We compute the one loop graviton contribution to the self-energy of a very light fermion on a locally de Sitter background. This result can be used to study the effect that a small mass has on the propagation of fermions through the sea of infrared gravitons generated by inflation. We employ dimensional regularization and obtain a fully renormalized result by absorbing all divergences with Bogliubov-Parasuik-Hepp-Zimmermann counterterms. An interesting technical aspect of this computation is the need for two noninvariant counterterms owing to the breaking of de Sitter invariance by our gauge condition.

Extreme mass ratio inspirals (EMRIs) [capture and inspiral of a compact stellar mass object into a massive black hole] are among the most interesting objects for gravitational wave astronomy. It is a very challenging task to detect those sources with the accurate estimation parameters of binaries primarily due to a large number of secondary maxima on the likelihood surface. Search algorithms based on matched filtering require computation of the gravitational waveform hundreds of thousands of times, which is currently not feasible with the most accurate (faithful) models of EMRIs. Here we propose to use a phenomenological template family which covers a large range of EMRI parameter space. We use these phenomenological templates to detect the signal in the simulated data and then, assuming a particular EMRI model, estimate the physical parameters of the binary. We have separated the detection problem, which is done in a model-independent way, from the parameter estimation. For the latter one, we need to adopt the model for inspiral in order to map phenomenological parameters onto the physical parameters characterizing EMRIs.

According to Belinskiǐ, Khalatnikov and Lifshitz (BKL), a generic spacelike singularity is characterized by asymptotic locality: Asymptotically, toward the singularity, each spatial point evolves independently from its neighbors, in an oscillatory manner that is represented by a sequence of Bianchi type I and II vacuum models. Recent investigations support this conjecture but with a modification: Apart from local BKL behavior there also exists formation of spatial structures (“spikes”) at, and in the neighborhood of, certain spatial surfaces that break asymptotic locality; the complete description of a generic spacelike singularity involves spike oscillations, which are described by sequences of Bianchi type I and certain inhomogeneous vacuum models. In this paper we describe how BKL and spike oscillations arise from concatenations of exact solutions in a Hubble-normalized state space setting, suggesting the existence of hidden symmetries and showing that the results of BKL are part of a greater picture.

The dynamical evolution of boson stars in scalar-tensor theories of gravity is considered in the physical (Jordan) frame. We focus on the study of spontaneous and induced scalarization, for which we take as initial data configurations on the well-known $S$ branch of a single boson star in general relativity. We show that during the scalarization process a strong emission of scalar radiation occurs. The new stable configurations ($S$ branch) of a single boson star within a particular scalar-tensor theory are also presented.

About $3\sigma$ deviation from the standard model prediction of muon anomalous magnetic moment (muon $g-2$) has been reported. We consider new physics beyond the standard model which has new Yukawa interactions with muons. We compute new contributions to muon $g-2$ and corrections to electroweak observables, and show the consistent region of parameter space. We find that in a simple model where the chirality flip of a muon occurs only in the external muon line in one-loop muon $g-2$ diagrams, it is necessary to introduce the relatively large new Yukawa coupling and the electroweak scale new particles. On the other hand, in a model where the chirality flip can occur in the internal fermion line of one loop muon $g-2$ diagrams, we can obtain favorable $g-2$ contributions without large Yukawa coupling, and they are consistent with the precision electroweak observables. Finally, we discuss effects of new particles for muon $g-2$ on the Higgs boson decay $h\to \gamma \gamma$ and direct productions of these particles at the LHC experiment.

We investigate pion photoproduction off the proton in a manifestly gauge-invariant chiral unitary extension of chiral perturbation theory. In a first step, we consider meson-baryon scattering taking into account all next-to-leading order contact interactions. The resulting low-energy constants are determined by a fit to $s$-wave pion-nucleon scattering and the low-energy data for the reaction ${\pi }^{-}p\to \eta n$. To assess the theoretical uncertainty, we perform two different fit strategies. Having determined the low-energy constants, we then analyze the data on the $s$-wave multipole amplitudes $E_{0+}$ of pion and eta photoproduction. These are parameter-free predictions, as the two new low-energy constants are determined by the neutron and proton magnetic moments.

The critical end point (CEP) and the critical behavior in its vicinity have been explored in the two-flavor effective chiral models with and without the presence of an effective Polyakov loop potential. The tricritical point (TCP) in the massless chiral limit has been located on the phase diagram in the $\mu$ and $T$ plane for the Polyakov loop-extended quark-meson model (PQM) and the pure quark-meson model, which become effective quantum chromodynamics (QCD)-like models due to the proper accounting of fermionic vacuum loop contributions in the effective potential. The proximity of the TCP to the QCD critical end point (CEP) has been quantified in the phase diagram. The critical region around the CEP has been obtained in both the presence and absence of fermionic vacuum-loop contributions in the effective potentials of the PQM and quark-meson models. The contours of appropriately normalized constant quark number susceptibility and scalar susceptibility have been plotted around the CEP in different model scenarios. These contours determine the shape of the critical region and facilitate comparisons between different models such that the influence of the fermionic vacuum term and the Polyakov loop potential on the critical behavior around the CEP can be ascertained in qualitative as well as quantitative terms. Critical exponents resulting from the divergence of quark number susceptibility at the CEP have been calculated and compared with those in different model scenarios. The possible influence of the TCP on the critical behavior around the CEP has also been discussed. The temperature variation of $\sigma$ and $\pi$ meson masses at $\mu =0$, $\mu ={\mu }_{\mathrm{CEP}}$, and $\mu >{\mu }_{\mathrm{CEP}}$ has been shown and compared with that seen in different model scenarios and the emerging mass degeneration trend in the $\sigma$ and $\pi$ meson mass variations has been inferred as the chiral-symmetry restoration takes place at higher temperatures.

In the presence of cosmic chiral asymmetry, chiral-vorticity and chiral-magnetic effects can play an important role in the generation and evolution of magnetic fields in the early universe. We include these chiral effects in the magnetic field equations and find solutions under simplifying assumptions. Our numerical and analytical results show the presence of an attractor solution in which chiral effects produce a strong, narrow, Gaussian peak in the magnetic spectrum and the magnetic field becomes maximally helical. The peak in the spectrum shifts to longer length scales and becomes sharper with evolution. We also find that the dynamics may become nonlinear for certain parameters, pointing to the necessity of a more complete analysis.

We study the orientifold daughter of $\mathcal{N}=4$ super-Yang-Mills as a candidate nonsupersymmetric large-$N$ conformal field theory. In a theory with vanishing single-trace beta functions that contains scalars in the adjoint representation, conformal invariance might still be broken by renormalization of double-trace terms to leading order at large $N$. In this note we perform a diagrammatic analysis and argue that the orientifold daughter does not suffer from double-trace running. This implies an exact large-$N$ equivalence between this theory and a subsector of $\mathcal{N}=4$ super-Yang-Mills.

We study supernova neutrino flux variations in the IceCube detector, using 3D models based on a simplified neutrino transport scheme. The hemispherically integrated neutrino emission shows significantly smaller variations compared with our previous study of 2D models, largely because of the reduced activity of the standing accretion shock instability in this set of 3D models which we interpret as a pessimistic extreme. For the studied cases, intrinsic flux variations up to about 100 Hz frequencies could still be detected in a supernova closer than about 2 kpc.

We show that a possible violation of the Robertson-Schrödinger uncertainty principle may signal the existence of a deformation of the Heisenberg-Weyl algebra. More precisely, we prove that any Gaussian in phase space (even if it violates the Robertson-Schrödinger uncertainty principle) will always be a quantum state of an appropriate noncommutative extension of quantum mechanics. Conversely, all canonical noncommutative extensions of quantum mechanics display states that violate the Robertson-Schrödinger uncertainty principle.

The 3-point vertices of QCD are examined at the symmetric subtraction point at one loop in the Landau gauge in the presence of the Gribov mass, $\gamma$. They are expanded in powers of ${\gamma }^2$ up to dimension four in order to determine the order of the leading correction. As well as analyzing the pure Gribov-Zwanziger Lagrangian, its extensions to include localizing ghost masses are also examined. For comparison a pure gluon mass term is also considered.

We find novel perturbative fixed points by introducing mildly spacetime dependent couplings into otherwise marginal terms. In four-dimensional quantum field theory, these are physical analogues of the small-$ϵ$ Wilson-Fisher fixed point. Rather than considering $4-ϵ$ dimensions, we stay in four dimensions but introduce couplings whose leading spacetime dependence is of the form $\lambda x^{\kappa }{\mu }^{\kappa }$, with a small parameter $\kappa$ playing a role analogous to $ϵ$. We show, in ${\varphi }^4$ theory and in QED and QCD with massless flavors, that this leads to a critical theory under perturbative control over an exponentially wide window of spacetime positions $x$. The exact fixed point coupling ${\lambda }_{*}(x)$ in our theory is identical to the running coupling of the translationally invariant theory, with the scale replaced by $1/x$. Similar statements hold for three-dimensional ${\varphi }^6$ theories and two-dimensional sigma models with curved target spaces. We also describe strongly coupled examples using conformal perturbation theory.

The scaling properties of quantum gravity are discussed by employing a class of proper-time regulators in the functional flow equation for the conformal factor within the formalism of the background field method. Renormalization group trajectories obtained by projecting the flow on a flat topology are more stable than those obtained from a projection on a spherical topology. In the latter case the ultraviolet flow can be characterized by a Hopf bifurcation with an ultraviolet attractive limiting cycle. Although the possibility of determining the infrared flow for an extended theory space can be severely hampered due to the conformal factor instability, we present a robust numerical approach to study the flow structure around the non-Gaussian fixed point as an inverse problem. In particular, we show that the possibility of having a spontaneous breaking of the diffeomorphism invariance can be realized with nonlocal functionals of the volume operator.

We construct gravitating superconducting string solutions of the $U(1{)}_{\mathrm{local}}\times U(1{)}_{\mathrm{global}}$ model by solving the coupled system of Einstein and matter field equations numerically. We study the properties of these solutions in dependence on the symmetry breaking to Planck mass ratio. Using the macroscopic stability conditions formulated by Carter, we observe that the coupling to gravity allows for a new stable region that is not present in the flat space-time limit. We match the asymptotic metric to the Kasner metric and show that the relations between the Kasner coefficients and the energy per unit length and tension suggested previously are well fulfilled for symmetry breaking scale much smaller than the Planck mass. We also study the solutions to the geodesic equation in this space-time. While geodesics in the exterior space-time of standard cosmic strings are just straight lines, test particles experience a force in a general Kasner space-time, and as such, bound orbits are possible.

In this work we analyze how effects of finite size may modify the thermodynamics of a system of strongly interacting fermions that we model using an effective field theory with four-point interactions at finite temperature and density and look in detail at the case of a confining two-layer system. We compute the thermodynamic potential in the large-$N$ and mean-field approximations and adopt a zeta-function regularization scheme to regulate the divergences. Explicit expansions are obtained in different regimes of temperature and separation. The analytic structure of the potential is carefully analyzed, and relevant integral and series representations for the various expressions involved are obtained. Several known results are obtained as a limiting case of general results. We numerically implement the formalism and compute the thermodynamic potential, the critical temperature, and the fermion condensate showing that effects of finite size tend to shift the critical points and the order of the transitions. The present discussion may be of some relevance for the study of the Casimir effect between strongly coupled fermionic materials with interlayer interactions.

Spherically symmetric static topological black hole solutions associated with some extended higher order gravitational models in the presence of a Maxwell field are derived by means of simple Lagrangian method, based on spherically symmetric reduction. Some new topological black hole solutions are presented and the validity of the first law is investigated, and in these cases an expression for the energy is provided.

We derive spin-dominated waveforms (SDW) for binary systems composed of spinning black holes with unequal masses (less than $1:30$). Such systems could be formed by an astrophysical black hole with a smaller black hole or a neutron star companion; and typically arise for supermassive black hole encounters. SDW characterize the last stages of the inspiral, when the larger spin dominates over the orbital angular momentum (while the spin of the smaller companion can be neglected). They emerge as a double expansion in the post-Newtonian parameter $\epsilon$ and the ratio $\xi$ of the orbital angular momentum and dominant spin. The SDW amplitudes are presented to $({\epsilon }^{3/2},\xi )$ orders, while the phase of the gravitational waves to $({\epsilon }^2,\xi )$ orders (omitting the highest order mixed terms). To this accuracy the amplitude includes the (leading order) spin-orbit contributions, while the phase the (leading order) spin-orbit, self-spin and mass quadrupole-monopole contributions. While the SDW hold for any mass ratio smaller than $1:30$, lower bounds for the mass ratios are derived from the best sensitivity frequency range expected for Advanced LIGO (giving $1:140$), the Einstein Telescope ($7\times {10}^{-4}$), the LAGRANGE ($7\times {10}^{-7}$) and LISA missions ($7\times {10}^{-9}$), respectively.