In this paper, we study the physical properties and the equilibrium thermal radiation emission characteristics of matter forming thin accretion disks in stationary axially symmetric wormhole spacetimes. The thin disk models are constructed by taking different values of the wormhole’s angular velocity, and the time averaged energy flux, the disk temperature, and the emission spectra of the accretion disks are obtained. Comparing the mass accretion in a rotating wormhole geometry with the one of a Kerr black hole, we verify that the intensity of the flux emerging from the disk surface is greater for wormholes than for rotating black holes with the same geometrical mass and accretion rate. We also present the conversion efficiency of the accreting mass into radiation, and show that the rotating wormholes provide a much more efficient engine for the transformation of the accreting mass into radiation than the Kerr black holes. Therefore specific signatures appear in the electromagnetic spectrum of thin disks around rotating wormholes, thus leading to the possibility of distinguishing wormhole geometries by using astrophysical observations of the emission spectra from accretion disks.

We consider dynamics of vacuum decay and particle production in the context of short pulse laser experiments. We identify and evaluate the invariant “materialization time,” $\tau$, the time scale for the conversion of an electromagnetic field energy into particles and compare to the laser related time scales.

We study the potential of future high energy $e^{+}{e}^{-}$ colliders to probe excited neutrino signals in different channels coming from the single production process via gauge interactions. We calculate the production cross section, decay widths, and branching ratios of excited spin-$3/2$ neutrinos according to their effective currents and we compare them with those of the spin-$1/2$ ones. The signals and corresponding backgrounds are examined in detail to get accessible limits on the masses and couplings of excited spin-$3/2$ neutrinos.

A new approach to study the equation of state in finite-temperature QCD is proposed on the lattice. Unlike the conventional method in which the temporal lattice size $N_t$ is fixed, the temperature $T$ is varied by changing $N_t$ at the fixed lattice scale. The pressure of the hot QCD plasma is calculated by the integration of the trace anomaly with respect to $T$ at the fixed lattice scale. This “$T$-integral method” is tested in quenched QCD on isotropic and anisotropic lattices and is shown to give reliable results, especially at intermediate and low temperatures.

The kinematic approach to cosmological tests provides direct evidence to the present accelerating stage of the Universe that does not depend on the validity of general relativity, as well as on the matter-energy content of the Universe. In this context, we consider here a linear two-parameter expansion for the decelerating parameter, $q(z)=q_0+q_{1}z$, where $q_0$ and $q_1$ are arbitrary constants to be constrained by the union supernovae data. By assuming a flat Universe we find that the best fit to the pair of free parameters is $(q_0,q_1)=(-0.73,1.5)$ whereas the transition redshift is $z_t={0.49}_{-0.07}^{+0.14}(1\sigma )$ $\genfrac{}{}{0ex}{}{+0.54}{-0.12}(2\sigma )$. This kinematic result is in agreement with some independent analyses and more easily accommodates many dynamical flat models (like $\Lambda \mathrm{CDM}$).

Although the MiniBooNE experiment has severely restricted the possible existence of light sterile neutrinos, a few anomalies persist in oscillation data, and the possibility of extra light species contributing as a subdominant hot (or warm) component is still interesting. In many models, this species would be in thermal equilibrium in the early universe and share the same temperature as active neutrinos, but this is not necessarily the case. In this work, we fit up-to-date cosmological data with an extended $\Lambda \mathrm{CDM}$ model, including light relics with a mass typically in the range 0.1–10 eV. We provide, first, some nearly model-independent constraints on their current density and velocity dispersion, and second, some constraints on their mass, assuming that they consist either in early decoupled thermal relics, or in nonresonantly produced sterile neutrinos. Our results can be used for constraining most particle-physics-motivated models with three active neutrinos and one extra light species. For instance, we find that at the $3\sigma$ confidence level, a sterile neutrino with mass $m_s=2\mathrm{eV}$ can be accommodated with the data provided that it is thermally distributed with $T_s/T_{\nu }^{\mathrm{id}}\lesssim 0.8$ or nonresonantly produced with $\Delta N_{\mathrm{eff}}\lesssim 0.5$. The bounds become dramatically tighter when the mass increases. For $m_s\lesssim 0.9\mathrm{eV}$ and at the same confidence level, the data is still compatible with a standard thermalized neutrino.

In the first part of this work we show the decoupling (up to contact terms) of redundant degrees of freedom which appear in the covariant description of spin-two massive particles in $D=2+1$. We make use of a master action which interpolates, without solving any constraints, between a first-, second-, and third-order (in derivatives) self-dual model. An explicit dual map between those models is derived. In our approach the absence of ghosts in the third-order self-dual model, which corresponds to a quadratic truncation of topologically massive gravity, is due to the triviality (no particle content) of the Einstein-Hilbert action in $D=2+1$. In the second part of the work, also in $D=2+1$, we prove the quantum equivalence of the gauge invariant sector of a couple of self-dual models of opposite helicities ($+2$ and $-2$) and masses $m_{+}$ and $m_{-}$ to a generalized self-dual model which contains a quadratic Einstein-Hilbert action, a Chern-Simons term of first order, and a Fierz-Pauli mass term. The use of a first-order Chern-Simons term instead of a third-order one avoids conflicts with the sign of the Einstein-Hilbert action.

We use the evolution operator method to find the Schwinger pair-production rate at finite temperature in scalar and spinor QED by counting the vacuum production, the induced production, and the stimulated annihilation from the initial ensemble. It is shown that the pair-production rate for each state is factorized into the mean number at zero temperature and the initial thermal distribution for bosons and fermions.

We investigate five-dimensional braneworld setups with broken Lorentz invariance continuing the developments of [P. Koroteev and M. Libanov, J. High Energy Phys. 02 (2008) 104], where a family of static self-tuning braneworld solutions was found. We show that several known braneworld models can be embedded into this family. Then we give a qualitative analysis of spectra of field fluctuations in backgrounds with broken Lorentz invariance. We also elaborate on one particular model and study spectra of scalar and spinor fields in it. It turns out that the spectra we have found possess very peculiar and unexpected properties.

We study exact solutions to cosmological topologically massive gravity coupled to topologically massive electrodynamics at special values of the coupling constants. For the particular case of the so-called chiral point $l{\mu }_G=1$, vacuum solutions (with vanishing gauge field) are exhibited. These correspond to a one-parameter deformation of general relativity solutions, and are continuously connected to the extremal Bañados-Teitelboim-Zanelli black hole with bare constants $J=-lM$. At the chiral point this extremal Bañados-Teitelboim-Zanelli black hole turns out to be massless, and thus it can be regarded as a kind of ground state. Although the solution is not asymptotically ${\mathrm{AdS}}_3$ in the sense of Brown-Henneaux boundary conditions, it does obey the weakened asymptotic recently proposed by Grumiller and Johansson. Consequently, we discuss the holographic computation of the conserved charges in terms of the stress tensor in the boundary. For the case where the coupling constants satisfy the relation $l{\mu }_G=1+2l{\mu }_E$, electrically charged analogues to these solutions exist. These solutions are asymptotically ${\mathrm{AdS}}_3$ in the strongest sense, and correspond to a logarithmic branch of self-dual solutions previously discussed in the literature.

We argue that quintessence may reside in certain corners of the string landscape. It arises as a linear combination of internal space components of higher-rank forms, which are axionlike at low energies, and may mix with 4-forms after compactification of the Chern-Simons terms to 4D due to internal space fluxes. The mixing induces an effective mass term, with an action which preserves the axion shift symmetry, breaking it spontaneously after the background selection. With several axions, several 4-forms, and a low string scale, as in one of the setups already invoked for dynamically explaining a tiny residual vacuum energy in string theory, the 4D mass matrix generated by random fluxes may have ultralight eigenmodes over the landscape, which are quintessence. We illustrate how this works in the simplest cases, and outline how to get the lightest mass to be comparable to the Hubble scale now, $H_0\sim {10}^{-33}\mathrm{eV}$. The shift symmetry protects the smallest mass from perturbative corrections in field theory. Further, if the ultralight eigenmode does not couple directly to any sector strongly coupled at a high scale, the nonperturbative field theory corrections to its potential will also be suppressed. Finally, if the compactification length is larger than the string length by more than an order of magnitude, the gravitational corrections may remain small too, even when the field value approaches $M_{\mathrm{Pl}}$.

Spinning black hole pairs exhibit a range of complicated dynamical behaviors. An interest in eccentric and zoom-whirl orbits has ironically inspired the focus of this paper: the constant radius orbits. When black hole spins are misaligned, the constant radius orbits are not circles but, rather, they lie on the surface of a sphere and have acquired the name “spherical orbits.” The spherical orbits are significant as they energetically frame the distribution of all orbits. In addition, each unstable spherical orbit is asymptotically approached by an orbit that whirls an infinite number of times, known as a homoclinic orbit. A homoclinic trajectory is an infinite whirl limit of the zoom-whirl spectrum and has a further significance as the separatrix between inspiral and plunge for eccentric orbits. We work in the context of two spinning black holes of comparable mass as described in the third-order post-Newtonian Hamiltonian with spin-orbit coupling included. As such, the results could provide a testing ground for the accuracy of the post-Newtonian expansion. Further, the spherical orbits could provide useful initial data for numerical relativity. Finally, we comment that the spinning black hole pairs should give way to chaos around the homoclinic orbit when spin-spin coupling is incorporated.

Although the orbits of comparable-mass, spinning black holes seem to defy simple decoding, we find a means to decipher all such orbits—in the absence of radiation reaction. The conservative dynamics is complicated by extreme perihelion precession compounded by spin-induced precession. We are able to quantitatively define and describe the fully three-dimensional motion of comparable-mass binaries with one black hole spinning and expose an underlying simplicity. To do so, we untangle the dynamics by capturing the motion in the orbital plane and explicitly separate out the precession of the plane itself. Our system is defined by the conservative third-order post-Newtonian Hamiltonian plus spin-orbit coupling for one spinning black hole with a nonspinning companion. Our results are twofold: (1) We derive highly simplified equations of motion in a nonorthogonal orbital basis, and (2) we define a complete taxonomy for fully three-dimensional orbits. More than just a naming system, the taxonomy provides unambiguous and quantitative descriptions of the orbits, including a determination of the zoom-whirliness of any given orbit. Through a correspondence with the rationals, we are able to show that zoom-whirl behavior is prevalent in comparable-mass binaries in the strong-field regime, as it is for extreme-mass-ratio binaries in the strong field. A first significant conclusion that can be drawn from this analysis is that all generic orbits in the final stages of inspiral under gravitational radiation losses are characterized by precessing clovers with few leaves, and that no orbit will behave like the tightly precessing ellipse of Mercury. The gravitational waveform produced by these low-leaf clovers will reflect the natural harmonics of the orbital basis—harmonics that, importantly, depend only on radius. The significance for gravitational wave astronomy will depend on the number of windings the pair executes in the strong-field regime. The third-order post-Newtonian system studied provides an example of a general method that can be applied to any effective description of black hole pairs.

The usual inflationary scenario predicts a Gaussian random primordial density fluctuation, different Fourier modes of which do not correlate with each other. In this paper we propose a correlation between these different modes. A simple case is that these different Fourier modes correlate with each other following a Gaussian function. For such a primordial density fluctuation we calculate the cosmic microwave background angular power spectrum and find that its amplitude decreases but the decrease is different for different $l$. This feature can be used to constrain the correlation strength from the real data.

We provide a new, independent, and analytic estimate of the lowest glueball mass, and we found it at 1661 MeV within a relativistic quantum-field model based on analytic confinement. The conventional mesons and the weak decay constants are described to extend the consideration. For the spectra of two-gluon and two-quark bound states we solve the ladder Bethe-Salpeter equation. By using a minimal set of model parameters (the quark masses, the coupling constant, and the confinement scale) we obtain numerical results which are in reasonable agreement with experimental evidence in the wide range of energy scale. The model serves a reasonable framework to describe simultaneously different sectors in low-energy particle physics.

The lepton-number-violating decays of $B^{+}$, $D^{+}$, and $D_s^{+}$ mesons induced by the doubly charged Higgs boson have been studied. It is found that although the yielded results of the branch ratio are much smaller than the present limits from the data, they are consistent with the previous conclusions calculated in the framework of the relativistic quark model where the processes happened via light Majorana neutrinos.

The correlation function of two pseudoscalar charmed quark currents with a positive hadronic spectral density is employed to obtain upper bounds on the decay constants of $D$ and $D_s$ mesons. Including all known terms of the operator product expansion of this correlation function in QCD and taking into account the estimated uncertainties, we obtain $f_D<230\mathrm{MeV}$ and $f_{D_s}<270\mathrm{MeV}$. Comparison with the decay constants determined from $D\to l{\nu }_l$ and $D_s\to l{\nu }_l$ measurements reveals a tension between the bound and current experimental value of $f_{D_s}$.

We present a worldvolume effective action suitable for the study of the confined phase of a $(Dp,\overline{D}p)$ system at weak coupling. We identify the mechanism by which the fundamental string arises from this action as a confined electric flux string when the $Dp$ and the $\overline{D}p$ annihilate. We construct an explicit dual action, more suitable for the study of the strong coupling regime, and show that it realizes a generalized Higgs-Stückelberg phase for the (relative) $(p-2)$-form field dual to the (overall) Born-Infeld vector. This is the mechanism put forward by Yi and collaborators based on duality arguments in order to explain the breaking of the overall U(1) gauge group at strong coupling. Indeed, in our dual description the Goldstone boson is a $(p-3)$ form magnetically charged with respect to the overall Born-Infeld vector field. This indicates that the condensing tachyonic objects originate from open $D(p-2)$-branes stretched between the brane and the antibrane. Our results provide an explicit realization of the breaking of the overall U(1) gauge group perturbatively, in a way consistent with the duality symmetries of string theory.

We investigate various aspects of a proposal by Aharony and Kutasov [O. Aharony and D. Kutasov, Phys. Rev. D 78, 026005 (2008).] for the gravity dual of an open Wilson line in the Sakai-Sugimoto model or its noncompact version. In particular, we use their proposal to determine the effect of finite temperature, as well as background electric and magnetic fields, on the chiral symmetry breaking order parameter. We also generalize their prescription to more complicated worldsheets and identify the operators dual to such worldsheets.

In higher-dimensional gauge theory, we need energies with higher power terms of field strength in order to realize pointwise monopoles. We consider new models with higher power terms of field strength and extraordinary kinetic terms of the scalar field. Monopole charges are computed as integrals over spheres and they are related to mapping class degree. Hedgehog solutions are investigated in these models. Every differential equation for these solutions is Abel’s differential equation. A condition for the existence of a finite energy solution is shown. The spaces of 1-jets of these equations are defined as sets of zeros of polynomials. Those spaces can be interpreted as singular quartic surfaces in three-dimensional complex projective space.