In the context of loop quantum cosmology, we parametrize the lattice refinement by a parameter, $A$, and the matter Hamiltonian by a parameter, $\delta$. We then solve the Hamiltonian constraint for both a self-adjoint and a non-self-adjoint Hamiltonian operator. Demanding that the solutions for the wave functions obey certain physical restrictions, we impose constraints on the two-dimensional, $(A,\delta )$, parameter space, thereby restricting the types of matter content that can be supported by a particular lattice refinement model.

In order to improve the phasing of the comparable-mass waveform as we approach the last stable orbit for a system, various resummation methods have been used to improve the standard post-Newtonian waveforms. In this work we present a new family of templates for the detection of gravitational waves from the inspiral of two comparable-mass black hole binaries. These new adiabatic templates are based on reexpressing the derivative of the binding energy and the gravitational wave flux functions in terms of shifted Chebyshev polynomials. The Chebyshev polynomials are a useful tool in numerical methods as they display the fastest convergence of any of the orthogonal polynomials. In this case they are also particularly useful as they eliminate one of the features that plagues the post-Newtonian expansion. The Chebyshev binding energy now has information at all post-Newtonian orders, compared to the post-Newtonian templates which only have information at full integer orders. In this work, we compare both the post-Newtonian and Chebyshev templates against a fiducially exact waveform. This waveform is constructed from a hybrid method of using the test-mass results combined with the mass dependent parts of the post-Newtonian expansions for the binding energy and flux functions. Our results show that the Chebyshev templates achieve extremely high fitting factors at all post-Newtonian orders and provide excellent parameter extraction. We also show that this new template family has a faster Cauchy convergence, gives a better prediction of the position of the last stable orbit and in general recovers higher Signal-to-Noise ratios than the post-Newtonian templates.

We revisit the problem of defining nonminimal gravity in the first order formalism. Specializing to scalar-tensor theories, which may be disguised as “higher-derivative” models with the gravitational Lagrangians that depend only on the Ricci scalar, we show how to recast these theories as Palatini-like gravities. The correct formulation utilizes the Lagrange multiplier method, which preserves the canonical structure of the theory, and yields the conventional metric scalar-tensor gravity. We explain the discrepancies between the naïve Palatini and the Lagrange multiplier approach, showing that the naïve Palatini approach really swaps the theory for another. The differences disappear only in the limit of ordinary general relativity, where an accidental redundancy ensures that the naïve Palatini approach works there. We outline the correct decoupling limits and the strong coupling regimes. As a corollary we find that the so-called “modified source gravity” models suffer from strong coupling problems at very low scales, and hence cannot be a realistic approximation of our universe. We also comment on a method to decouple the extra scalar using the chameleon mechanism.

The curvaton in an intermediate inflationary universe model is studied. This study has allowed us to find some interesting constraints on different parameters that appear in the model.

It has long been known that gravitational lensing, primarily via magnification bias, modifies the observed galaxy (or quasar) clustering. Such discussions have largely focused on the 2D angular correlation function. Here and in paper II [L. Hui, E. Gaztañaga, and M. LoVerde, arXiv:0710.4191] we explore how magnification bias distorts the 3D correlation function and power spectrum, as first considered by Matsubara [Astrophys. J. Lett. 537, L77 (2000).]. The interesting point is that the distortion is anisotropic. Magnification bias in general preferentially enhances the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. For instance, at a LOS separation of $\sim 100\mathrm{Mpc}/\mathrm{h}$, where the intrinsic galaxy-galaxy correlation is rather weak, the observed correlation can be enhanced by lensing by a factor of a few, even at a modest redshift of $z\sim 0.35$. This effect presents an interesting opportunity as well as a challenge. The opportunity: this lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification, and magnification-magnification correlations, without measuring galaxy shapes. The anisotropy is distinguishable from the well-known distortion due to peculiar motions, as will be discussed in paper II. The challenge: the magnification distortion of the galaxy correlation must be accounted for in interpreting data as precision improves. For instance, the $\sim 100\mathrm{Mpc}/\mathrm{h}$ baryon acoustic oscillation scale in the correlation function is shifted by up to $\sim 3\%$ in the LOS orientation, and up to $\sim 0.6\%$ in the monopole, depending on the galaxy bias, redshift, and number count slope. The corresponding shifts in the inferred Hubble parameter and angular diameter distance, if ignored, could significantly bias measurements of the dark energy equation of state. Lastly, magnification distortion offers a plausible explanation for the well-known excess correlations seen in pencil beam surveys.

We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, which can be entirely described using 4D effective field theory. The mechanism, based on first producing entropic perturbations and then converting them to curvature perturbations, can be naturally incorporated in cyclic and ekpyrotic models in which the big bang is modeled as a brane collision, as well as other types of cosmological models with a pre-big bang phase. We show that the correct perturbation amplitude can be obtained and that the spectral tilt $n_s$ tends to range from slightly blue to red, with $0.97<n_s<1.02$ for the simplest models, a range compatible with current observations but shifted by a few percent towards the blue compared to the prediction of the simplest, large-field inflationary models.

The network of resonant bar detectors of gravitational waves resumed coordinated observations within the International Gravitational Event Collaboration (IGEC-2). Four detectors are taking part in this Collaboration: ALLEGRO, AURIGA, EXPLORER and NAUTILUS. We present here the results of the search for gravitational wave bursts over 6 months during 2005, when IGEC-2 was the only gravitational wave observatory in operation. The implemented network data analysis is based on a time coincidence search among AURIGA, EXPLORER and NAUTILUS; ALLEGRO data was reserved for follow-up studies. The network amplitude sensitivity to bursts improved by a factor $\approx 3$ over the 1997-2000 IGEC observations; the wider sensitive band also allowed the analysis to be tuned over a larger class of waveforms. Given the higher single-detector duty factors, the analysis was based on threefold coincidence, to ensure the identification of any single candidate of gravitational waves with high statistical confidence. The false detection rate was as low as 1 per century. No candidates were found.

We construct a conserved electromagnetic current for two-boson systems in finite mass boson exchange models within light-front dynamics. For that purpose, we use a quasipotential reduction to perform the three-dimensional light-front projection of the 4-dimensional current operator. The electromagnetic current operator acting on the valence component of bound and scattering states can be perturbatively calculated in the quasipotential expansion, in correspondence with a truncation of the Fock space. The divergence of the proposed current operator satisfies a Ward-Takahashi identity at any given order of the quasipotential expansion. Also shown is the relation between the three-dimensional light-front reduction of the field-theoretic Bethe-Salpeter amplitudes and current for bound and scattering states with the 4-dimensional ones. The matrix elements of the 4-dimensional current operator can be fully recovered from the corresponding light-front ones. In one test case the theoretical framework is realized explicitly.

In this work we examine the fat-link irrelevant clover (FLIC) overlap quark propagator and the gluon propagator on both dynamical and quenched lattices. The tadpole-improved Luscher-Weisz gauge action is used in both cases. The dynamical gauge fields use the FLIC fermion action for the sea quark contribution. We observe that the presence of sea quarks causes a suppression of the mass function, quark renormalization function, and gluon dressing function in the infrared. The ultraviolet physics is unaffected.

We discuss properties of $1^{-+}$ exotic mesons within the framework of the QCD field-theoretic approach. We estimate the mass of the lowest-lying $1^{-+}$ exotic meson using renormalization-improved QCD sum rules, and find that the mass lies around $1.26\pm 0.15\mathrm{GeV}$, in good agreement with the ${\pi }_1(1400)$ data. This state should be expected in QCD. We find that the mass for the lowest-lying strange $1^{-+}$ meson is $1.31\pm 0.19\mathrm{GeV}$. Our result hints that the $K^{*}(1410)$ may be the lowest-lying $1^{-+}$ nonet state.

Scalar-tensor theories of gravity can be formulated in different frames, most notably, the Einstein and the Jordan one. While some debate still persists in the literature on the physical status of the different frames, a frame transformation in scalar-tensor theories amounts to a local redefinition of the metric, and then should not affect physical results. We analyze the issue in a cosmological context. In particular, we define all the relevant observables (redshift, distances, cross sections, …) in terms of frame-independent quantities. Then, we give a frame-independent formulation of the Boltzmann equation, and outline its use in relevant examples such as particle freeze-out and the evolution of the cosmic microwave background photon distribution function. Finally, we derive the gravitational equations for the frame-independent quantities at first order in perturbation theory. From a practical point of view, the present approach allows the simultaneous implementation of the good aspects of the two frames in a clear and straightforward way.

In the lattice work by Miller and in the work by Zwanziger a linear growth of the trace anomaly for high temperatures was found in pure SU(2) and SU(3) Yang-Mills theories. While future numerical work is needed to confirm or to rule out the linear growth, the aforementioned results point to the remarkable property that the corresponding systems are strongly interacting even at high temperatures. We show that within an analytical approach to Yang-Mills thermodynamics this linear rise is obtained and is directly connected to the presence of a temperature-dependent ground state, which describes (part of) the nonperturbative nature of the Yang-Mills system. Our predictions are in approximate agreement with Miller and Zwanziger.

Recently, the relation between Hawking radiation and gravitational anomalies has been used to estimate the flux of Hawking radiation for a large class of black objects. In this paper, we extend the formalism, originally proposed by Robinson and Wilczek, to the Hawking radiation of vector particles (photons). It is explicitly shown, with the Hamiltonian formalism, that the theory of an electromagnetic field on $d$-dimensional spherical black holes reduces to one of an infinite number of massive complex scalar fields on 2-dimensional spacetime, for which the usual anomaly-cancellation method is available. It is found that the total energy emitted from the horizon for the electromagnetic field is just $(d-2)$ times that for a scalar field. The results support the picture that Hawking radiation can be regarded as an anomaly eliminator on horizons. Possible extensions and applications of the analysis are discussed.

We analyze the charge-parity ($CP$) asymmetry in the charged Higgs boson decays to chargino-neutralino pairs, $H^{\pm }\to {\chi }_i^{\pm }{\chi }_j^0$, $i=1$, 2, $j=1,\dots ,4$. We show first that these modes have a large branching ratio for $m_{H^{\pm }}\gtrsim 600\mathrm{GeV}$. We use Cutkosky rules to obtain the analytical formulas needed for the evaluation of the asymmetry under consideration. We then calculate the $CP$ asymmetry in chargino-neutralino decays by including supersymmetric mass bounds, as well as constraints from $b\to s\gamma$, $(g-2{)}_{\mu }$, $\Delta \rho$ and electric dipole moments. Finally, we discuss observability of the asymmetry at the LHC by calculating the number of required charged Higgs events to observe the asymmetry for each decay channel. We show that the inclusion of constraints considerably reduces the projected $CP$ asymmetry, and that the optimal channel for observing the asymmetry is $H^{\pm }\to {\chi }_1^{\pm }{\chi }_2^0$.

In the minimal supersymmetric standard model, neutralinos lighter than 50 GeV are compatible with all accelerator, precision, and cosmological bounds. Such neutralinos might constitute a relevant decay channel for the Higgs boson, modifying its expected signatures at hadron colliders. We study the branching ratio $h\to \chi \chi$ and determine the region in the supersymmetric parameter space where it is significant. We have found that, in fact, the Higgs may dominantly decay into neutralino pairs. Besides, as a result of this new channel, the branching ratio into visible modes, such as $h\to \gamma \gamma$, gets suppressed.

The cross section of the process $e^{+}{e}^{-}\to K^{+}{K}^{-}$ was measured in the energy range $\sqrt{s}=1.04–1.38\mathrm{GeV}$ in the SND experiment at the VEPP-2M $e^{+}{e}^{-}$ collider. The measured cross section is described by the model of vector meson dominance with contributions from the light vector mesons $\rho$, $\omega$, $\varphi$ and their lowest excitations. The mean statistical accuracy of the measurement is 4.4%, and the systematic uncertainty is 5.2%.

Branching fraction measurements of charmless $B^0\to K^{*0}{h}_1^{+}{h}_2^{-}$ ($h_{1,2}=K$, $\pi$) decays are presented, using a data sample of $383\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$-meson factory at SLAC. The results are $\mathcal{B}(B^0\to K^{*0}{K}^{+}{K}^{-})=(27.5\pm 1.3\pm 2.2)\times {10}^{-6}$, $\mathcal{B}(B^0\to K^{*0}{\pi }^{+}{K}^{-})=(4.6\pm 1.1\pm 0.8)\times {10}^{-6}$, and $\mathcal{B}(B^0\to K^{*0}{\pi }^{+}{\pi }^{-})=(54.5\pm 2.9\pm 4.3)\times {10}^{-6}$. The first errors quoted are statistical and the second are systematic. An upper limit is set for $\mathcal{B}(B^0\to K^{*0}{K}^{+}{\pi }^{-})<2.2\times {10}^{-6}$ at 90% confidence level. We also present measurements of $CP$-violating asymmetries for the observed decays.

We use the AdS/CFT correspondence to compute a conductivity associated with massive $\mathcal{N}=2$ supersymmetric hypermultiplet fields at finite baryon density, propagating through an $\mathcal{N}=4$ supersymmetric $SU(N_c)$ Yang-Mills plasma in the large $N_c$, large ’t Hooft coupling limit. We do so by introducing external electric and magnetic fields coupled to baryon number and computing the resulting induced current, from which we extract the conductivity tensor. At large hypermultiplet mass we compute the drag force on the charge carriers. We also compute the product of the drag coefficient with the kinetic mass, and find that the answer is unchanged from the zero-density case. The gravitational dual is a probe D7-brane, with a nontrivial world volume gauge field configuration, in an AdS-Schwarzschild background. We identify an effective horizon on the D7-brane world volume analogous to the world sheet horizon observed for strings moving in the same background. We generalize our results to a class of theories described by probe D-branes in various backgrounds.

It has recently been speculated that the end state of a collapsing universe is a tachyonic big crunch. The time reversal of this process would be the emergence of an expanding universe from a tachyonic big bang. In this framework, we study the emergence of cosmological fluctuations. In particular, we compare the amplitude of the perturbations at the end of the tachyon phase with what would be obtained assuming the usual vacuum initial conditions. We find that cosmological fluctuations emerge in a thermal state. We comment on the relation to the trans-Planckian problem of inflationary cosmology.