Detecting a stochastic gravitational wave background requires that we first understand and model any astrophysical foregrounds. In the millihertz frequency band, the predominate foreground signal will be from unresolved white dwarf binaries in the galaxy. We build on our previous work to show that a stochastic gravitational wave background can be detected in the presence of both instrument noise and a galactic confusion foreground. The key to our approach is accurately modeling the spectra for each of the various signal components. We simulate data for a gigameter Laser Interferometer Space Antenna operating in the millihertz frequency band with both six and four links. We obtain posterior distribution functions for the instrument noise parameters, the galaxy level and modulation parameters, and the stochastic background energy density. We find that we are able to detect a scale-invariant stochastic background with energy density as low as ${\mathrm{\Omega }}_{\mathrm{gw}}=2\times 10^{-13}$ for a six-link interferometer and ${\mathrm{\Omega }}_{\mathrm{gw}}=5\times 10^{-13}$ for a four-link interferometer with one year of data.

We compute the full cosmic microwave background temperature bispectrum generated by nonlinearities after single-field inflation. By integrating the photon temperature at second order along a perturbed geodesic in Newtonian gauge, we derive an expression for the observed temperature fluctuations that, for the first time, clarifies the separation of the gravitational lensing and time-delay effects from the purely second-order contributions. We then use the second-order Boltzmann code CosmoLib2nd to calculate these contributions and their bispectrum. Including the perturbations in the photon path, the numerically computed bispectrum exactly matches the expected squeezed limit. Moreover, the analytic squeezed-limit formula reproduces well the signal-to-noise ratio and shape of the full bispectrum, potentially facilitating the subtraction of the bias induced by second-order effects. For a cosmic-variance limited experiment with $l_{\max }=2000$, the bias on a local signal is $f_{\mathrm{NL}}^{\text{loc}}=0.73$ negligible for equilateral and orthogonal signals. The signal-to-noise ratio is unity at $l_{\max }\sim 3000$, suggesting that second-order effects may hopefully be measured in the future.

This paper reports on the determination of ${\alpha }_S$ from lattice simulations with $2+1+1$ twisted-mass dynamical flavors via the computation of the ghost-gluon coupling renormalized in the momentum substraction Taylor scheme. A high-statistics sample of gauge configurations used to evaluate the coupling from ghost and gluon propagators allows for the appropriate update of previous results, now performing an improved analysis of data with reduced statistical errors and the systematical uncertainties under a better control.

We measure the inclusive single muon charge asymmetry and the like-sign dimuon charge asymmetry in $p\bar{p}$ collisions using the full data set of $10.4{\mathrm{fb}}^{-1}$ collected with the D0 detector at the Fermilab Tevatron. The standard model predictions of the charge asymmetries induced by $CP$ violation are small in magnitude compared to the current experimental precision, so nonzero measurements could indicate new sources of $CP$ violation. The measurements differ from the standard model predictions of $CP$ violation in these asymmetries with a significance of 3.6 standard deviations. These results are interpreted in a framework of $B$ meson mixing within the Cabibbo-Kobayashi-Maskawa formalism to measure the relative width difference $\mathrm{\Delta }{\mathrm{\Gamma }}_d/{\mathrm{\Gamma }}_d$ between the mass eigenstates of the $B^0$ meson system and the semileptonic charge asymmetries $a_{\mathrm{sl}}^d$ and $a_{\mathrm{sl}}^s$ of $B^0$ and $B_s^0$ mesons, respectively.

We investigate the influence of noninertial effects on the ground state energy of a massive scalar field in the cosmic string spacetime. We generalize the results obtained by Khusnutdinov and Bordag [, Phys. Rev. D 59, 064017 (1999)] to a noninertial reference frame and show, by contrast, that a nonvanishing contribution to the ground state energy stems from the noninertial effects. Moreover, we show that there is no influence of the curvature of the spacetime on this nonvanishing contribution to the ground state energy of a massive scalar field.

We exhibit novel effects (absent in GR) of sources in massive gravity. First, we show that removing its ghost mode forces a field-current identity: The metric’s trace is locally proportional to that of its stress tensor; a point source implies a metric singularity enhanced by the square of the graviton’s range. Second, exterior solutions acquire spatial stress hair—their metric components depend on the interior $T_{ij}$. Also, in contrast to naïve expectations, the Newtonian potential of a source is now determined by both its spatial stress and mass. Our explicit results are obtained at linear, Fierz–Pauli, level but qualitatively persist nonlinearly.

The Doppler effect is commonly used to infer the velocity difference between stars based on the relative shifts in the rest-frame wavelengths of their spectral features. In dynamically cold systems with a low velocity dispersion, such as wide binaries, loose star clusters, cold stellar streams or cosmological minihalos, the scatter in the gravitational redshift from the surface of the constituent stars needs to be taken into account as well. Gravitational redshifts could be important for wide binaries composed of main sequence stars with separations $\gtrsim 10^{-2}\mathrm{pc}$ or in minihalos with velocity dispersions $\lesssim 1\mathrm{km}{\mathrm{s}}^{-1}$. Variable redshift could also lead to a spurious “detection” of low-mass planets around a star with periodic photospheric radius variations.

We study the phase diagram of a holographic model realizing a $U(2)$ global symmetry on the boundary and show that at low temperature a phase with both scalar $s$ and vector $p$ condensates exists. This is the $s+p$-wave phase where the global $U(2)$ symmetry and also the spatial rotational symmetry are spontaneously broken. By studying the free energy we show that this phase is preferred when it exists. We also consider unbalanced configurations where a second chemical potential is turned on. They present a rich phase diagram characterized by the competition and coexistence of the $s$ and $p$ order parameters.

Since any string theory involves a path integration on the world-sheet metric, their partition functions are volume forms on the moduli space of genus $g$ Riemann surfaces ${\mathcal{M}}_g$, or on its super analog. It is well known that modular invariance fixes strong constraints that in some cases appear only at higher genus. Here we classify all the Weyl and modular invariant partition functions given by the path integral on the world-sheet metric, together with space-time coordinates, $b\text{−}c$ and/or $\beta \text{−}\gamma$ systems, that correspond to volume forms on ${\mathcal{M}}_g$. This was a long standing question, advocated by Belavin and Knizhnik, inspired by the Serre GAGA principle and based on the properties of the Mumford forms. The key observation is that the Bergman reproducing kernel provides a Weyl and modular invariant way to remove the point dependence that appears in the above string determinants, a property that should have its superanalog based on the super Bergman reproducing kernel. This is strictly related to the properties of the propagator associated to the space-time coordinates. Such partition functions $\mathcal{Z}[\mathcal{J}]$ have well-defined asymptotic behavior and can be considered as a basis to represent a wide class of string theories. In particular, since noncritical bosonic string partition functions ${\mathcal{Z}}_D$ are volume forms on ${\mathcal{M}}_g$, we suggest that there is a mapping, based on bosonization and degeneration techniques, from the Liouville sector to first order systems that may identify ${\mathcal{Z}}_D$ as a subclass of the $\mathcal{Z}[\mathcal{J}]$. The appearance of $b\text{−}c$ and $\beta \text{−}\gamma$ systems of any conformal weight shows that such theories are related to $W$ algebras. The fact that in a large $N$ ’t Hooft-like limit two-dimensional $W_N$ minimal models conformal field theories are related to higher spin gravitational theories on ${\mathrm{AdS}}_3$, suggests that the string partition functions introduced here may lead to a formulation of higher spin theories in a string context.

The perihelion precession of planetary orbits and the bending angle of null geodesics are estimated for different gravity theories in string-inspired models. It is shown that, for dilaton coupled gravity, the leading order measure in the angle of bending of light comes purely from vacuum expectation value of the dilaton field which may be interpreted as an indicator of a dominant stringy effect over the curvature effect. We arrive at similar results for a spherically symmetric solution in quadratic gravity. We also present the perihelion shift and bending of light in the Einstein-Maxwell-Gauss-Bonnet theory with special reference to the Casimir effect and Damour-Polyakov mechanism. Numerical bounds to different coupling parameters in these models are estimated.

We construct a spherical domain wall which has baryon charge distributed on a sphere of finite radius in a Skyrme model with a sixth-order derivative term and a modified mass term. Its distribution of energy density likewise takes the form of a sphere. In order to localize the domain wall at a finite radius we need a negative coefficient in front of the Skyrme term and a positive coefficient of the sixth order derivative term to stabilize the soliton. Increasing the pion mass pronounces the shell-like structure of the configuration.

We find the general solution to the time-dependent Hartree-Fock problem for scattering solutions of the Gross–Neveu models, with both discrete (${\mathrm{GN}}_2$) and continuous (${\mathrm{NJL}}_2$) chiral symmetry. We find new multibreather solutions both for the ${\mathrm{GN}}_2$ model, generalizing the Dashen–Hasslacher–Neveu breather solution, and also new twisted breathers for the ${\mathrm{NJL}}_2$ model. These solutions satisfy the full time-dependent Hartree-Fock consistency conditions, and only in the special cases of ${\mathrm{GN}}_2$ kink scattering do these conditions reduce to the integrable Sinh–Gordon equation. We also show that all baryons and breathers are composed of constituent twisted kinks of the ${\mathrm{NJL}}_2$ model. Our solution depends crucially on a general class of transparent, time-dependent Dirac potentials found recently by algebraic methods.

We propose a method for constructing pairs of nonsupersymmetric gauge theories related by $S$-duality. Starting from a known $S$-duality of supersymmetric theories realized on the worldvolume of D3 branes in type IIB string theory, a new duality is obtained by replacing the D3 branes with antibranes. Large classes of dual pairs of nonsupersymmetric theories can be obtained in this way, with different interactions and matter content (chiral and vectorlike). The approach is illustrated on gauge theories realized on three-branes and fractional branes probing orbifold singularities. The duality sheds light on the dynamics of gauge theories and their possible infrared phases by providing concrete magnetic dual descriptions of strongly coupled theories. Some of the models share various properties with QCD, including confinement and chiral symmetry breaking. More generally, these theories feature fermions in multiple two-index representations and could realize intriguing phases such as a free magnetic phase with chiral symmetry breaking or mixed phases where an interacting fixed point coexists with a confining phase.

We investigate the properties of the horizons and ergosphere in a rotating higher dimensional (HD) deformed Kerr-like black hole. We also explicitly bring out the effect of deformation parameter $\epsilon$ and the extra dimension on the efficiency of the Penrose process of energy extraction from a black hole. It is interesting to see that the ergosphere size is sensitive to the deformation parameter $\epsilon$ as well as spacetime dimensions $D$. This gives rise to a much richer structure of the ergosphere in a HD non-Kerr black hole, thereby making the Penrose process more efficient compared with that of the four-dimensional Kerr black hole.

We study the entanglement between two modes of Dirac field in an expanding spacetime characterized by the Robertson-Walker metric. This spacetime model turns out to be asymptotically (in the remote past and far future regions) Minkowskian. Then, on the one hand we show entanglement creation between particles and antiparticles when passing from remote past to far future. On the other hand, we show that particles entanglement in the remote past degrades into the far future. These effects are traced back to particle creation. In our analysis we highlight the role of spin (polarization) of particles and compare the results with those obtainable without accounting for it.

We derive the covariant equations of motion for Maxwell field theory and electrodynamics in multiscale spacetimes with weighted Laplacian. An effective spacetime-dependent electric charge of geometric origin naturally emerges from the theory, thus giving rise to a varying fine-structure constant. The theory is compared with other varying-coupling models, such as those with a varying electric charge or varying speed of light. The theory is also confronted with cosmological observations, which can place constraints on the characteristic scales in the multifractional measure. We note that the model considered here is fundamentally different from those previously proposed in the literature, either of the varying-$e$ or varying-$c$ persuasion.

We study high energy particle collisions around higher dimensional black holes. It is shown that the center of mass energy can be arbitrarily large in the vicinity of the event horizon like the Bañados, Silk and West (BSW) process in four dimensions if the following two conditions are satisfied: (i) the horizon is extremal and (ii) the parameters of either of the two colliding particles are fine-tuned, which is called a critical particle condition. We also show that a test particle which satisfies the critical particle condition can reach the event horizon from a distant region for a simple case. Finally, we discuss the relation between the BSW process and the linear instability of test fields around extremal black holes, the latter of which has been recently found by Aretakis [Commun. Math. Phys. 307, 17 (2011); Ann. Inst. Henri Poincaré 12, 1491 (2011); J. Funct. Anal. 263, 2770 (2012); arXiv:1206.6598; Classical Quantum Gravity 30, 095010 (2013); Phys. Rev. D 87, 084052 (2013)].

We consider the thermal corrections to the Casimir energy of a massless scalar field in the space-time with topology $S^3\times R^1$ (Einstein and Friedmann universes) containing an idealized cosmic string. The vacuum energy of the field under consideration, in this background, can be separated in two terms: one term that is simply the known vacuum energy of the massless scalar field in the Einstein and Friedmann cosmological models and the other term that formally corresponds to the vacuum energy of the electromagnetic field, also in the Einstein and Friedmann universes, multiplied by the cosmic string parameter $\lambda =(1/\alpha )-1$, where $\alpha$ is a constant related to the cosmic string tension, $G\mu$. The Casimir free energy and all the other thermodynamic expressions can also be separated in the same way. Thus, we use the expressions calculated in previous works for the massless scalar and electromagnetic fields in the closed Einstein and Friedmann models to investigate the low- and high-temperature limits of the Casimir free energy, internal energy, and entropy and show the role played by the presence of a cosmic string.

We introduce a method to compute a particle detector transition probability in spacetime regions of general curved spacetimes provided that the curvature is not above a maximum threshold. In particular we use this method to compare the response of two detectors, one in a spherically symmetric gravitational field and the other one in Rindler spacetime to compare the Unruh and Hawking effects: we study the vacuum response of a detector freely falling through a stationary cavity in a Schwarzschild background as compared to the response of an equivalently accelerated detector traveling through an inertial cavity in the absence of curvature. We find that as we set the cavity at increasingly further radii from the black hole, the thermal radiation measured by the detector approaches the quantity recorded by the detector in Rindler background showing in which way and at what scales the equivalence principle is recovered in the Hawking-Unruh effect. i.e. when the Hawking effect in a Schwarzschild background becomes equivalent to the Unruh effect in Rindler spacetime.

We consider the total energy loss and spectral density of uniformly moving electrically charged particles in the spacetime of a wormhole with an infinitely short throat. We show that the total energy loss $\mathcal{E}\sim e^{2}v\gamma a^2/b^3$, where $\gamma$ is relativistic factor, $a$ is the radius of the wormhole’s throat, and $b$ is the impact factor. The spectrum of the energy for particles radially moving through the wormhole’s throat is $\mathcal{E}\sim e^{2}v\gamma /a$. The spectral density of the total energy has a maximum at frequency ${\omega }_m\sim v\gamma /b$ and at ${\omega }_m\sim v\gamma /a$ for radial motion.