We study the LHC signatures of new gauge bosons in the gauge-invariant minimal Higgsless model. It predicts an extra pair of $W_1$ and $Z_1$ bosons which can be as light as $\sim 400\mathrm{GeV}$ and play a key role in the delay of unitarity violation. We analyze the $W_1$ signals in $pp\to W_0{Z}_0{Z}_0\to jj4\ell$ and $pp\to W_0{Z}_{0}jj\to \nu 3\ell jj$ processes at the LHC, including the complete electroweak and QCD backgrounds. We reveal the complementarity between these two channels for discovering the $W_1$ boson, and demonstrate the LHC discovery potential over the full range of allowed $W_1$ mass.

We study the gluonic color-spin locked (GCSL) phase in dense two-flavor quark matter. In this phase, the color and spatial rotational symmetries are spontaneously broken down to $SO(2{)}_{\mathrm{diag}}$ with the generator being an appropriate linear combination of the color and rotational ones. The Meissner masses of gluons and the mass of the radial mode of the diquark field in the GCSL phase are calculated, and it is shown that this phase is free from the chromomagnetic and Sarma instabilities in the whole parameter region where it exists. The GCSL phase describes an anisotropic color and electromagnetic superconducting medium. Because most of the initial symmetries in this phase are spontaneously broken, it has very rich dynamics.

We have studied a holographically dual description of superconductor in $(2+1)$ dimensions in the presence of an applied magnetic field and observed that there exists a critical value of magnetic field, below which a charged condensate can form via a second-order phase transition.

Gravitational lensing affects observed cosmological correlation functions because observed images do not coincide with true source locations. We treat this universal effect in a general way here, deriving a single formula that can be used to determine to what extent this effect distorts any correlation function. We then apply the general formula to the correlation functions of galaxies, the 21-cm radiation field, and the cosmic microwave background.

We discuss models that can account for today’s dark energy. The underlying cosmological constant may be Planck scale but starts as a redundant coupling which can be eliminated by a field redefinition. The observed vacuum energy arises when the redundancy is explicitly broken, say by a nonminimal coupling to curvature. We give a recipe for constructing models, including $R+1/R$-type models, that realize this mechanism and satisfy all solar system constraints on gravity. A similar model, based on Gauss-Bonnet gravity, provides a technically natural explanation for dark energy and exhibits an interesting seesaw behavior: a large underlying cosmological constant gives rise to both low- and high-curvature solutions. Such models could be statistically favored in the string landscape.

We consider a $SU(5)\times U(1{)}_F$ grand unified theory (GUT)-flavor model in which the number of effects that determine the charged fermions Yukawa matrices is much larger than the number of observables, resulting in a hierarchical fermion spectrum with no particular regularities. The GUT-flavor symmetry is broken by flavons in the adjoint of $SU(5)$, realizing a variant of the Froggatt-Nielsen mechanism that gives rise to a large number of effective operators. By assuming a common mass for the heavy fields and universality of the fundamental Yukawa couplings, we reduce the number of free parameters to one. The observed fermion mass spectrum is reproduced thanks to selection rules that discriminate among various contributions. Bottom-tau Yukawa unification is preserved at leading order, but there is no unification for the first two families. Interestingly, $U(1{)}_F$ charges alone do not determine the hierarchy, and can only give upper bounds on the parametric suppression of the Yukawa operators.

We investigate the influence of the fourth generation of quarks on the branching ratio, the $CP$ asymmetry, and the polarization asymmetries in $B\to \rho {\ell }^{+}{\ell }^{-}$ decay. Taking $|V_{t^{\prime }d}{V}_{t^{\prime }b}|\sim 0.001$ with phase about 10°, which is consistent with the $\sin 2{\varphi }_1$ of the Cabibbo-Kobayashi-Maskawa matrix and the $B_d$ mixing parameter $\Delta m_{B_d}$, we obtain that for both $(\mu ,\tau )$ channels the branching ratio is increased and the magnitude of $CP$ asymmetry and polarization asymmetries decreased by the mass and mixing parameters of the 4th generation of quarks. These results can serve as a good tool to search for new physics effects, precisely, to search for the fourth generation of quarks $(t^{\prime },b^{\prime })$ via its indirect manifestations in loop diagrams.

We consider a higher dimensional gravity theory with a negative kinetic energy scalar field and a cosmological constant. We find that the theory admits an exact cosmological solution for the scale factor of our universe. It has the feature that the universe undergoes a continuous transition from deceleration to acceleration at some finite time. This transition time can be interpreted as that of recent acceleration of our universe.

We discuss a realization of the nonrelativistic conformal group (the Schrödinger group) as the symmetry of a spacetime. We write down a toy model in which this geometry is a solution to field equations. We discuss various issues related to nonrelativistic holography. In particular, we argue that free fermions and fermions at unitarity correspond to the same bulk theory with different choices for the near-boundary asymptotics corresponding to the source and the expectation value of one operator. We describe an extended version of nonrelativistic general coordinate invariance which is realized holographically.

Supersymmetry breakdown via gaugino condensation in heterotic string theory can lead to models with a doubly suppressed gravitino mass. A TeV-scale gravitino can emerge from a condensate as large as the grand unified scale. We analyze the properties of these models and discuss applications for particle physics and cosmology.

We study the formation of monopoles and strings in a model where $SU(3)$ is spontaneously broken to $U(2)=[SU(2)\times U(1)]/{\mathbb{Z}}_2$, and then to $U(1)$. The first symmetry breaking generates monopoles with both $SU(2)$ and $U(1)$ charges since the vacuum manifold is $\mathbb{C}{P}^2$. To study the formation of these monopoles, we explicitly describe an algorithm to detect topologically nontrivial mappings on $\mathbb{C}{P}^2$. The second symmetry breaking creates ${\mathbb{Z}}_2$ strings linking either monopole-monopole pairs or monopole-antimonopole pairs. When the strings pull the monopoles together they may create stable monopoles of charge 2 or else annihilate. We determine the length distribution of strings and the fraction of monopoles that will survive after the second symmetry breaking. Possible implications for topological defects produced from the spontaneous breaking of even larger symmetry groups, as in grand unified models, are discussed.

I consider the question of the interaction between a QCD string and the spin of a quark or an antiquark on whose worldline the string terminates. The problem is analyzed from the point of view of a string representation for the expectation value of a Wilson loop for a spin-half particle. A string representation of the super Wilson loop is obtained starting from an effective string representation of a Wilson Loop. The action obtained in this manner is invariant under a worldline supersymmetry and has a boundary term which contains the spin-string interaction. For rectangular loops the spin-string interaction vanishes and there is no spin-spin term in the resulting heavy quark potential. On the other hand if an allowance is made for the finite intrinsic thickness of the flux tube by assuming that the spin-string interaction takes place not just at the boundary of the string world sheet but extends to a distance of the order of the intrinsic thickness of the flux tube then we do obtain a spin-spin interaction which falls as the fifth power of the distance. Such a term was previously suggested by Kogut and Parisi in the context of a flux-tube model of confinement.

The most fundamental strings in high-density color superconductivity are the non-Abelian semisuperfluid strings which have color-gauge flux tubes but behave as superfluid vortices in the energetic point of view. We show that in addition to the usual translational zero modes, these vortices have normalizable orientational zero modes in the internal space, associated with the color-flavor locking symmetry broken in the presence of the strings. The interaction among two parallel non-Abelian semisuperfluid strings is derived for general relative orientational zero modes to show the universal repulsion. This implies that the previously known superfluid vortices, formed by spontaneously broken $U(1{)}_{\mathrm{B}}$, are unstable to decay. Moreover, our result proves the stability of color superconductors in the presence of external color-gauge fields.

We calculate analytically the transmission and reflection amplitudes for waves incident on a rotating black hole in $d=4$, analytically continued to asymptotically large, nearly imaginary frequency. These amplitudes determine the asymptotic resonant frequencies of the black hole, including quasinormal modes, total-transmission modes and total-reflection modes. We identify these modes with semiclassical bound states of a one-dimensional Schrödinger equation, localized along contours in the complexified $r$-plane which connect turning points of corresponding null geodesics. Each family of modes has a characteristic temperature and chemical potential. The relations between them provide hints about the microscopic description of the black hole in this asymptotic regime.

The ultimate application of Einstein’s field equations is to empirically determine the geometry of the Universe from its matter content, rather than simply assuming the Universe can be represented by a homogeneous model on all scales. Choosing a Lemaître-Tolman-Bondi model as the most convenient inhomogeneous model for the early stages of development, a data reduction procedure was recently validated using perfect test data. Here, we simulate observational uncertainties and improve the previous numerical scheme to ensure that it will be usable with real data as soon as observational surveys are sufficiently deep and complete. Two regions require special treatment—the origin and the maximum in the areal radius. To minimize numerical errors near the origin, we use a Lemaître-Tolman-Bondi series expansion to provide the initial values for integrating the differential equations. We also use an improved method to match the numerical integration to the series expansion that bridges the region near the maximum in the areal radius. Because the mass enclosed within the maximum obeys a specific relationship, we show that it is possible to correct for a fixed systematic error in either the distance scale or the redshift-space mass density, such that the integrated values are consistent with the data at the maximum.

We test the resummation techniques used in developing Padé and effective one body (EOB) waveforms for gravitational wave detection. Convergence tests show that Padé approximants of the gravitational wave energy flux do not accelerate the convergence of the standard Taylor approximants even in the test mass limit, and there is no reason why Padé transformations should help in estimating parameters better in data analysis. Moreover, adding a pole to the flux seems unnecessary in the construction of these Padé-approximated flux formulas. Padé approximants may be useful in suggesting the form of fitting formulas. We compare a 15-orbit numerical waveform of the Caltech-Cornell group to the suggested Padé waveforms of Damour et al. in the equal mass, nonspinning quasicircular case. The comparison suggests that the Padé waveforms do not agree better with the numerical waveform than the standard Taylor based waveforms. Based on this result, we design a simple EOB model by modifiying the Taylor-expanded EOB model of Buonanno et al., using the Taylor series of the flux with an unknown parameter at the fourth post-Newtonian order that we fit for. The 4PN parameter incorporates higher order effects of the radiation reaction. This simple EOB model generates a waveform having a phase difference of only 0.002 radians with the numerical waveform, much smaller than 0.04 radians the phase uncertainty in the numerical data itself. An EOB Hamiltonian can make use of a Padé transformation in its construction, but this is the only place Padé transformations seem useful.

A relation between stress-energy and motion is derived for accelerated Israel layers. The relation, for layers between two Schwarzschild manifolds, generalizes the equation of state for geodesic collapse. A set of linked layers is discussed.

Antideuterons are among the most promising galactic cosmic-ray-related targets for dark matter indirect detection. Currently only upper limits exist on the flux, but the development of new experiments, such as GAPS and AMS-02, provides exciting perspectives for a positive measurement in the near future. In this paper, we present a novel and updated calculation of both the secondary and primary $\overline{d}$ fluxes. We employ a two-zone diffusion model which successfully reproduces cosmic-ray nuclear data and the observed antiproton flux. We review the nuclear and astrophysical uncertainties and provide an up to date secondary (i.e. background) antideuteron flux. The primary (i.e. signal) contribution is calculated for generic weakly interactive massive particles (WIMPs) annihilating in the galactic halo: we explicitly consider and quantify the various sources of uncertainty in the theoretical evaluations. Propagation uncertainties, as is the case of antiprotons, are sizeable. Nevertheless, antideuterons offer an exciting target for indirect dark matter detection for low and intermediate mass WIMP dark matter. We then show the reaching capabilities of the future experiments for neutralino dark matter in a variety of supersymmetric models.

We perform a systematic study of the multiwavelength signal induced by weakly interacting massive particle (WIMP) annihilations at the Galactic Center (GC). Referring to a generic WIMP dark matter (DM) scenario and depending on astrophysical inputs, we discuss spectral and angular features and sketch correlations among signals in the different energy bands. None of the components which have been associated to the GC source Sgr ${\mathrm{A}}^{*}$, nor the diffuse emission components from the GC region, have spectral or angular features typical of a DM source. Still, data sets at all energy bands, namely, the radio, near-infrared, x-ray and gamma-ray bands, contribute to place significant constraints on the WIMP parameter space. In general, the gamma-ray energy range is not the one with the largest signal to background ratio. In the case of large magnetic fields close to the GC, x-ray data give the tightest bounds. The emission in the radio band, which is less model dependent, is very constraining as well. The recent detection by HESS of a GC gamma-ray source, and of a diffuse gamma-ray component, limits the possibility of a DM discovery with the next generation of gamma-ray telescopes, like GLAST and CTA. We find that most of the region in the parameter space accessible to these instruments is actually already excluded at other wavelengths. On the other hand, there may be still an open window to improve constraints with wide-field radio observations.

In recent years there has been growing interest in verifying the horizon-scale homogeneity of the Universe that follows from applying the Copernican principle to the observed isotropy. This program has been stimulated by the discovery that a very large void, centered near us, can explain supernova luminosity distance measurements without dark energy. It is crucial to confront such models with as wide a variety of data as possible. With this application in mind, we develop the relativistic theory of linear scalar perturbations on spherically symmetric dust (Lemaître-Tolman-Bondi) spacetimes, using the covariant $1+1+2$ formalism. We show that the evolution of perturbations is determined by a small set of new linear transfer functions. If decaying modes are ignored (to be consistent with the standard inflationary paradigm), the standard techniques of perturbation theory on homogeneous backgrounds, such as harmonic expansion, can be applied, and results closely paralleling those of familiar cosmological perturbation theory can be obtained.