We construct a Green-Schwarz (GS) light-cone closed superstring theory from the type IIB matrix model. A GS light-cone string action is derived from the two-dimensional $\mathcal{N}=8U(n)$ noncommutative Yang-Mills (NCYM) theory by identifying a noncommutative scale with a string scale. The supersymmetry transformation for the light-cone gauge action is also derived from supersymmetry transformation for the IIB matrix model. By identifying the physical states and interaction vertices, string theory is perturbatively reproduced.

Puff field theories (PFT) arise as the decoupling limits of D3 branes in a Melvin universe and exhibit spatially nonlocal dynamics. Unlike other realizations of nonlocality in string theory, PFTs have full $SO(3)$ rotational symmetry. In this work, we analyze the strongly coupled regime of a PFT through gravitational holography. We find a novel mechanism at the heart of the phenomenon of nonlocality: a quantum entanglement of UV and IR dynamics. In the holographic bulk, this translates to an apparent horizon splitting the space into two regions—with the UV completion of the PFT sitting at the horizon. We unravel this intricate UV-IR setting and devise a prescription for computing correlators that extends the original dictionary of holographic renormalization group. We then implement a cosmological scenario where PFT correlators set the initial conditions for primordial fluctuations. We compute the associated power spectrum of the cosmic microwave background and find that the scenario allows for a distinct stringy signature.

Motivated by recent interest in understanding properties of strongly magnetized matter, we study the dynamical electron mass generated through approximate chiral symmetry breaking in QED in a strong magnetic field. We reliably calculate the dynamical electron mass by numerically solving the nonperturbative Schwinger-Dyson equations in a consistent truncation within the lowest Landau level approximation. It is shown that the generation of dynamical electron mass in a strong magnetic field is significantly enhanced by the perturbative electron mass that explicitly breaks chiral symmetry in the absence of a magnetic field.

The functional approach to Coulomb gauge Yang-Mills theory is considered within the standard, second order, formalism. The Dyson-Schwinger equations and Slavnov-Taylor identities concerning the two-point functions are derived explicitly and one-loop perturbative results are presented.

We consider the existence and stability of static configurations of a scalar field in a five dimensional spacetime in which the extra spatial dimension is compactified on an $S^1/Z_2$ orbifold. For a wide class of potentials with multiple minima there exist a finite number of such configurations, with total number depending on the size of the orbifold interval. However, a Sturm-Liouville stability analysis demonstrates that all such configurations with nodes in the interval are unstable. Nodeless static solutions, of which there may be more than one for a given potential, are far more interesting, and we present and prove a powerful general criterion that allows a simple determination of which of these nodeless solutions are stable. We demonstrate our general results by specializing to a number of specific examples, one of which may be analyzed entirely analytically.

This is the sixth paper in the series developing the formalism to manage the effective scattering theory of strong interactions. Relying on the theoretical scheme suggested in our previous publications we concentrate here on the practical aspect and apply our technique to the elastic pion-nucleon scattering amplitude. We test numerically the $\pi N$ spectrum sum rules that follow from the tree-level bootstrap constraints. We show how these constraints can be used to estimate the tensor and vector $NN\rho$ coupling constants. Last, we demonstrate that the tree-level low-energy expansion coefficients computed in the framework of our approach show a nice agreement with known experimental data. These results allow us to claim that the extended perturbation scheme is quite reasonable from the computational point of view.

Boltzmann equations are often used to describe the nonequilibrium time-evolution of many-body systems in particle physics. Prominent examples are the computation of the baryon asymmetry of the universe and the evolution of the quark-gluon plasma after a relativistic heavy ion collision. However, Boltzmann equations are only a classical approximation of the quantum thermalization process, which is described by so-called Kadanoff-Baym equations. This raises the question how reliable Boltzmann equations are as approximations to the complete Kadanoff-Baym equations. Therefore, we present in this article a detailed comparison of the Boltzmann and the Kadanoff-Baym equations in the framework of a chirally invariant Yukawa-type quantum field theory including fermions and scalars. The obtained numerical results reveal significant differences between both types of equations. Apart from quantitative differences, on a qualitative level the late-time universality respected by the Kadanoff-Baym equations is severely restricted in the case of the Boltzmann equations. Furthermore, the Kadanoff-Baym equations strongly separate the time scales between kinetic and chemical equilibration. In contrast to this standard Boltzmann equations cannot describe the process of quantum-chemical equilibration, and consequently also cannot feature the above separation of time scales.

A nontrivial interplay of the UV and IR scaling laws, a generalization of the universality is demonstrated in the framework of the massive sine-Gordon model, as a result of a detailed study of the global behavior of the renormalization group flow and the phase structure.

Rotating charged Gauss-Bonnet black hole solutions in higher dimensional ($d>4$), asymptotically anti-de Sitter spacetime are obtained in the small angular momentum limit. The angular momentum, magnetic dipole moment, and the gyromagnetic ratio of the black holes are calculated and it turns out that the Gauss-Bonnet term does not affect the gyromagnetic ratio.

The renormalized mean value of the quantum Lagrangian and the corresponding components of the energy-momentum tensor for massive spinor fields coupled to an arbitrary gravitational field configuration having cylindrical symmetry are analytically evaluated using the Schwinger-DeWitt approximation, up to second order in the inverse mass value. The general results are employed to explicitly derive compact analytical expressions for the quantum mean Lagrangian and Energy-Momentum tensor in the particular background of the black-string spacetime.

We continue the program of constructing, within the effective-one-body (EOB) approach, high-accuracy, faithful analytic waveforms describing the gravitational wave signal emitted by inspiralling and coalescing binary black holes. We present the comparable-mass version of a new, resummed 3 post-Newtonian (PN) accurate EOB quadrupolar waveform that we recently introduced in the small-mass-ratio limit. We compare the phase and the amplitude of this waveform to the recently published results of a high-accuracy numerical simulation of 15 orbits of an inspiralling equal-mass binary black hole system performed by the Caltech-Cornell group. We find a remarkable agreement, both in phase and in amplitude, between the new EOB waveform and the published numerical data. More precisely: (i) in the gravitational wave (GW) frequency domain $M\omega <0.08$ where the phase of one of the nonresummed “Taylor approximant” (T4) waveform matches well with the numerical relativity one, we find that the EOB phase fares as well, while (ii) for higher GW frequencies, $0.08<M\omega \lesssim 0.14$, where the Taylor T4 approximant starts to significantly diverge from the numerical relativity phase, we show that the EOB phase continues to match well the numerical relativity one. We further propose various methods of tuning the two inspiral flexibility parameters, $a_5$ and $v_{\mathrm{pole}}$, of the EOB waveform so as to “best fit” EOB predictions to numerical data. We find that the maximal dephasing between EOB and numerical relativity can then be reduced below ${10}^{-3}$ GW cycles over the entire span (30 GW cycles) of the simulation (while, without tuning them, the dephasing is $<8\times {10}^{-3}$ cycles). In addition, our resummed EOB amplitude agrees much better with the numerical relativity one than any of the previously considered nonresummed, post-Newtonian one (including a recently derived, nonresummed 3 PN-accurate one). We think that the present work, taken in conjunction with other recent works on the EOB–numerical relativity comparison confirms the ability of the EOB formalism (especially in its recently improved avatars) to faithfully capture the “real” general relativistic waveforms.

We construct exact nonstatic nonhomogeneous spherically symmetric solutions in the theory of gravity with a scalar field possessing the exponential potential. The solution of particular interest corresponds to the scalar field with negative kinetic energy, i.e. a ghost, and represents two asymptotically homogeneous spatially flat universes connected by a throat. We interpret this solution as a wormhole in the cosmological setting. Both the universes and the wormhole throat are simultaneously expanding with acceleration. The character of expansion qualitatively depends on the wormhole’s mass $m$. For $m=0$ the expansion goes exponentially, so that the corresponding spacetime configuration represents two de Sitter universes joining by the throat. For $m>0$ the expansion has the power character, so that one has the inflating wormhole connecting two homogeneous spatially flat universes expanding according to the power law into the final singularity. The stability analysis of the nonstatic wormholes reveals their instability against linear spherically symmetric perturbations.

We determine the full post-Newtonian limit of theories of gravity that extend general relativity by replacing the Ricci scalar, $R$, in the generating Lagrangian by some analytic function, $f(R)$. We restrict ourselves to theories that admit Minkowski space as a suitable background, and perform a perturbative expansion in the manner prescribed by the parametrized post-Newtonian formalism. Extra potentials are found to be present that are not accounted for in the usual treatment, and a discussion is provided on how they may be used to observationally distinguish these theories from general relativity at the post-Newtonian level.

We study the cosmological evolution of a tachyon scalar field $T$ with a Dirac-Born-Infeld type Lagrangian and potential $V(T)$ coupled to a canonically normalized scalar field $\varphi$ with an interaction term $B(T,\varphi )$ in the presence of a barotropic fluid ${\rho }_b$, which can be matter or radiation. The force between the barotropic fluid and the scalar fields is only gravitational. We show that the dynamics is completely determined by only three parameters ${\lambda }_1=-V_T/V^{3/2}$, ${\lambda }_2=-B_T/B^{3/2}$, and ${\lambda }_3=-B_{\varphi }/B$. We determine analytically the conditions for ${\lambda }_i$ under which the energy density of $T$, $\varphi$, and ${\rho }_b$ have the same redshift. We study the behavior of $T$ and $\varphi$ in the asymptotic limits for $\lambda$ and we show the numerical solution for different interesting cases. The effective equation of state for the tachyon field changes due to the interaction with the scalar field and we show that it is possible for a tachyon field to redshift as matter in the absence of an interaction term $B$ and as radiation when $B$ is turned on. This result solves then the tachyonic matter problem.

The creation of large scale magnetic fields is studied in an inflationary universe where electrodynamics is assumed to be nonlinear. After inflation ends electrodynamics becomes linear and thus the description of reheating and the subsequent radiation dominated stage are unaltered. The nonlinear regime of electrodynamics is described by Lagrangians having a power-law dependence on one of the invariants of the electromagnetic field. It is found that there is a range of parameters for which primordial magnetic fields of cosmologically interesting strengths can be created.

We calculate the yield of high energy neutrinos produced in astrophysical sources for arbitrary interaction depths ${\tau }_0$ and magnetic field strengths $B$. We take into account energy loss processes like synchrotron radiation and diffusion of charged particles in turbulent magnetic fields as well as the scattering of secondaries on background photons and the direct production of charm neutrinos. Meson-photon interactions are simulated with an extended version of the SOPHIA model. Diffusion leads to an increased path length before protons leave the source of size $R_s$ and therefore magnetized sources lose their transparency below the energy $E\sim {10}^{18}\mathrm{eV}(R_s/\mathrm{pc})(B/\mathrm{mG}){\tau }_0^{1/\alpha }$, with $\alpha =1/3$ and 1 for Kolmogorov and Bohm diffusion, respectively. Moreover, the neutrino flux is suppressed above the energy where synchrotron energy losses become important for charged particles. As a consequence, the energy spectrum and the flavor composition of neutrinos are strongly modified both at low and high energies even for sources with ${\tau }_0\lesssim 1$.

We study the effect of WIMP annihilation on the temperature of a neutron star. We shall argue that the released energy due to WIMP annihilation inside the neutron stars might affect the temperature of stars older than $10\times {10}^6\mathrm{\text{years}}$, flattening out the temperature at $\sim {10}^4\mathrm{K}$ for a typical neutron star.

Various experiments indicate the existence of a second knee around energy $E=3\times {10}^{17}\mathrm{eV}$ in the cosmic ray spectrum. This feature could be the signature of the end of the galactic component and of the emergence of the extragalactic one, provided that the latter cuts off at low energies. Recent analytical calculations have shown that this cutoff could be a consequence of the existence of extragalactic magnetic fields (Refs. [M. Lemoine, Phys. Rev. D 71, 083007 (2005).][R. Aloisio and V. Berezinsky, Astrophys. J. 625, 249 (2005).]): low energy protons diffuse on extragalactic magnetic fields and cannot reach the observer within a given time. We study the influence of inhomogeneous magnetic fields on the magnetic horizon, using a new semianalytical propagation code. Our results indicate that, at a fixed value of the volume averaged magnetic field $⟨B⟩$, the amplitude of the low energy cutoff is mainly controlled by the strength of magnetic fields in the voids of the large-scale structure distribution.

Recently, observational searches for gravitational wave background (GWB) have been developed and given direct and indirect constraints on the energy density of GWB in a broad range of frequencies. These constraints have already rejected some theoretical models of large GWB spectra. However, at 100 MHz, there is no strict upper limit from direct observation, though the indirect limit by ${}^2\mathrm{He}$ abundance due to big-bang nucleosynthesis exists. In this paper, we propose an experiment with laser interferometers searching GWB at 100 MHz. We considered three detector designs and evaluated the GW response functions of a single detector. As a result, we found that, at 100 MHz, the most sensitive detector is the design, a so-called synchronous recycling interferometer, which has better sensitivity than an ordinary Fabry-Perot Michelson interferometer by a factor of 3.3 at 100 MHz. When we select the arm length of 0.75 m and realistic optical parameters, the best sensitivity achievable is $h\approx 7.8\times {10}^{-21}{\mathrm{Hz}}^{-1/2}$ at 100 MHz with bandwidth $\sim 2\mathrm{kHz}$.

The associated production of a Higgs boson with a $b$ quark is a discovery mode for a minimal supersymmetric standard model (MSSM) Higgs boson at large $\tan \beta$. We compute the SUSY QCD corrections from gluino and squark loops to this process and combine them with the $\mathcal{O}({\alpha }_s^2)$ next-to-leading order (NLO) QCD corrections to obtain reliable predictions for the rate. Finally, we compare our results with an effective Lagrangian approximation which includes only the low energy corrections from squark and gluino loops to the $b\overline{b}$ Higgs vertices.