We determine the static potential for a heavy quark-antiquark pair from gluodynamics in curved space-time. Our calculation is done within the framework of the gauge-invariant, path-dependent, variables formalism. The potential energy is the sum of a Yukawa and a linear potential, leading to the confinement of static charges.

We present a straightforward approach for estimating the final black hole spin of a binary black hole coalescence with arbitrary initial masses and spins. Making some simple assumptions, we estimate the final angular momentum to be the sum of the individual spins plus the orbital angular momentum of a test particle orbiting at the last stable orbit around a Kerr black hole with a spin parameter of the final black hole. The formula we obtain is able to reproduce with reasonable accuracy the results from available numerical simulations, but, more importantly, it can be used to investigate what configurations might give rise to interesting dynamics. In particular, we discuss scenarios which might give rise to a flip in the direction of the total angular momentum of the system. By studying the dependence of the final spin upon the mass ratio and initial spins, we find that our simple approach suggests that it is not possible to spin-up a black hole to extremal values through merger scenarios irrespective of the mass ratio of the objects involved.

We propose an afterglow phenomenon as a unique trace of chameleon fields in optical experiments. The vacuum interaction of a laser pulse with a magnetic field can lead to a production and subsequent trapping of chameleons in the vacuum chamber, owing to their mass dependence on the ambient matter density. Magnetically induced reconversion of the trapped chameleons into photons creates an afterglow over macroscopic timescales that can conveniently be searched for by current optical experiments. We show that the chameleon parameter range accessible to available laboratory technology is comparable to scales familiar from astrophysical stellar energy-loss arguments. We analyze quantitatively the afterglow properties for various experimental scenarios and discuss the role of potential background and systematic effects. We conclude that afterglow searches represent an ideal tool to aim at the production and detection of cosmologically relevant scalar fields in the laboratory.

In this article we study the electrical conductivity in QED using the resummed 3PI effective action. We work to 3-loop order in the effective action. We show that the resulting expression for the conductivity is explicitly gauge invariant, and that the integral equations that resum the pinching and colinear contributions are produced naturally by the formalism. All leading order terms are included, without the need for any kind of power counting arguments.

We study parameter estimation of supermassive black hole binary systems in the final stage of inspiral using the full post-Newtonian gravitational waveforms. We restrict our analysis to systems in circular orbit with negligible spins, in the mass range ${10}^8{M}_{\odot }-{10}^5{M}_{\odot }$, and compare the results with those arising from the commonly used restricted post-Newtonian approximation. The conclusions of this work are particularly important with regard to the astrophysical reach of future Laser Interferometer Space Antenna measurements. Our analysis clearly shows that modeling the inspiral with the full post-Newtonian waveform, not only extends the reach to higher mass systems, but also improves in general the parameter estimation. In particular, there are remarkable improvements in angular resolution and distance measurement for systems with a total mass higher than $5\times {10}^6{M}_{\odot }$, as well as a large improvement in the mass determination.

Nonaxisymmetric oscillations of differentially rotating stars are studied using both slow rotation and Cowling approximation. The equilibrium stellar models are relativistic polytropes where differential rotation is described by the relativistic j-constant rotation law. The oscillation spectrum is studied versus three main parameters: the stellar compactness $M/R$, the degree of differential rotation $A$, and the number of maximum couplings ${\ell }_{\max }$. It is shown that the rotational splitting of the nonaxisymmetric modes are strongly enhanced by increasing the compactness of the star and the degree of differential rotation. Finally, we investigate the relation between the fundamental quadrupole mode and the corotation band of differentially rotating stars.

The implications of a generalized Uncertainty principle on the Taub cosmological model are investigated. The model is studied in the Arnowitt-Deser-Misner reduction of the dynamics and therefore a time variable is ruled out. Such a variable is quantized in a canonical way and the only physical degree of freedom of the system (related to the universe anisotropy) is quantized by means of a modified Heisenberg algebra. The analysis is performed at both the classical and quantum level. In particular, at quantum level, the motion of wave packets is investigated. The two main results obtained are as follows: (i) The classical singularity is probabilistically suppressed. The universe exhibits a stationary behavior and the probability amplitude is peaked in a determinate region. (ii) The generalized uncertainty principle wave packets provide the right behavior in the establishment of a quasi-isotropic configuration for the universe.

We present a simplest inflationary scenario in the minimal left-right symmetric model with spontaneous $D$-parity breaking, which is a well-motivated particle physics model for neutrino masses. This leads us to connect the observed anisotropies in the cosmic microwave background to the sub-eV neutrino masses. The baryon asymmetry via the leptogenesis route is also discussed briefly.

Braneworlds, understood here as double domain wall spacetimes, can be described in terms of a linear harmonic function, with kinks at the locations of the boundary branes. In a dynamical setting, there is therefore the risk that the boundary brane of negative tension, at whose location the value of the harmonic function is always lowest, can encounter a zero of this harmonic function, corresponding to the formation of a singularity. We show that for certain types of brane-bound matter this singularity can be avoided, and the negative-tension brane can shield the bulk spacetime from the singularity by bouncing back smoothly before reaching the singularity. In our analysis we compare the 5- and 4-dimensional descriptions of this phenomenon in order to determine the validity of the moduli space approximation.

A new LISA simulator (LISACode) is presented. Its ambition is to achieve a new degree of sophistication allowing to map, as closely as possible, the impact of the different subsystems on the measurements. LISACode is not a detailed simulator at the engineering level but rather a tool whose purpose is to bridge the gap between the basic principles of LISA and a future, sophisticated end-to-end simulator. This is achieved by introducing, in a realistic manner, most of the ingredients that will influence LISA’s sensitivity as well as the application of TDI combinations. Many user-defined parameters allow the code to study different configurations of LISA thus helping to finalize the definition of the detector. Another important use of LISACode is in generating time-series for data analysis developments.

The one-loop contribution of the two $CP$-violating components of the $WW\gamma$ vertex, ${\tilde{\kappa }}_{\gamma }{W}_{\mu }^{+}{W}_{\nu }^{-}{\tilde{F}}^{\mu \nu }$ and $({\tilde{\lambda }}_{\gamma }/m_W^2)W_{\mu \nu }^{+}{W}_{\rho }^{-\nu }{\tilde{F}}^{\rho \mu }$, on the electric dipole moment (EDM) of fermions is calculated using dimensional regularization and its impact at low energies reexamined in the light of the decoupling theorem. The Ward identities satisfied by these couplings are derived by adopting a $S{U}_L(2)\times U_Y(1)$-invariant approach and their implications in radiative corrections discussed. Previous results on ${\tilde{\kappa }}_{\gamma }$, whose bound is updated to $|{\tilde{\kappa }}_{\gamma }|<5.2\times {10}^{-5}$, are reproduced, but disagreement with those existing for ${\tilde{\lambda }}_{\gamma }$ is found. In particular, the upper bound $|{\tilde{\lambda }}_{\gamma }|<1.9\times {10}^{-2}$ is found from the limit on the neutron EDM, which is more than 2 orders of magnitude less stringent than that of previous results. It is argued that this difference between the ${\tilde{\kappa }}_{\gamma }$ and ${\tilde{\lambda }}_{\gamma }$ bounds is the one that might be expected in accordance with the decoupling theorem. This argument is reinforced by analyzing carefully the low-energy behavior of the loop functions. The upper bounds on the $W$ EDM, $|d_W|<6.2\times {10}^{-21}\mathrm{e}·\mathrm{cm}$, and the magnetic quadrupole moment, $|{\tilde{Q}}_W|<3\times {10}^{-36}\mathrm{e}·{\mathrm{cm}}^2$, are derived. The EDM of the second and third families of quarks and charged leptons are estimated. In particular, EDM as large as ${10}^{-20}\mathrm{e}·\mathrm{cm}$ and ${10}^{-21}\mathrm{e}·\mathrm{cm}$ are found for the $t$ and $b$ quarks, respectively.

In order to model pions of two-flavor QCD we consider a lattice field theory involving two flavors of staggered quarks interacting strongly with $U(1)$ gauge fields. For massless quarks, this theory has an $S{U}_L(2)\times S{U}_R(2)\times U_A(1)$ symmetry. By adding a four-fermion term we can break the $U_A(1)$ symmetry and thus incorporate the physics of the QCD anomaly. We can also tune the pion decay constant $F$, to be small compared to the lattice cutoff by starting with an extra fictitious dimension, thus allowing us to model low energy pion physics in a setting similar to lattice QCD from first principles. However, unlike lattice QCD, a major advantage of our model is that we can easily design efficient algorithms to compute a variety of quantities in the chiral limit. Here we show that the model reproduces the predictions of chiral perturbation theory in the $ϵ$-regime.

We calculate the collisional energy loss of a muon of high energy $E$ in a hot QED plasma beyond logarithmic accuracy, i.e., we determine the constant terms of order $\mathcal{O}(1)$ in $-dE/dx\propto \ln E+\mathcal{O}(1)$. Considering first the $t$-channel contribution to $-dE/dx$, we show that the terms $\sim \mathcal{O}(1)$ are sensitive to the full kinematic region for the momentum exchange $q$ in elastic scattering, including large values $q\sim \mathcal{O}(E)$. We thus redress a previous calculation by Braaten and Thoma, which assumed $q\ll E$ and could not find the correct constant (in the large $E$ limit). The relevance of “very hard” momentum transfers then requires, for consistency, that $s$ and $u$-channel contributions from Compton scattering must be included, bringing a second modification to the Braaten-Thoma result. Most importantly, Compton scattering yields an additional large logarithm in $-dE/dx$. Our results might have implications in the QCD case of parton collisional energy loss in a quark gluon plasma.

We show that there are regions of parameter space in multiscalar doublet models where, in the first few hundred inverse femtobarns of data, the new charged and neutral scalars are not directly observable at the LHC and yet the Higgs decay rate to $b\overline{b}$ is changed significantly from its standard model value. For a light Higgs with a mass less than 140 GeV, this can cause a large change in the number of two photon and ${\tau }^{+}{\tau }^{-}$ Higgs decay events expected at the LHC compared to the minimal standard model. In the models we consider, the principle of minimal flavor violation is used to suppress flavor changing neutral currents. This paper emphasizes the importance of measuring the properties of the Higgs boson at the LHC; for a range of parameters the model considered has new physics at the TeV scale that is invisible, in the first few hundred inverse femtobarns of integrated luminosity at the LHC, except indirectly through the measurement of Higgs boson properties.

Leptogenesis is studied in a seesaw model with $\mu -\tau$ symmetry for $S{U}_L(2)$-singlet right-handed neutrinos. It is shown that lepton asymmetry is not zero and is given by the square of the solar neutrino mass difference and can be of the right order of magnitude. Further it involves the same Majorana phase which appears in the neutrinoless double $\beta$-decay. In this framework one of the right-handed seesaw partners of light neutrinos can be made massless. This can be identified with a sterile neutrino, once it acquires a tiny mass ($\approx 1\mathrm{eV}$) when $\mu -\tau$ symmetry is broken in the right-handed neutrino sector. The above mentioned sterile neutrino together with another one can be identified to explain the MiniBooNE and LSND results. The light $5\times 5$ neutrino mass matrix is completely fixed if $CP$ is conserved and so is the effective mass for neutrinoless double $\beta$-decay.

We investigate a novel boundary condition for the $bc$ system with central charge $c=-2$. Its boundary state is constructed and tested in detail. It appears to give rise to the first example of a local logarithmic boundary sector within a bulk theory whose Virasoro zero modes are diagonalizable.

In the first part of this paper, we present a set of simple arguments to show that the two-dimensional gauge anomaly and the ($2+1$)-dimensional Lorentz symmetry determine the leading Gaussian term in the vacuum wave function of ($2+1$)-dimensional Yang-Mills theory. This is to highlight the robustness of the wave function and its relative insensitivity to the choice of regularizations. We then comment on the correspondence with the explicit calculations done in earlier papers. We also make some comments on the nature of the gauge-invariant configuration space for Euclidean three-dimensional gauge fields (relevant to ($3+1$)-dimensional Yang-Mills theory).

Excited state soliton stars are studied numerically for the first time. The stability of spherically symmetric $S$-branch excited state oscillatons under radial perturbations is investigated using a 1D code. We find that these stars are inherently unstable either migrating to the ground state or collapsing to black holes. Higher excited state configurations are observed to cascade through intermediate excited states during their migration to the ground state. This is similar to excited state boson stars [J. Balakrishna, E. Seidel, and W.-M. Suen, Phys. Rev. D 58, 104004 (1998).]. Ground state oscillatons are then studied in full 3D numerical relativity. Finding the appropriate gauge condition for the dynamic oscillatons is much more challenging than in the case of boson stars. Different slicing conditions are explored, and a customized gauge condition that approximates polar slicing in spherical symmetry is implemented. Comparisons with 1D results and convergence tests are performed. The behavior of these stars under small axisymmetric perturbations is studied and gravitational waveforms are extracted. We find that the gravitational waves damp out on a short time scale, enabling us to obtain the complete waveform. This work is a starting point for the evolution of real scalar field systems with arbitrary symmetries.

We present single and binary black-hole simulations that follow the “moving-puncture” paradigm of simulating black-hole spacetimes without excision, and use “moving boxes” mesh refinement. Focusing on binary black-hole configurations where the simulations cover roughly two orbits, we address five major issues determining the quality of our results: numerical discretization error, finite extraction radius of the radiation signal, physical appropriateness of initial data, gauge choice, and computational performance. We also compare results we have obtained with the BAM code described here with the independent LEAN code.

Using big bang nucleosynthesis and present, high-precision measurements of light element abundances, we constrain the self-gravity of radiation pressure in the early universe. The self-gravity of pressure is strictly non-Newtonian, and thus the constraints we set provide a direct test of this prediction of general relativity and of the standard, Friedmann-Robertson-Walker cosmology.