Lambda$. Namely, if the value of $Om(z)$ is the same at different redshifts, then $\mathrm{DE}\equiv \Lambda$, exactly. The slope of $Om(z)$ can differentiate between different models of dark energy even if the value of the matter density is not accurately known. For DE with an unevolving equation of state, a positive slope of $Om(z)$ is suggestive of phantom ($w<-1$) while a negative slope indicates quintessence ($w>-1$). The second diagnostic—acceleration probe $\overline{q}$—is the mean value of the deceleration parameter over a small redshift range. It can be used to determine the cosmological redshift at which the universe began to accelerate, again without reference to the current value of the matter density. We apply the $Om$ and $\overline{q}$ diagnostics to the Union data set of type Ia supernovae combined with recent data from the cosmic microwave background (Wilkinson Microwave Anisotropy Probe 5) and baryon acoustic oscillations.

We adopt methods that are well-known in statistical physics to the problem of stochastic inflation. The effective power spectrum for the classical, stochastic long-wavelength fluctuations is calculated for free scalar fields in a de Sitter background. For a smooth separation into long and short wavelengths, we identify an infrared divergence of the effective power spectrum, which has its correspondence in statistical physics in the phenomenon of dimensional reduction. The inflationary dynamics pushes the affected scales exponentially fast to large superhorizon scales, and establishes scale-invariant behavior for smaller scales (for massless fields). In the limit of a sharp separation of wavelengths, the scale of the infrared divergence is pushed to infinity.

We present a methodology based on pointlike Lambertian sources that enables one to perform a reliable and comprehensive estimate of the overall thermally induced acceleration of the Pioneer 10 and 11 spacecraft. We show, by developing a sensitivity analysis of the several parameters of the model, that one may achieve a valuable insight into the possible thermal origin of the so-called Pioneer anomaly.

We study nonaxisymmetric collision of two black holes (BHs) with a high velocity $v=|d{x}^i/d{x}^0|=0.6c–0.9c$ at infinity, where $x^{\mu }$ denotes four-dimensional coordinates. We prepare two boosted BHs for the initial condition which is different from that computed by a simple moving-puncture approach. By extrapolation of the numerical results, we find that the impact parameter has to be smaller than $\approx 2.5G{M}_0/c^2$ for formation of a BH in the collision for $v\to c$, where $M_0{c}^2$ is the initial total Arnowitt-Deser-Misner energy of the system. For the critical value of the impact parameter, 20%–30% of mass energy and 60%–70% of angular momentum are dissipated by gravitational radiation for $v=0.6c–0.9c$.

An $SO(5)\times U(1)$ gauge-Higgs unification model in the Randall-Sundrum warped space with top and bottom quarks is constructed. Additional fermions on the Planck brane make exotic particles heavy by effectively changing boundary conditions of bulk fermions from those determined by orbifold conditions. Gauge couplings of a top quark multiplet trigger electroweak symmetry breaking by the Hosotani mechanism, simultaneously giving a top quark the observed mass. The bottom quark mass is generated by the combination of brane interactions and the Hosotani mechanism, where only one ratio of brane masses is relevant when the scale of brane masses is much larger than the Kaluza-Klein scale ($\sim 1.5\mathrm{TeV}$). The Higgs mass is predicted to be 49.9 (53.5) GeV for the warp factor ${10}^{15}$ (${10}^{17}$). The Wilson line phase turns out $\frac{1}{2}\pi$ and the Higgs couplings to $W$ and $Z$ vanish so that the LEP2 bound for the Higgs mass is evaded. In the flat spacetime limit the electroweak symmetry is unbroken.

We show that the Mellin summation technique (MST) is a well-defined and useful tool to compute loop integrals at finite temperature in the imaginary-time formulation of thermal field theory, especially when interested in the infrared limit of such integrals. The method makes use of the Feynman parametrization which has been claimed to have problems when the analytical continuation from discrete to arbitrary complex values of the Matsubara frequency is performed. We show that without the use of the MST, such problems are not intrinsic to the Feynman parametrization but instead, they arise as a result of (a) not implementing the periodicity brought about by the possible values taken by the discrete Matsubara frequencies before the analytical continuation is made and (b) to the changing of the original domain of the Feynman parameter integration, which seemingly simplifies the expression but in practice introduces a spurious end point singularity. Using the MST, there are no problems related to the implementation of the periodicity but instead, care has to be taken when the sum of denominators of the original amplitude vanishes. We apply the method to the computation of loop integrals appearing when the effects of external weak magnetic fields on the propagation of scalar particles is considered.

CERN LHC provides a good experimental platform to perturbatively probe the fundamental gravity scale up to several TeV, with the precise value depending on the number of extra dimensions. The leading experimental signal of the graviton at the LHC is from the process $pp\to \mathrm{\text{jet}}+{\mathrm{E̸}}_T$, where ${\mathrm{E̸}}_T$ stands for the transverse missing energy. A detailed discussion on the hadronic production of the real graviton through hard subprocesses: $q\overline{q}\to G+g$, $g+q\to G+q$, and $g+g\to G+g$ have been studied within the quantum gravity theory with large extra dimensions. The main theoretical uncertainties together with the dominant standard model background to these processes, e.g. $q\overline{q}\to Z^0+g$ and $g+q\to Z^0+q$ with $Z^0$ further decaying into neutrinos, have also been discussed. It is found that only in a certain jet energy region and with a certain number of extra dimensions can the quantum gravity signal be distinguished from the background, which inversely lead to the effective scale $M_D$ to be probed up to $(8.8\pm 0.9)\mathrm{TeV}$ for two extra dimensions and $(5.9\pm 0.5)\mathrm{TeV}$ for four extra dimensions with sufficient integrated luminosity, e.g. $100{\mathrm{fb}}^{-1}$, at CERN LHC.