We use the compatibility of D-brane action with linear T-duality, S-duality, and with S-matrix elements as guiding principles to find all world volume couplings of one massless closed string and two open strings at order ${\alpha }^{\prime 2}$ in type-II superstring theories. In particular, we find that the squares of second fundamental form appear only in world volume curvatures and confirm the observation that the dilaton appears in the string frame action via the transformation ${\widehat{R}}_{\mu \nu }\to {\widehat{R}}_{\mu \nu }+{\nabla }_{\mu }{\nabla }_{\nu }\mathrm{\Phi }$.

We establish a new covariant phenomenological model, which describes an influence of pseudoscalar (axion) field on spins of test massive particles. The model includes general relativistic equations of particle motion and spin evolution in background pseudoscalar (axion), electromagnetic and gravitational fields. It describes both the direct spin-axion coupling of the gradient type and indirect spin-axion interaction mediated by electromagnetic fields. Special attention is paid to the direct spin-axion coupling caused by the gradient of the pseudoscalar (axion) field. We show that it describes a spin precession, when the pseudoscalar (axion) field is inhomogeneous and/or nonstationary. Applications of the model, which correspond to the three types of four-vectors attributed to the gradient of the pseudoscalar (axion) field (timelike, spacelike, and null), are considered in detail. These are the spin precessions induced by relic cosmological axions, axions distributed around spherically symmetric static objects, and axions in a gravitational wave field, respectively. We discuss features of the obtained exact solutions and some general properties of the axionically induced spin rotation.

$f(R)$ gravity is one of the simplest theories of modified gravity to explain the accelerated cosmic expansion. Although it is usually assumed that the quasi-Newtonian approach (a combination of the quasistatic approximation and sub-Hubble limit) for cosmic perturbations is good enough to describe the evolution of large scale structure in $f(R)$ models, some studies have suggested that this method is not valid for all $f(R)$ models. Here, we show that in the matter-dominated era, the pressure and shear equations alone, which can be recast into four first-order equations to solve for cosmological perturbations exactly, are sufficient to solve for the Newtonian potential, $\mathrm{\Psi }$, and the curvature potential, $\mathrm{\Phi }$. Based on these two equations, we are able to clarify how the exact linear perturbations fit into different limits. We find that the Compton length controls the quasistatic behaviors in $f(R)$ gravity. In addition, regardless the validity of quasistatic approximation, a strong version of the sub-Hubble limit alone is sufficient to reduce the exact linear perturbations in any viable $f(R)$ gravity to second order. Our findings disagree with some previous studies where we find little difference between our exact and quasi-Newtonian solutions even up to $k=10c^{-1}{\mathcal{H}}_0$.

The use of higher-order Laguerre-Gauss modes has been proposed to decrease the influence of thermal noise in future generation gravitational-wave interferometric detectors. The main obstacle for their implementation is the degeneracy of modes with same order, which highly increases the requirements on the mirror defects, beyond the state-of-the-art polishing and coating techniques. In order to increase the mirror surface quality, it is also possible to act in situ, using a thermal source, sent on the mirrors after a proper shaping. In this paper we present the results obtained on a tabletop Fabry-Pérot Michelson interferometer illuminated with a ${\mathrm{LG}}_{3,3}$ mode. We show how an incoherent light source can reduce the astigmatism of one of the mirrors, increasing the quality of the beam in one of the Fabry-Pérot cavities and then the contrast of the interferometer. The system has the potential to reduce more complex defects and also to be used in future gravitational-wave detectors using conventional Gaussian beams.

The transition in quantum chromodynamics from hadronic matter to the quark-gluon plasma at high temperatures and/or net-baryon densities is associated with the restoration of chiral symmetry and can be investigated in the laboratory via heavy-ion collisions. We study this chiral transition within the functional renormalization group approach applied to the two-flavor version of the extended linear sigma model (eLSM). The eLSM is an effective model for the strong interaction and features besides scalar and pseudoscalar degrees of freedom also vector and axial-vector mesons. We discuss the impact of the quark masses and the axial anomaly on the order of the chiral transition. We also confirm the degeneracy of the masses of chiral partners above the transition temperature. We find that the mass of the $a_1$ meson ($\rho$ meson) decreases (increases) towards the chiral transition.

Recent measurements of PeV energy neutrinos at IceCube and a 3.5 keV x-ray line in the spectra of several galaxies are both tantalizing signatures of new physics. This paper shows that one or both of these observations can be explained within an extended supersymmetric neutrino sector. Obtaining light active neutrino masses as well as phenomenologically interesting (keV–GeV) sterile neutrino masses without any unnaturally small parameters hints at a new symmetry in the neutrino sector that is broken at the PeV scale, presumably tied to supersymmetry breaking. The same symmetry and structure can sufficiently stabilize an additional PeV particle, produce its abundance through the freeze-in mechanism, and lead to decays that can give the energetic neutrinos observed by IceCube. The lightest sterile neutrino, if at 7 keV, is a nonresonantly produced fraction of dark matter, and can account for the 3.5 keV x-ray line. The two signals could therefore be the first probes of an extended supersymmetric neutrino sector.

The rare kaon decays $K\to \pi {\ell }^{+}{\ell }^{-}$ and $K\to \pi \nu \overline{\nu }$ are flavor changing neutral current (FCNC) processes and hence promising channels with which to probe the limits of the standard model and to look for signs of new physics. In this paper we demonstrate the feasibility of lattice calculations of $K\to \pi {\ell }^{+}{\ell }^{-}$ decay amplitudes for which long-distance contributions are very significant. We show that the dominant finite-volume corrections (those decreasing as powers of the volume) are negligibly small and that, in the four-flavor theory, no new ultraviolet divergences appear as the electromagnetic current $J$ and the effective weak Hamiltonian $H_W$ approach each other. In addition, we demonstrate that one can remove the unphysical terms which grow exponentially with the range of the integration over the time separation between $J$ and $H_W$. We will now proceed to exploratory numerical studies with the aim of motivating further experimental measurements of these decays. Our work extends the earlier study by Isidori et al. [1] which focused largely on the renormalization of ultraviolet divergences. In a companion paper [2] we discuss the evaluation of the long-distance contributions to $K\to \pi \nu \overline{\nu }$ decays; these contributions are expected to be at the level of a few percent for $K^{+}$ decays.

We compare two different propagator and vertex factor formulations of spin-$3/2$ and $-5/2$ nucleon resonances by using isobar models for kaon photoproduction on the proton $\gamma +p\to K^{+}+\mathrm{\Lambda }$. All nucleon resonances listed in the Particle Data Group listing with spin up to $5/2$ and with at least a two-star rating are included in the model. The unknown coupling constants are extracted from fitting to around 7400 data points. It is found that the gauge-invariant formulation of the spin-$3/2$ and $-5/2$ interactions leads to a better agreement with experimental data. An extensive comparison of model calculation with experimental data and comparison with the previous analyses are presented. A short discussion on the cross section near the production threshold is also provided.

Dynamic $\mathrm{AdS}/\mathrm{QCD}$ is a modification of $\mathrm{AdS}/\mathrm{QCD}$ that includes the running of the anomalous dimension of the $\overline{q}q$ quark bilinear and in which the generation of the constituent quark mass plays the role of an IR wall. The model allows one to move away smoothly from the controlled spectrum of the $\mathcal{N}=2$ super Yang-Mills theory of the D3/probe-D7 system to more QCD-like theories with chiral symmetry breaking. We investigate soft wall behavior in the model that gives Regge trajectories with $M_{n,s}^2\sim n,s$. To achieve these behaviors requires the quark’s constituent mass to fall peculiarly sharply in the IR so that meson physics is sensitive to renormalization group (RG) scales well below the quark’s on-shell mass. Including soft wall behavior in models of walking gauge dynamics breaks the near conformal symmetry which is present above the quark on-shell mass which can generate a large mass for the technidilaton like state. We conclude that the meson spectrum is rather sensitive to the IR decoupling.

Real scalar fields are known to fragment into spatially localized and long-lived solitons called oscillons or $I$-balls. We prove the adiabatic invariance of the $\text{oscillons}/I$-balls for a potential that allows periodic motion even in the presence of non-negligible spatial gradient energy. We show that such a potential is uniquely determined to be the quadratic one with a logarithmic correction, for which the $\text{oscillons}/I$-balls are absolutely stable. For slightly different forms of the scalar potential dominated by the quadratic one, the $\text{oscillons}/I$-balls are only quasistable, because the adiabatic charge is only approximately conserved. We check the conservation of the adiabatic charge of the $I$-balls in numerical simulation by slowly varying the coefficient of logarithmic corrections. This unambiguously shows that the longevity of $\text{oscillons}/I$-balls is due to the adiabatic invariance.

We study the third order solutions of the cosmological density perturbations in Horndeski’s most general scalar-tensor theory under the condition that the Vainshtein mechanism is at work. In this work, we thoroughly investigate the independence property of the functions describing the nonlinear mode couplings, which is also useful for models within general relativity. Then, we find that the solutions of the density contrast and the velocity divergence up to third order are characterized by six parameters. Furthermore, the one-loop order power spectra obtained with third order solutions are described by four parameters. We exemplify the behavior of the one-loop order power spectra assuming the kinetic gravity braiding model, which demonstrates that the effect of modified gravity appears more significantly in the power spectrum of the velocity divergence than the density contrast.

Massive bigravity models are interesting alternatives to standard cosmology. In most cases, however, these models have been studied for a simplified scenario in which both metrics take homogeneous and isotropic forms [Friedmann-Lemaître-Robertson-Walker (FLRW)] with the same spatial curvatures. The interest to consider more general geometries arises, in particular, in view of the difficulty so far encountered in building stable cosmological solutions with homogeneous and isotropic metrics. Here we consider a number of cases in which the two metrics take more general forms, namely FLRW with different spatial curvatures—Lemaître, Lemaître-Tolman-Bondi (LTB), and Bianchi I—as well as cases where only one metric is linearly perturbed. We discuss possible consistent combinations and find that only some special cases of FLRW–Lemaître, LTB–LTB, and FLRW–Bianchi I combinations give consistent, nontrivial solutions.

The observed leptonic mixing pattern could be explained by the presence of a discrete flavor symmetry broken into residual subgroups at low energies. In this scenario, a residual generalized charge parity ($CP$) symmetry allows the parameters of the Pontecorvo-Maki-Nakagawa-Sakata matrix, including Majorana phases, to be predicted in terms of a small set of input parameters. In this article, we study the mixing parameter correlations arising from the symmetry group ${\mathrm{A}}_5$ including generalized $CP$ subsequently broken into all of its possible residual symmetries. Focusing on those patterns which satisfy present experimental bounds, we then provide a detailed analysis of the measurable signatures accessible to the planned reactor, superbeam and neutrinoless double-beta decay experiments. We also discuss the role which could be played by high-precision measurements from longer term projects such as the Neutrino Factory. This work provides a concrete example of how the synergies of the upcoming experimental program allow flavor symmetric models to be thoroughly investigated. Indeed, thanks to the rich tapestry of observable correlations, we find that each step of the experimental program can make important contributions to the assessment of such flavor-symmetric patterns, and ultimately all patterns that we have identified can be excluded, or strong evidence found for their continued relevance.

The supersymmetric completion of $R+R^2$ gravity is known to be equivalent to standard supergravity coupled to two chiral supermultiples with a Kähler potential of the no-scale type. The generalization of this program to $f(R)$ gravity can be carried out in an analogous framework in terms of four chiral multiplets with appropriately chosen superpotential and Kähler potential. Although the construction strategy has been known for some time, we carry out this program further by setting these theories in a closed form. The general framework considered can accommodate supergravity actions local in the scalar curvature, dual to ordinary $N=1$ supergravities. Although these are in general plagued by ghosts, the framework studied in this work offers a possibility that these can decouple as can be seen in specific examples.

We consider a model for a Planck-scale ultraviolet cutoff which is based on Shannon sampling. Shannon sampling originated in information theory, where it expresses the equivalence of continuous and discrete representations of information. When applied to quantum field theory, Shannon sampling expresses a hard ultraviolet cutoff in the form of a bandlimitation. This introduces nonlocality at the cutoff scale in a way that is more subtle than a simple discretization of space: quantum fields can then be represented as either living on continuous space or, entirely equivalently, as living on any one lattice whose average spacing is sufficiently small. We explicitly calculate vacuum entanglement entropies in $1+1$ dimensions and we find a transition between logarithmic and linear scaling of the entropy, which is the expected $1+1$ dimensional analog of the transition from an area to a volume law. We also use entanglement entropy and mutual information as measures to probe in detail the localizability of the field degrees of freedom. We find that, even though neither translation nor rotation invariance are broken, each field degree of freedom occupies an incompressible volume of space, indicating a finite information density.

Almost a century ago, Einstein used a weak field approximation around Minkowski spacetime to calculate the energy carried away by gravitational waves emitted by a time changing mass-quadrupole. However, by now there is strong observational evidence for a positive cosmological constant, $\mathrm{\Lambda }$. To incorporate this fact, Einstein’s celebrated derivation is generalized by replacing Minkowski spacetime with de Sitter spacetime. The investigation is motivated by the fact that, because of the significant differences between the asymptotic structures of Minkowski and de Sitter spacetimes, many of the standard techniques, including the usual $1/r$ expansions, cannot be used for $\mathrm{\Lambda }>0$. Furthermore, since, e.g., the energy carried by gravitational waves is always positive in Minkowski spacetime but can be arbitrarily negative in de Sitter spacetime irrespective of how small $\mathrm{\Lambda }$ is, the limit $\mathrm{\Lambda }\to 0$ can fail to be continuous. Therefore, a priori it is not clear that a small $\mathrm{\Lambda }$ would introduce only negligible corrections to Einstein’s formula. We show that, while even a tiny cosmological constant does introduce qualitatively new features, in the end, corrections to Einstein’s formula are negligible for astrophysical sources currently under consideration by gravitational wave observatories.

Using 137,562 quasars in the redshift range $2.1\le z\le 3.5$ from the data release 11 (DR11) of the baryon oscillation spectroscopic survey (BOSS) of Sloan Digital Sky Survey (SDSS)-III, the BOSS-SDSS collaboration estimated the expansion rate $H(z=2.34)=222\pm 7\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ of the Universe, and reported that this value is in tension with the predictions of flat $\mathrm{\Lambda }\mathrm{CDM}$ model at around a $2.5\sigma$ level. In this paper, we briefly describe some attempts made in the literature to relieve the tension, and show that the tension can naturally be alleviated in a nonflat $\mathrm{\Lambda }\mathrm{CDM}$ model with positive curvature. We also perform the observational consistency check by considering the constraints on the nonflat $\mathrm{\Lambda }\mathrm{CDM}$ model from Planck, WP and BAO data. We find that the nonflat $\mathrm{\Lambda }\mathrm{CDM}$ model constrained with $\text{Planck}+\mathrm{WP}$ data fits better to the line of sight measurement $H(z=2.34)=222\pm 7\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$, but only at the expense of still having a poor fit to the BAO transverse measurements.

In this paper, we consider an inflationary model that effectively behaves as a modified Chaplygin gas in the context of quintessence cosmology. We reconstruct the inflaton potential from the bottom up and using the recent observational data we fix the free parameters of the model. We show that the modified Chaplygin gas-inspired model is suitable for both the early and the late time acceleration but has shortcomings between the two periods.