We discuss the effect of quantum stress tensor fluctuations in de Sitter spacetime upon the expansion of a congruence of timelike geodesics. We treat a model in which the expansion fluctuations begin on a given hypersurface in de Sitter spacetime, and find that this effect tends to grow, in contrast to the situation in flat spacetime. This growth potentially leads to observable consequences in inflationary cosmology in the form of density perturbations which depend upon the duration of the inflationary period. In the context of our model, the effect may be used to place upper bounds on this duration.

Several types of new physics scenarios are represented by contactlike effective interactions. An example is the exchange of nonstandard quanta of very large mass scales, beyond the kinematical limit for direct production set by the available collider energy. This kind of interactions can be revealed only through deviations of observables from the standard model predictions. If such deviations were observed, the relevant source should be identified among the possible models that could explain them. Here, we assess the expected “identification reach” on the ADD model of gravity in large compactified extra dimensions, against the compositeness-inspired four-fermion contact interaction. As basic observables we take the differential cross sections for fermion-pair production at a 0.5–1 TeV electron-positron linear collider with both beams longitudinally polarized. For the four-fermion contact interaction, we assume a general linear combination of the individual models with definite chiralities, with arbitrary coupling constants. In this sense, the estimated identification reach on the ADD model can be considered as “model independent.” In the analysis, we give estimates also for the expected “discovery reaches” on the various scenarios. We emphasize the substantial role of beams polarization in enhancing the sensitivity to the contactlike interactions under consideration.

The evidence for dark matter signals a new class of particles at the TeV scale, which may manifest themselves indirectly through loop effects. In a simple model we show that these loop effects may be responsible for the enhanced muon anomalous magnetic moment, for the neutrino mass, as well as for leptogenesis in a novel way. This scenario can be verified at LHC and/or ILC experiments.

We analyze effects of the $CP$-odd soft phases in the MSSM on the pair productions of colored superpartners in $pp$ collisions at the LHC energies. We find that, among all pair-production processes, those of the scalar quarks in the first and second generations are particularly sensitive to the $CP$-odd phases, more precisely, to the phases of the gluinos and neutralinos. We compute pair-production cross sections, classify various production modes according to their dependencies on the gluino and neutralino phases, perform a detailed numerical analysis to determine individual as well as total cross sections, and give a detailed discussion of 2. electric dipole moment (EDM) bounds. We find that pair productions of first and second generation squarks serve as a viable probe of the $CP$ violation sources in the gaugino sector of the theory even if experiments cannot determine chirality, flavor and electric charge of the squarks produced.

We compute the ratio of pseudoscalar decay constants $f_K/f_{\pi }$ using domain-wall valence quarks and rooted improved Kogut-Susskind sea quarks, at a lattice spacing of $b\sim 0.125\mathrm{fm}$. By employing continuum chiral perturbation theory, we extract the Gasser-Leutwyler low-energy constant $L_5$ and extrapolate $f_K/f_{\pi }$ to the physical point. We find $f_K/f_{\pi }=1.218\pm {0.002}_{-0.024}^{+0.011}$ where the first error is statistical and the second error is an estimate of the systematic due to chiral extrapolation and fitting procedures. This value agrees within the uncertainties with the determination by the MILC collaboration, calculated using Kogut-Susskind valence quarks, suggesting that systematic errors arising from the choice of lattice valence quark are small.

We propose a physically motivated parametrization for the unpolarized generalized parton distributions. At zero value of the skewness variable, $\zeta$, the parametrization is constrained by simultaneously fitting the experimental data on both the nucleon elastic form factors and the deep inelastic structure functions. A rich phenomenology can be addressed based on this parametrization. In particular, we track the behavior of the average: (i) interparton distances as a function of the momentum fraction, $X$, (ii) $X$ as a function of the four-momentum transfer, $t$; and (iii) the intrinsic transverse momentum $k_{\perp }$ as a function of $X$. We discuss the extension of our parametrization to $\zeta \ne 0$ where additional constraints are provided by higher moments of the generalized parton distributions obtained from ab initio lattice QCD calculations.

We study the constraints on gravity scale $M_P$ in extra-dimension gravitational theory, obtained from gravity-induced processes. The obtained constraints are subdivided into strong (though not robust) and reliable (though less strong). The strong constraints can be in principle relaxed due to some broken gauge symmetries, e.g. family symmetry. The strongest constraint is given by neutrino oscillations. For different assumptions the lower bound on $M_P$ is ${10}^{15}–{10}^{18}\mathrm{GeV}$. However, it can be, in principle, reduced by broken family symmetry. More reliable bounds are due to flavor-conserved operators or those which change the flavors within one family. These bounds, obtained using the electron mass and width of $\pi \to e\nu$ decay, are $1\times {10}^5\mathrm{GeV}$ and $5\times {10}^5\mathrm{GeV}$, for these two cases, respectively.

In the standard cosmological model, magnetic fields and vorticity are generated during the radiation era via second-order density perturbations. In order to clarify the complicated physics of this second-order magnetogenesis, we use a covariant approach and present the electromagneto-dynamical equations in the nonlinear regime. We use the tight-coupling approximation to analyze Thomson and Coulomb scattering. At the zero-order limit of exact tight coupling, we show that the vorticity is zero and no magnetogenesis takes place at any nonlinear order. We show that magnetogenesis also fails at all orders if either protons or electrons have the same velocity as the radiation, and momentum transfer is neglected. Then we prove a key no-go result: at first order in the tight-coupling approximation, magnetic fields and vorticity still cannot be generated even via nonlinear effects. The tight-coupling approximation must be broken at first order, for the generation of vorticity and magnetic fields, and we derive a closed set of nonlinear evolution equations that governs this generation. We estimate that the amplitude of the magnetic field at recombination on the horizon scale is $\sim {10}^{-27}\mathrm{G}$.

We establish a connection between the quark model results and the $1/N_c$ expansion mass formula used in the description of baryon resonances. We show that a remarkable compatibility exists between the two methods.

We consider in detail the possibility that the Higgs is wholly or partially excluded from propagating into one otherwise universal extra dimension. This exclusion of the Higgs from propagating into an otherwise universal extra dimension violates tree-level Kaluza-Klein number conservation in the Yukawa interactions. As a consequence, there is inter-mode mixing between fermions. For example, zero-mode fermions mix with their associated Kaluza-Klein excitations. This is in contrast to the original universal extra dimensions scenario, in which conservation of Kaluza-Klein number prohibits such inter-mode mixing. Inter-mode mixing is especially significant for the top quark, since its mass ($171.4\pm 2.1\mathrm{GeV}$) is approximately one-half the current Tevatron mass bound ($\sim 350–400\mathrm{GeV}$) for Kaluza-Klein excitations of quarks propagating into universal extra dimensions. We compute the effects that mixing among the zero-modes and lowest-lying Kaluza-Klein excitations has on the lightest third-generation charge $2/3$ quark mass eigenvalue in the nonuniversal Higgs model with one otherwise universal extra dimension. Another consequence of the inter-mode mixing is that the Kaluza-Klein excitations of the fermions can decay to a zero-mode Higgs and a corresponding zero-mode fermion. As a result, the pair production of Kaluza-Klein excitations of the top quark would lead to two zero-mode Higgs bosons plus a zero-mode top quark/antiquark pair. We compute the cross section that the nonuniversal Higgs model contributes to Higgs production at the Large Hadron Collider. The effect is quite large: For example, the Kaluza-Klein contribution to Higgs production is comparable to or larger than the Standard Model contribution, depending on the Higgs mass, for compactification scales up to about 600 GeV.

We derive a general framework for describing semi-inclusive deep-inelastic lepton-nucleon scattering in terms of the unintegrated parton distributions and other higher-twist parton correlations. Such a framework provides a consistent approach to the calculation of inclusive and semi-inclusive cross sections including higher-twist effects. As an example, we calculate the azimuthal asymmetries to the order of $1/Q$ in semi-inclusive process with transversely polarized target. A nonvanishing single-spin asymmetry in the “triggered inclusive process” is predicted to be $1/Q$ suppressed with a part of the coefficient related to a moment of the Sivers function.

Any theory that has a global spontaneously broken symmetry will imply the existence of very light neutral bosons or massless bosons (sometimes called Majorons). For most of these models we have neutrino-Majoron couplings that appear as additional branching ratios in decays of mesons and leptons. Here we present an updated limit on the couplings between the electron, muon, and tau neutrinos and Majorons. For such we analyze the possible effects of Majoron emission in both meson and lepton decays. In the latter we also include an analysis of the muon decay spectrum. Our results are $|g_{e\alpha }{|}^2<5.5\times {10}^{-6}$, $|g_{\mu \alpha }{|}^2<4.5\times {10}^{-5}$ and $|g_{\tau \alpha }{|}^2<5.5\times {10}^{-2}$ at 90% C. L., where $\alpha =e$, $\mu$, $\tau$.

If the value of ${\theta }_{13}$ is within the reach of the upcoming generation of long-baseline experiments, T2K and NOνA, we show that a low-energy neutrino factory, with peak energy in the few GeV range, would provide a sensitive tool to explore $CP$ violation and the neutrino mass hierarchy. We consider baselines with the typical length 1000–1500 km. The unique performance of the low-energy neutrino factory is due to the rich neutrino oscillation pattern at energies between 1 and 4 GeV at baselines $\mathcal{O}(1000)\mathrm{km}$. We perform both a semianalytical study of the sensitivities and a numerical analysis to explore how well this setup can measure ${\theta }_{13}$, $CP$ violation, and determine the type of mass hierarchy and the ${\theta }_{23}$ octant. A low-energy neutrino factory provides a powerful tool to resolve ambiguities and make precise parameter determinations, for both large and fairly small values of the mixing parameter ${\theta }_{13}$.

We present the results of a search for $W^{\prime }$ boson decaying to electron-neutrino pairs in $p\overline{p}$ collisions at a center-of-mass energy of 1.96 TeV, using a data sample corresponding to $205\mathrm{p}{\mathrm{b}}^{-1}$ of integrated luminosity collected by the CDF II detector at Fermilab. We observe no evidence for this decay mode and set limits on the production cross section times branching fraction, assuming the neutrinos from $W^{\prime }$ boson decays to be light. If we assume the manifest left-right symmetric model, we exclude a $W^{\prime }$ boson with mass less than $788\mathrm{GeV}/c^2$ at the 95% confidence level.

We discuss the coherent search strategy to detect gravitational waves from inspiraling compact binaries by a network of correlated laser interferometric detectors. From the maximum likelihood ratio statistic, we obtain a coherent statistic which is slightly different from and generally better than what we obtained in our previous work. In the special case when the cross spectrum of two detectors normalized by the power spectrum density is constant, the new statistic agrees with the old one. The quantitative difference of the detection probability for a given false alarm rate is also evaluated in a simple case.

We study the evaporation of ($4+n$)-dimensional rotating black holes into scalar degrees of freedom on the brane. We calculate the corresponding absorption probabilities and cross sections obtaining analytic solutions in the low-energy regime and compare the derived analytic expressions to numerical results, with very good agreement. We then consider the high-energy regime, construct an analytic high-energy solution to the scalar-field equation by employing a new method, and calculate the absorption probability and cross section for this energy regime, finding again a very good agreement with the exact numerical results. We also determine the high-energy asymptotic value of the total cross section and compare it to the analytic results derived from the application of the geometrical optics limit.

We discuss exact solutions of a three-parameter nonminimal Einstein-Yang-Mills model, which describe the wormholes of a new type. These wormholes are considered to be supported by the SU(2)-symmetric Yang-Mills field, nonminimally coupled to gravity, the Wu-Yang ansatz for the gauge field being used. We distinguish between regular solutions, describing traversable nonminimal Wu-Yang wormholes, and black wormholes possessing one or two event horizons. The relation between the asymptotic mass of the regular traversable Wu-Yang wormhole and its throat radius is analyzed.

We examine the electromagnetic properties of Kerr–anti-de Sitter (Kerr-AdS) black holes in four and higher spacetime dimensions. Assuming that the black holes may carry a test electric charge we show that the Killing one-form which represents the difference between the timelike generators in the spacetime and in the reference background can be used as a potential one-form for the associated electromagnetic field. In four dimensions the potential one-form and the Kerr-AdS metric with properly rescaled mass parameter solve the Einstein-Maxwell equations, thereby resulting in the familiar Kerr-Newman-AdS solution. We solve the quartic equation governing the location of the event horizons of the Kerr-Newman-AdS black holes and present closed analytic expressions for the radii of the horizons. We also compute the gyromagnetic ratio for these black holes and show that it corresponds to $g=2$ just as for ordinary black holes in asymptotically flat spacetime. Next, we compute the gyromagnetic ratio for the Kerr-AdS black holes with a single angular momentum and with a test electric charge in all higher dimensions. The gyromagnetic ratio crucially depends on the dimensionless ratio of the rotation parameter to the curvature radius of the AdS background. At the critical limit, when the boundary Einstein universe is rotating at the speed of light, it tends to $g=2$ irrespective of the spacetime dimension. Finally, we consider the case of a five-dimensional Kerr-AdS black hole with two angular momenta and show that it possesses two distinct gyromagnetic ratios in accordance with its two orthogonal two-planes of rotation. In the special case of two equal angular momenta, the two gyromagnetic ratios merge into one leading to $g=4$ at the maximum angular velocities of rotation.

In this work we compute the contributions to the Higgs effective potential coming from the fermion and gauge boson sectors at the one-loop level in the context of the $SU(5)/SO(5)$ littlest Higgs (LH) model using a cutoff $\Lambda$ and including all finite parts. We consider both, the $(SU(2)\times U(1){)}_1\times (SU(2)\times U(1){)}_2$ and the $(SU(2)\times U(1){)}_1\times (SU(2)\times U(1))$ gauge group versions of the LH model. We also show that the Goldstone bosons present in the model do not contribute to the effective potential at the one-loop level. Finally, by neglecting the contribution of higher dimensional operators, we discuss the restrictions that the new one-loop contributions set on the parameter space of the LH model and the need to include higher loop corrections to the Higgs potential.

We examine the prospects for detecting $\gamma$-rays from dark matter annihilation in the six most promising dwarf spheroidal (dSph) satellite galaxies of the Milky Way. We use recently measured velocity dispersion profiles to provide a systematic investigation of the dark matter mass distribution of each galaxy, and show that the uncertainty in the $\gamma$-ray flux from mass modeling is less than a factor of $\sim 5$ for each dSph if we assume a smooth Navarro-Frenk-White (NFW) profile. We show that Ursa Minor and Draco are the most promising dSphs for $\gamma$-ray detection with GLAST and other planned observatories. For each dSph, we investigate the flux enhancement resulting from halo substructure, and show that the enhancement factor relative to a smooth halo flux cannot be greater than about 100. This enhancement depends very weakly on the lower mass cutoff scale of the substructure mass function. While the amplitude of the expected flux from each dSph depends sensitively on the dark matter model, we show that the flux ratios between the six Sphs are known to within a factor of about 10. The flux ratios are also relatively insensitive to the current theoretical range of cold dark matter halo central slopes and substructure fractions.