We study the “lepton-specific” two Higgs doublet model, in which one doublet ${\Phi }_{\ell }$ gives mass to charged leptons and the other ${\Phi }_q$ gives mass to both up- and down-type quarks. We examine the existing experimental constraints on the charged Higgs boson mass and the parameter $\tan \beta \equiv ⟨{\Phi }_q^0⟩/⟨{\Phi }_{\ell }^0⟩$. The most stringent constraints come from LEP-II direct searches and lepton flavor universality in $\tau$ decays. The former yields $M_{H^{\pm }}\ge 92.0\mathrm{GeV}$; the latter yields two allowed regions $0.61\tan \beta \mathrm{GeV}\le M_{H^{\pm }}\le 0.73\tan \beta \mathrm{GeV}$ or $M_{H^{\pm }}\ge 1.4\tan \beta \mathrm{GeV}$, and excludes parameter regions beyond the LEP-II bound for $\tan \beta \gtrsim 65$. We present the charged Higgs decay branching fractions and discuss prospects for charged Higgs discovery at the LHC in this model.

Heavy resonances appearing in the clean Drell-Yan channel may be the first new physics to be observed at the proton-proton CERN LHC. If a new resonance is discovered at the LHC as a peak in the dilepton invariant mass distribution, the characterization of its spin and couplings will proceed via measuring production rates and angular distributions of the decay products. We discuss the discrimination of the spin-1 of $Z^{\prime }$ representative models ($Z_{\mathrm{SSM}}^{\prime }$, $Z_{\psi }^{\prime }$, $Z_{\eta }^{\prime }$, $Z_{\chi }^{\prime }$, $Z_{\mathrm{LR}}^{\prime }$, and $Z_{\mathrm{ALR}}^{\prime }$) against the Randall-Sundrum graviton resonance (spin-2) and a spin-0 resonance (sneutrino) with the same mass and producing the same number of events under the observed peak. To assess the range of the $Z^{\prime }$ mass where the spin determination can be performed to a given confidence level, we focus on the angular distributions of the Drell-Yan leptons, in particular, we use as a basic observable an angular-integrated center-edge asymmetry, $A_{\mathrm{CE}}$. The spin of a heavy $Z^{\prime }$ gauge boson can be established with $A_{\mathrm{CE}}$ up to $M_{Z^{\prime }}\simeq 3.0\mathrm{TeV}$, for an integrated luminosity of $100{\mathrm{fb}}^{-1}$, or minimal number of events around 110. We also examine the distinguishability of the considered $Z^{\prime }$ models from one another, once the spin-1 has been established, using the total dilepton production cross section. With some assumption, one might be able to distinguish among these $Z^{\prime }$ models at 95% C.L. up to $M_{Z^{\prime }}\simeq 2.1\mathrm{TeV}$.

Electroweak baryogenesis in the minimal supersymmetric standard model can account for the cosmological baryon asymmetry, but only within a restricted region of the parameter space. In particular, minimal supersymmetric standard model electroweak baryogenesis requires a mostly right-handed stop that is lighter than the top quark and a standard model-like light Higgs boson. In the present work we investigate the effects of the light stop on Higgs boson production and decay. Relative to the standard model Higgs boson, we find a large enhancement of the Higgs production rate through gluon fusion and a suppression of the Higgs branching fraction into photon pairs. These modifications in the properties of the Higgs boson are directly related to the effect of the light stop on the electroweak phase transition, and are large enough that they can potentially be tested at the Tevatron and the LHC.

Dark matter candidates comprising several substates separated by a small mass gap $\Delta m$, and coupled to the standard model by (sub-)GeV force carriers, can exhibit nontrivial scattering interactions in direct-detection experiments. We analyze the secluded $\mathrm{U}(1{)}_S$-mediated weakly interacting massive particle (WIMP) scenario, and calculate the elastic and inelastic cross sections for multicomponent WIMP scattering off nuclei. We find that second-order elastic scattering, mediated by virtual excited states, provides strong sensitivity to the parameters of the model for a wide range of mass splittings, while for small $\Delta m$ the WIMP excited states have lifetimes exceeding the age of the Universe, and generically have a fractional relative abundance above 0.1%. This generates even stronger constraints for $\Delta m\lesssim 200\mathrm{keV}$ due to exothermic deexcitation events in detectors.

We study the momentum dependence of the ghost propagator and of the space and time components of the gluon propagator at equal time in pure $SU(3)$ lattice Coulomb-gauge theory carrying out a joint analysis of data collected independently at the Research Center for Nuclear Physics, Osaka and Humboldt University, Berlin. We focus on the scaling behavior of these propagators at $\beta =5.8,\dots ,6.2$ and apply a matching technique to relate the data for the different lattice cutoffs. Thereby, lattice artifacts are found to be rather strong for both instantaneous gluon propagators at a large momentum. As a byproduct we obtain the respective lattice scale dependences $a(\beta )$ for the transversal gluon and the ghost propagator which indeed run faster with $\beta$ than two-loop running, but slightly slower than what is known from the Necco-Sommer analysis of the heavy quark potential. The abnormal $a(\beta )$ dependence as determined from the instantaneous time-time gluon propagator, $D_{44}$, remains a problem, though. The role of residual gauge-fixing influencing $D_{44}$ is discussed.

We investigate the experimental capabilities required to test whether black holes destroy information. We show that an experiment capable of illuminating the information puzzle must necessarily be able to detect or manipulate macroscopic superpositions (i.e., Everett branches). Hence, it could also address the fundamental question of decoherence versus wave function collapse.

We study the spin dependence of accretion onto rotating Kerr black holes using analytic techniques. In its linear regime, angular momentum transport in MHD turbulent accretion flow involves the generation of radial magnetic field connecting plasma in a differentially rotating flow. We take a first principles approach, highlighting the constraint that limits the generation and amplification of radial magnetic fields, stemming from the transfer of energy from mechanical to magnetic form. Because the energy transferred in magnetic form is ultimately constrained by gravitational potential energy or Killing energy, the spin dependence of the latter allows us to derive spin-dependent constraints on the success of the accreting plasma to expel its angular momentum. We find an inverse relationship between this ability and black hole spin. If this radial magnetic field generation forms the basis for angular momentum transfer in accretion flows, accretion rates involving Kerr black holes are expected to be lower as the black hole spin increases in the prograde sense.

We use cosmic microwave background radiation (WMAP and ACBAR), large-scale structure (SDSS luminous red galaxies), and supernova (SNLS) data to constrain the possible contribution of cold dark matter isocurvature modes to the primordial perturbation spectrum. We consider three different admixtures with adiabatic modes in a flat $\Lambda \mathrm{CDM}$ cosmology with no tensor modes: fixed correlations with a single spectral index; general correlations with a single spectral index; and general correlations with independent spectral indices for each mode. For fixed correlations, we verify the WMAP analysis for fully uncorrelated and anticorrelated modes, while for general correlations with a single index we find a small tightening of the constraint on the fractional contribution of isocurvature modes to the observed power over earlier work. For generally correlated modes and independent spectral indices our results are quite different to previous work, needing a doubling of prior space for the isocurvature spectral index in order to explore adequately the region of high likelihood. Standard Markov-Chain Monte Carlo techniques proved to be inadequate for this particular application; instead, our results are obtained with nested sampling. We also use the Bayesian evidence, calculated simply in the nested-sampling algorithm, to compare models, finding the pure adiabatic model to be favored over all our isocurvature models. This favoring is such that the logarithm of the Bayes factor, $\ln B<-2$ for all models and $\ln B<-5$ in the cases of fully anticorrelated modes with a single spectral index (the curvaton scenario) and generally correlated modes with a single spectral index.

In this paper we consider tensor perturbations produced at a bounce phase in the presence of holonomy corrections. Here, the bounce phase and holonomy corrections originate from loop quantum cosmology. We rederive formulas for the corrections of a model with scalar field content. Background dynamics with a free scalar field and multifluid potential are considered. Because the considerations are semiclassical, effects of quantum fluctuations of the background dynamics are not taken into account. Quantum and classical backreaction effects are also neglected. To find the spectrum of the gravitational waves, both analytical approximations and numerical investigations are performed. We have found analytical solutions on superhorizontal and subhorizontal regimes and derived the corresponding tensor power spectra. Also, the occupation number $n_{\mathbf{k}}$ and the parameter ${\Omega }_{\mathrm{gw}}$ were derived in the subhorizontal limit, leading to the extremely low present value of ${\Omega }_{\mathrm{gw}}$. The final results are the numerical power spectra of the gravitational waves produced in the presence of quantum holonomy corrections. The spectrum obtained has two UV and IR branches where ${\mathcal{P}}_T\propto k^2$; however, they have different prefactors. The spectrum connecting these regions is in the form of oscillations. We have found good agreement between the numerical spectrum and the spectrum obtained from the analytical model. The obtained spectrum can be directly applied as an initial condition for the inflationary modes. Based on our results, we discuss implications on the CMB radiation, in particular, on B-type polarization.

We analyze the gravitational wave signatures of a network of metastable cosmic strings. We consider the case of cosmic string instability to breakage, with no primordial population of monopoles. This scenario is well motivated from grand unified theories and string-theoretic models with an inflationary phase below the grand unified theories/string scale. The network initially evolves according to a scaling solution, but with breakage events resulting from confined monopoles (beads) being pair produced and accelerated apart. We find these ultrarelativistic beads to be a potent source of gravitational wave bursts, detectable by initial LIGO, advanced LIGO, and LISA. Indeed, advanced LIGO could observe bursts from strings with tensions as low as $G\mu \sim {10}^{-12}$. In addition, we find that ultrarelativistic beads produce a scale-invariant stochastic background detectable by LIGO, LISA, and pulsar timing experiments. The stochastic background is scale invariant up to the Planckian frequencies. This phenomenology provides new constraints and signatures of cosmic strings that disappear long before the present day.

Many statistics available to constrain non-Gaussianity from inflation are simplest to use under the assumption that the curvature correlation functions are hierarchical. That is, if the $n$-point function is proportional to the $(n-1)$ power of the two-point function amplitude and the fluctuations are small, the probability distribution can be approximated by expanding around a Gaussian in moments. However, single-field inflation with higher derivative interactions has a second small number, the sound speed, that appears in the problem when non-Gaussianity is significant and changes the scaling of correlation functions. Here we examine the structure of correlation functions in the most general single scalar field action with higher derivatives, formalizing the conditions under which the fluctuations can be expanded around a Gaussian distribution. We comment about the special case of the Dirac-Born-Infeld action.

We study the local flux of electrons and positrons from annihilating dark matter (DM), and investigate how its spectrum depends on the choice of DM model and inhomogeneities in the DM distribution. Below a cutoff energy, the flux is expected to have a universal power-law form with an index $n\approx -2$. The cutoff energy and the behavior of the flux near the cutoff is model dependent. The dependence on the DM host halo profile may be significant at energies $E<100\mathrm{GeV}$ and leads to softening of the flux $n<-2$. There may be additional features at high energies due to the presence of local clumps of DM, especially for models in which the Sommerfeld effect boosts subhalo luminosities. In general, the flux from a nearby clump gives rise to a harder spectrum of electrons and positrons, with an index $n>-2$. Using the Via Lactea II simulation, we estimate the probability of such subhalo effects in a generic Sommerfeld-enhanced model to be at least 4%, and possibly as high as 15% if subhalos below the simulation’s resolution limit are accounted for. We discuss the consequences of these results for the interpretation of the ATIC, PAMELA, HESS, and Fermi data, as well as for future experiments.

We investigate quintessence and phantom dark-energy scenarios, in which the scalar fields evolve in nearly flat potentials and are nonminimally coupled to gravity. We show that all such models converge to a common behavior and we provide the corresponding approximate analytical expressions for $w({\Omega }_{\varphi })$ and $w(a)$. We find that nonminimal coupling leads to richer cosmological behavior compared to its minimal counterpart. In addition, comparison with baryon acoustic oscillation and the latest supernovae data reveals that agreement can be established more easily and with less strict constraints on the model parameters.

The temperature and polarization inhomogeneities of the cosmic microwave background might bear the mark of predecoupling magnetism. The parameters of a putative magnetized background are hereby estimated, for the first time, from the observed temperature autocorrelation as well as from the measured temperature-polarization cross correlation.

We correct a mistake in the literature regarding the additive lattice spacing corrections to the mixed valence-sea meson mass and discuss the consequences for mixed action extrapolation formulas.

We make a complete catalog of extended Higgs sectors involving $\mathrm{SU}(2{)}_L$ doublets and singlets, subject to natural flavor conservation. In each case we present the couplings of a light neutral $CP$-even Higgs state $h$ in terms of the model parameters, and identify which models are distinguishable in principle based on this information. We also give explicit expressions for the model parameters in terms of $h$ couplings and exhibit the behaviors of the couplings in the limit where the deviations from the standard model (SM) Higgs couplings are small. Finally, we discuss prospects for differentiation of extended Higgs models based on measurements at the LHC and International Linear Collider and identify the regions in which these experiments could detect deviations from the SM Higgs predictions.

Masses of the ground state and the orbitally and radially excited states of quark-antiquark mesons composed of light $(u,d,s)$ quarks are calculated within the framework of the relativistic quark model based on the quasipotential approach. The relativistic treatment of the light quark dynamics results in mass spectra which agree well with available experimental data for the masses of the most well-established states. The Regge trajectories for angular and radial excitations are constructed, and their linearity, parallelism, and equidistance are verified. The assignment of experimentally observed light mesons to particular Regge trajectories is based on their masses and quantum numbers.

We calculate the isoscalar axial-vector coupling constants of the $\Lambda$ hyperon using the method of QCD sum rules. A determination of these coupling constants reveals the individual contributions of the $u$, $d$, and the $s$ quarks to the spin content of $\Lambda$. Our results for the light-quark contributions are in agreement with those from experiment assuming flavor SU(3). We also find that the flavor-SU(3)-breaking effects are small and the contributions from the $u$ and the $d$ quarks to the $\Lambda$ polarization are negatively polarized as in the flavor-SU(3) limit.

We study the one-loop contribution of the down-type quark of the standard model-like fourth generation ($b^{\prime }$) on the top quark electric dipole moment. Using the known limits on the top quark electric dipole moments, we place limits on the $b^{\prime }$ mass. Then, from the estimated ratio for the masses of the fourth generation of quarks from other studies and the achieved bound from top quark electric dipole moments on $m_{b^{\prime }}$, we obtain a limit for the up-type quark of fourth generation ($t^{\prime }$) mass.

Most neutrino mass extensions of the standard electroweak model entail nonstandard interactions which, in the low-energy limit, can be parametrized in term of effective four-fermion operators ${\nu }_{\alpha }{\nu }_{\beta }\overline{f}f$. Typically of subweak strength ${ϵ}_{\alpha \beta }{G}_F$, these are characterized by dimensionless coupling parameters ${ϵ}_{\alpha \beta }$, which may be relatively sizable in a wide class of schemes. Here we focus on nonuniversal flavor-conserving couplings ($\alpha =\beta$) with electrons ($f=e$) and analyze their impact on the phenomenology of solar neutrinos. We consistently take into account their effect both at the level of propagation, where they modify the standard Mikheev-Smirnov-Wolfenstein behavior, and at the level of detection, where they affect the cross section of neutrino elastic scattering on electrons. We find limits which are comparable to other existing model-independent constraints.