The direct detection of gravitational waves will provide valuable astrophysical information about many celestial objects. The SCHENBERG has already undergone its first test run. It is expected to have its first scientific run soon. In this work a new data analysis approach is presented, called the method of independent bars, which can be used with SCHENBERG’s data. We test this method through the simulation of the detection of gravitational waves. With this method we find the source’s direction without the need to have all six transducers operational. Also, we show that the method is a generalization of another one, already described in the literature, known as the mode channels method.

We complete the list of one-loop renormalization group equations and matching conditions relevant for the computation of the electroweak precision parameters $S$ and $T$ in the three site Higgsless model. We obtain one-loop formulas for $S$ and $T$ expressed in terms of physical observables such as the Kaluza-Klein (KK) gauge boson mass $M_{W^{\prime }}$, the KK fermion mass $M$, and the KK gauge boson ($W^{\prime }$) couplings with light quarks and leptons $g_{W^{\prime }ff}$. It is shown that these physical observables, $M_{W^{\prime }}$, $M$, and $g_{W^{\prime }ff}$ are severely constrained by the electroweak precision data. Unlike the tree level analysis on the ideally delocalized fermion, we find that perfect fermiophobity of $W^{\prime }$ is ruled out by the precision data. We also study the cutoff dependence of our analysis. Although the model is nonrenormalizable, the dependence on the cutoff parameter $\Lambda$ is shown to be nonsignificant.

In compressed supersymmetry, a light top squark naturally mediates efficient neutralino pair annihilation to govern the thermal relic abundance of dark matter. I study the CERN LHC signal of same-sign leptonic top-quark decays from gluino and squark production, which follows from gluino decays to top plus stop followed by the stop decaying to a charm quark and the LSP in these models. Measurements of the numbers of jets with heavy-flavor tags in the same-sign lepton events can be used to confirm the origin of the signal. Summed transverse momentum observables provide an estimate of an effective superpartner mass, which is correlated with the gluino mass. Measurements of invariant mass endpoints from the visible products of gluino decays do not allow direct determination of superpartner masses, but can place constraints on them, including lower bounds on the gluino mass as a function of the top-squark mass.

What if only a light Higgs boson is discovered at the CERN LHC? Conventional wisdom tells us that the scattering of longitudinal weak gauge bosons would not grow strong at high energies. However, this is generally not true. In some composite models or general two-Higgs-doublet models, the presence of a light Higgs boson does not guarantee complete unitarization of the $WW$ scattering. After partial unitarization by the light Higgs boson, the $WW$ scattering becomes strongly interacting until it hits one or more heavier Higgs bosons or other strong dynamics. We analyze how LHC experiments can reveal this interesting possibility of partially strong $WW$ scattering.

In integrable field theories the S-matrix is usually a product of a relatively simple matrix and a complicated scalar factor. We make an observation that in many relativistic integrable field theories the scalar factor can be expressed as a convolution of simple kernels appearing in the nested levels of the nested Bethe ansatz. We formulate a proposal, up to some discrete ambiguities, how to reconstruct the scalar factor from the nested Bethe equations and check it for several relativistic integrable field theories. We then apply this proposal to the AdS asymptotic Bethe ansatz and recover the dressing factor in the integral representation of Dorey, Hofman, and Maldacena.

We study the shear mode in the gauge/gravity correspondence at finite temperature. First, we confirm the general formula for the shear viscosity in an arbitrary background metric which includes a black hole in the fifth dimension. We then derive a general formula for the shear mode relaxation time which appears in the theory of relativistic dissipative fluid dynamics; it agrees with known expressions in the limit of conformal fields. These results may be useful in relativistic viscous fluid descriptions of high energy nuclear collisions at RHIC and LHC.

We discuss the cosmological implications and the holographic dual theory of the 7D Randall-Sundrum gravitational setup. Adding generic matter in the bulk on the 7D gravity side, we study the cosmological evolution inferred by the nonvanishing value of the brane-bulk energy exchange parameter. This analysis is achieved in detail for specific assumptions on the internal space evolution, including analytical considerations and numerical results. The dual theory is then constructed, making use of the holographic renormalization procedure. The resulting renormalized 6D conformal field theory is anomalous and coupled to 6D gravity plus higher order corrections. The critical point analysis on the brane is performed. Finally, we sketch a comparison between the two dual descriptions. We moreover generalize the Ads/CFT dual theory to the nonconformal and interacting case, relating the energy exchange parameter of the bulk gravity description to the new interactions between hidden and visible sectors.

Using the parent Lagrangian method together with a dimensional reduction from $D$ to $(D-1)$ dimensions, we construct dual theories for massive spin two fields in arbitrary dimensions in terms of a mixed symmetry tensor $T_{A[A_1{A}_2\dots A_{D-2}]}$. Our starting point is the well-studied massless parent action in dimension $D$. The resulting massive Stueckelberg-like parent actions in $(D-1)$ dimensions inherit all the gauge symmetries of the original massless action and can be gauge fixed in two alternative ways, yielding the possibility of having a parent action with either a symmetric or a nonsymmetric Fierz-Pauli field $e_{AB}$. Even though the dual sector in terms of the standard spin two field includes only the symmetrical part $e_{\{AB\}}$ in both cases, these two possibilities yield different results in terms of the alternative dual field $T_{A[A_1{A}_2\dots A_{D-2}]}$. In particular, the nonsymmetric case reproduces the Freund-Curtright action as the dual to the massive spin two field action in four dimensions.

In a previous paper [Phys. Rev. D77, 065002 (2008)], we showed how the minimal walking technicolor model can provide a composite dark matter candidate, by forming bound states between a $-2$ electrically charged techniparticle and a ${}^4\mathrm{He}^{++}$. We studied the properties of these techni-O-helium $t\mathrm{OHe}$ “atoms,” which behave as warmer dark matter rather than cold. In this paper, we extend our work on several different aspects. We study the possibility of a mixed scenario where both $t\mathrm{OHe}$ and bound states between $+2$ and $-2$ electrically charged techniparticles coexist in the dark matter density. We argue that these newly proposed bound states are solely made of techniparticles, although they behave as weakly interacting massive particles, due to their large elastic cross section with nuclei, can only account for a small percentage of the dark matter density. Therefore, we conclude that within the minimal walking technicolor model, composite dark matter should be mostly composed of $t\mathrm{OHe}$. Moreover, in this paper, we put cosmological bounds in the masses of the techniparticles, if they compose the dark matter density. Finally, we propose within this setup, a possible explanation of the discrepancy between the DAMA/NaI and DAMA/LIBRA findings and the negative results of CDMS and other direct dark matter searches that imply nuclear recoil measurement, which should accompany ionization.

The fluctuation determinant, the preexponential factor for the instanton transition, has been computed several years ago in the Abelian Higgs model, using a method based on integrating the Euclidean Green’s function. A more elegant method for computing functional determinants, using the Gel’fand-Yaglom theorem, has been applied recently to a variety of systems. This method runs into difficulties if the background field has nontrivial topology, as is the case for the instanton in the Abelian Higgs model. A shift in the effective centrifugal barriers makes the $s$-wave contribution infinite, an infinity that is compensated by the summation over the other partial waves. This requires some modifications of the Gel’fand-Yaglom method which are the main subject of this work. We present here both the Green’s function and the Gel’fand-Yaglom method and compare the numerical results in detail.

We perform a symmetry analysis of modified Brans-Dicke cosmological equations and present exact solutions. We discuss how the solutions may help to build models of cosmology where, for the early universe, the expansion is linear and the equation of state just changes the expansion velocity but not the linearity. For the late universe the expansion is exponential and the effect of the equation of state on the rate of expansion is just to change the constant Hubble parameter.

Gravitational theories do not admit gauge invariant local operators. We study the limits under which there exists a quasilocal description for a class of nonlocal gravitational observables where a sum over worldlines plays the role of the Wilson line for gauge theory observables. We study nonlocal corrections to the local description and circumstances where these corrections become large. We find that these operators are quasilocal in flat space and anti-de Sitter, but fail to be quasilocal in de Sitter space.

We construct black hole solutions to three-dimensional Einstein-Maxwell theory with both gravitational and electromagnetic Chern-Simons terms. These intrinsically rotating solutions are geodesically complete, and causally regular within a certain parameter range. Their mass, angular momentum and entropy are found to satisfy the first law of black hole thermodynamics. These Chern-Simons black holes admit a four-parameter local isometry algebra, which generically is $sl(2,R)\times R$, and may be generated from the corresponding vacua by local coordinate transformations.

We study static solutions of the Tolman-Oppenheimer-Volkoff equations for spherically symmetric objects (stars) living in a space filled with the Chaplygin gas. Two cases are considered. In the normal case, all solutions (excluding the de Sitter one) realize a three-dimensional spheroidal geometry because the radial coordinate achieves a maximal value (the “equator”). After crossing the equator, three scenarios are possible: a closed spheroid having a Schwarzschild-type singularity with infinite blueshift at the “south pole”, a regular spheroid, and a truncated spheroid having a scalar curvature singularity at a finite value of the radial coordinate. The second case arises when the modulus of the pressure exceeds the energy density (the phantom Chaplygin gas). There is no more equator and all solutions have the geometry of a truncated spheroid with the same type of singularity. We also consider static spherically symmetric configurations existing in a universe filled with only the phantom Chaplygin gas. In this case, two classes of solutions exist: truncated spheroids and solutions of the wormhole type with a throat. However, the latter are not asymptotically flat and possess curvature singularities at finite values of the radial coordinate. Thus, they may not be used as models of observable compact astrophysical objects.

Nonaxisymmetric oscillations of rapidly rotating relativistic stars are studied using the Cowling approximation. The oscillation spectra have been estimated by Fourier transforming the evolution equations describing the perturbations. This is the first study of its kind and provides information on the effect of fast rotation on the oscillation spectra while it offers the possibility of studying the complete problem by including space-time perturbations. Our study includes both axisymmetric and nonaxisymmetric perturbations and provides limits for the onset of the secular bar mode rotational instability. We also present approximate formulas for the dependence of the oscillation spectrum from rotation. The results suggest that it is possible to extract the relativistic star’s parameters from the observed gravitational wave spectrum.

We calculate the equation of state of a gas of strings at high density in a large toroidal universe and use it to determine the cosmological evolution of background metric and dilaton fields in the entire large radius Hagedorn regime, $(\ln S{)}^{1/d}\ll R\ll S^{1/d}$ (with $S$ the total entropy). The pressure in this regime is not vanishing but of $\mathcal{O}(1)$, while the equation of state is proportional to volume, which makes our solutions significantly different from previously published approximate solutions. For example, we are able to calculate the duration of the high-density Hagedorn phase, which increases exponentially with increasing entropy, $S$. We go on to discuss the difficulties of the scenario, quantifying the problems of establishing thermal equilibrium and producing a large but not too weakly coupled universe.

The $\mathbf{f}(R)$ gravity field equations are derived as an equation of state of local space-time thermodynamics. Jacobson’s arguments are nontrivially extended, by means of a more general definition of local entropy, for which Wald’s definition of dynamic black hole entropy is used, as well as the concept of an effective Newton constant for graviton exchange, which recently appeared in the literature.

We develop techniques to determine the mass scale of invisible particles pair-produced at hadron colliders. We employ the constrained mass variable $m_{2C}$, which provides an event-by-event lower bound to the mass scale given a mass difference. We complement this variable with a new variable $m_{2C,UB}$ which provides an additional upper bound to the mass scale and demonstrate its utility with a realistic case study of a supersymmetry model. These variables together effectively quantify the “kink” in the function $\mathtt{m}\mathtt{a}\mathtt{x}$ $m_{T2}$ which has been proposed as a mass-determination technique for collider-produced dark matter. An important advantage of the $m_{2C}$ method is that it does not rely simply on the position at the end point, but it uses the additional information contained in events which lie far from the end point. We found the mass by comparing the $\mathtt{H}\mathtt{E}\mathtt{R}\mathtt{W}\mathtt{I}\mathtt{G}$ generated $m_{2C}$ distribution to ideal distributions for different masses. We find that for the case studied, with $100{\mathrm{fb}}^{-1}$ of integrated luminosity (about 400 signal events), the invisible particle’s mass can be measured to a precision of 4.1 GeV. We conclude that this technique’s precision and accuracy is as good as, if not better than, the best known techniques for invisible-particle mass determination at hadron colliders.

In the framework of the littlest Higgs model with $T$ parity (LHT), we study the production processes of $T$-even ($T_{+}$) and $T$-odd ($T_{-}$) partners of the top quark at the Large Hadron Collider (LHC). We show that the signal events can be distinguished from the standard model backgrounds, and that information about mass and mixing parameters of the top partners can be measured with relatively good accuracies. With the measurements of these parameters, we show that a nontrivial test of the LHT can be performed. We also discuss a possibility to reconstruct the thermal relic density of the lightest $T$-odd particle $A_H$ using the LHC results and show that the scenario where $A_H$ becomes dark matter may be checked.

Suggested holographic duals of QCD, based on AdS/CFT duality, predict that one should be able to vary the scales of color confinement and chiral-symmetry breaking independently. Furthermore they suggest that such independent variation of scales can be achieved by the inclusion of extra 4-fermion interactions in QCD. We simulate lattice QCD with such extra 4-fermion terms at finite temperatures and show that for strong enough 4-fermion couplings the deconfinement transition occurs at a lower temperature than the chiral-symmetry restoration transition. Moreover the separation of these transitions depends on the size of the 4-fermion coupling, confirming the predictions from the proposed holographic dual of QCD. We use simpler 4-fermion interactions than those suggested by these dual theories to facilitate our simulations. This is because we believe that the physics we wish to study should be insensitive to the precise form of these interactions.