Attempts to connect string theory with astrophysical observation are hampered by a jargon barrier, where an intimidating profusion of orientifolds, Kähler potentials, etc. dissuades cosmologists from attempting to work out the astrophysical observables of specific string theory solutions from the recent literature. We attempt to help bridge this gap by giving a pedagogical exposition with detailed examples, aimed at astrophysicists and high energy theorists alike, of how to compute predictions for familiar cosmological parameters when starting with a 10-dimensional string theory action. This is done by investigating inflation in string theory, since inflation is the dominant paradigm for how early universe physics determines cosmological parameters. We analyze three explicit string models from the recent literature, each containing an infinite number of vacuum solutions. Our numerical investigation of some natural candidate inflatons, the so-called “moduli fields,” fails to find inflation. We also find in the simplest models that, after suitable field redefinitions, vast numbers of these vacua differ only in an overall constant multiplying the effective inflaton potential, a difference which affects neither the potential’s shape nor its ability to support slow-roll inflation. This illustrates that even having an infinite number of vacua does not guarantee having inflating ones. This may be an artifact of the simplicity of the models that we study. Instead, more complicated string theory models appear to be required, suggesting that identifying the inflating subset of the string landscape will be challenging.

We study the formation of cosmic strings by confining a stochastic magnetic field into flux tubes in a numerical simulation. We use overdamped evolution in a potential that is minimized when the flux through each face in the simulation lattice is a multiple of the fundamental flux quantum. When the typical number of flux quanta through a correlation-length-sized region is initially about 1, we find a string network similar to that generated by the Kibble-Zurek mechanism. With larger initial flux, the loop distribution and the Brownian shape of the infinite strings remain unchanged, but the fraction of length in infinite strings is increased. A 2D slice of the network exhibits bundles of strings pointing in the same direction, as in earlier 2D simulations. We find, however, that strings belonging to the same bundle do not stay together in 3D for much longer than the correlation length. As the initial flux per correlation length is decreased, there is a point at which infinite strings disappear, as in the Hagedorn transition.

We study a model where two scalar fields, that are subdominant during inflation, decay into radiation some time after inflation has ended but before primordial nucleosynthesis. Perturbations of these two curvaton fields can be responsible for the primordial curvature perturbation. We write down the full nonlinear equations that relate the primordial perturbation to the curvaton perturbations on large scales, calculate the power spectrum of the primordial perturbation, and finally go to second order to find the nonlinearity parameter, $f_{\mathrm{NL}}$. We find large positive values of $f_{\mathrm{NL}}$ if the energy densities of the curvatons are subdominant when they decay, as in the single curvaton case. But we also find a large $f_{\mathrm{NL}}$ even if the curvatons dominate the total energy density in the case when the inhomogeneous radiation produced by the first curvaton decay is diluted by the decay of a second nearly homogeneous curvaton. The minimum value $\min (f_{\mathrm{NL}})=-5/4$ which we find is the same as in the single-curvaton case.

We follow the inspiral and merger of equal-mass black holes (BHs) by the moving puncture technique and demonstrate that both the exterior solution and the asymptotic gravitational waveforms are unchanged when the initial interior solution is replaced by constraint-violating junk initial data. We apply this result to evolve conformal thin-sandwich (CTS) binary BH initial data by filling their excised interiors with arbitrary, but smooth, initial data and evolving with standard puncture gauge choices. The waveforms generated for both puncture and filled-CTS initial data are remarkably similar, and there are only minor differences between irrotational and corotational CTS BH binaries. Even the interior solutions appear to evolve to the same constraint-satisfying solution at late times, independent of the initial data.

Recent advances in random matrix theory enable one to determine the pseudoscalar decay constant from the dependence of the eigenvalues of the valence Dirac operator on an imaginary isospin chemical potential. We perform a pilot test of this idea, from simulations with two flavors of dynamical overlap fermions.

We study the potential between static SU(4) sources using the model of thick center vortices. Such vortices are characterized by the center elements $z_1=\mathrm{i}$ and $z_2=z_1^2$. Fitting the ratios of string tensions to those obtained in Monte Carlo calculations of lattice QCD we get $f_2>f_1^2$, where $f_n$ is the probability that a vortex of type $n$ is piercing a plaquette. Because of $z_2=z_1^2$ vortices of type two are overlapping vortices of type one. Therefore, $f_2>f_1^2$ corresponds to the existence of an attractive force between vortices of type one.

Calculations of collinear correlation functions in perturbative QCD and soft-collinear effective theory require a prescription for subtracting soft or zero-bin contributions in order to avoid double counting the contributions from soft modes. At leading order in $\lambda$, where $\lambda$ is the soft-collinear effective theory expansion parameter, the zero-bin subtractions have been argued to be equivalent to convolution with soft Wilson lines. We give a proof of the factorization of naive collinear Wilson lines that is crucial for the derivation of the equivalence. We then check the equivalence by computing the non-Abelian two-loop mixed collinear-soft contribution to the jet function in the quark form factor. These results demonstrate the equivalence, which can be used to give a nonperturbative definition of the zero-bin subtraction at lowest order in $\lambda$.

Protons and antiprotons at collider energies are a source of high-energy Weizsäcker-Williams photons. This may open a possibility to study exclusive photoproduction of heavy vector mesons at energies much larger than possible at the HERA accelerator. Here we present a detailed investigation of the exclusive $J/\psi$ photoproduction in proton-proton (Relativistic Heavy Ion Collider, CERN LHC) and proton-antiproton (Tevatron) collisions. We calculate several differential distributions in $t_1$, $t_2$, $y$, $\varphi$, as well as transverse momentum distributions of $J/\psi$’s. We discuss correlations in the azimuthal angle between outgoing protons or proton and antiproton as well as in the $(t_1,t_2)$ space. Differently from electroproduction experiments, here both colliding beam particles can be a source of photons, and we find large interference terms in azimuthal-angle distributions in a broad range of rapidities of the produced meson. We also include the spin-flip parts in the electromagnetic vertices. We discuss the effect of absorptive corrections on various distributions. Interestingly, absorption corrections induce a charge asymmetry in rapidity distributions, and are larger for $pp$ reactions than for the $p\overline{p}$ case. The reaction considered here constitutes an important nonreduceable background in recently proposed searches for odderon exchange.

We study the physics potential of placing a far detector in the east coast of Korea, where the off-axis neutrino beam from J-PARC at Tokai village for the Tokai-to-Kamioka project has significant intensity at a few GeV range. In particular, we examine the capability of determining the mass hierarchy pattern and the $CP$ phase of the lepton-flavor-mixing matrix when a 100 kt water Čerenkov detector is placed at various locations in Korea for the off-axis beam (OAB) of 2.5° and 3.0° at the Super-Kamiokande site. The best results are found for a combination of 3.0° OAB at SK ($L=295\mathrm{km}$) and 0.5° OAB at $L=1000\mathrm{km}$, where the mass hierarchy pattern can be determined at $3\sigma$ level for ${sin}^{2}2{\theta }_{\mathrm{RCT}}\gtrsim 0.05$ (0.06) when the hierarchy is normal (inverted), after 5 yr of running ($5\times {10}^{21}\mathrm{POT}$). We also find that the leptonic $CP$ phase, ${\delta }_{\mathrm{MNS}}$, can be constrained uniquely, without invoking antineutrino beams, as long as the mass hierarchy pattern is determined. Those results are obtained by assuming that the charged current quasielastic events can be separated from the other backgrounds with high efficiency, the neutrino energy can be reconstructed with a hundred MeV uncertainty, and the earth matter density along the baseline can be determined with 3% accuracy.

Using $58\times {10}^6$ $J/\psi$ and $14\times {10}^6$ $\psi (2S)$ events collected by the BESII detector at the BEPC, branching fractions or upper limits for the decays $J/\psi$ and $\psi (2S)\to \Lambda \overline{\Lambda }{\pi }^0$ and $\Lambda \overline{\Lambda }\eta$ are measured. For the isospin violating decays, the upper limits are determined to be $\mathcal{B}(J/\psi \to \Lambda \overline{\Lambda }{\pi }^0)<6.4\times {10}^{-5}$ and $\mathcal{B}[\psi (2S)\to \Lambda \overline{\Lambda }{\pi }^0]<4.9\times {10}^{-5}$ at the 90% confidence level. The isospin conserving process $J/\psi \to \Lambda \overline{\Lambda }\eta$ is observed for the first time, and its branching fraction is measured to be $\mathcal{B}(J/\psi \to \Lambda \overline{\Lambda }\eta )=(2.62\pm 0.60\pm 0.44)\times {10}^{-4}$, where the first error is statistical and the second one is systematic. No $\Lambda \overline{\Lambda }\eta$ signal is observed in $\psi (2S)$ decays, and $\mathcal{B}[\psi (2S)\to \Lambda \overline{\Lambda }\eta ]<1.2\times {10}^{-4}$ is set at the 90% confidence level. Branching fractions of $J/\psi$ decays into ${\Sigma }^{+}{\pi }^{-}\overline{\Lambda }$ and ${\overline{\Sigma }}^{-}{\pi }^{+}\Lambda$ are also reported, and the sum of these branching fractions is determined to be $\mathcal{B}(J/\psi \to {\Sigma }^{+}{\pi }^{-}\overline{\Lambda }+\mathrm{c}.\mathrm{c}.)=(1.52\pm 0.08\pm 0.16)\times {10}^{-3}$.

Muon production at forward rapidity ($1.5\le |\eta |\le 1.8$) has been measured by the PHENIX experiment over the transverse momentum range $1\le p_T\le 3\mathrm{GeV}/c$ in $\sqrt{s}=200\mathrm{GeV}$ $p+p$ collisions at the Relativistic Heavy Ion Collider. After statistically subtracting contributions from light hadron decays an excess remains which is attributed to the semileptonic decays of hadrons carrying heavy flavor, i.e. charm quarks or, at high $p_T$, bottom quarks. The resulting muon spectrum from heavy flavor decays is compared to PYTHIA and a next-to-leading-order perturbative QCD calculation. PYTHIA is used to determine the charm quark spectrum that would produce the observed muon excess. The corresponding differential cross section for charm quark production at forward rapidity is determined to be $d{\sigma }_{c\overline{c}}/dy{|}_{y=1.6}=0.243\pm 0.013(\mathrm{stat}.)\pm 0.105(\mathrm{data}\mathrm{syst}.)\genfrac{}{}{0ex}{}{+0.049}{-0.087}(\mathrm{PYTHIA}\mathrm{syst}.)\mathrm{mb}$.

$SL(2,\mathbb{Z})$ duality transformations in asymptotically ${\mathrm{AdS}}_4\times S^7$ act nontrivially on the three-dimensional superconformal field theory of coincident M2-branes on the boundary. We show how $S$-duality acts away from the IR fixed point. We develop a systematic method to holographically obtain the deformations of the boundary CFT and show how electric-magnetic duality relates different deformations. We analyze in detail marginal deformations and deformations by dimension 4 operators. In the case of massive deformations, the renormalization group flow relates $S$-dual CFT’s. Correlation functions in the CFT are computed by varying magnetic bulk sources, whereas correlation functions in the dual CFT are computed by electric bulk sources. Under massive deformations, the boundary effective action is generically minimized by massive self-dual configurations of the $U(1)$ gauge field. We show that a self-dual choice of boundary conditions exists, and it corresponds to the self-dual topologically massive gauge theory in $2+1$ dimensions. Thus, self-duality in three dimensions can be understood as a consequence of electric-magnetic invariance in the bulk of ${\mathrm{AdS}}_4$.

Recently a model, which is equivalent to the scalar form of a Gürsey model, is shown to be a nontrivial field theoretical model when it is gauged with a $SU(N)$ field. In this paper we study another model that is equivalent to the vector form of the Gürsey model. We get a trivial theory when it is coupled with a scalar field. This result changes drastically when it is coupled with an additional $SU(N)$ field. We find a nontrivial field theoretical model under certain conditions.

We investigate unparticle physics with supersymmetry (SUSY). The SUSY breaking effects due to the gravity mediation induce soft masses for the SUSY unparticles and hence break the conformal invariance. The unparticle physics observable in near future experiments is only consistent if the SUSY breaking effects from the hidden sector to the standard model sector are dominated by the gauge mediation, or if the SUSY breaking effects to the unparticle sector are sufficiently sequestered. We argue that the natural realization of the latter possibility is the conformal sequestering scenario.

We consider gauge theories with scalar matter with and without supersymmetry at nonzero chemical potential. It is argued that a chemical potential plays a role similar to the Fayet-Iliopoulos term. We analyze theory at the weak coupling regime at large chemical potential and argue that it supports non-Abelian non-Bogomol’nyi-Prasad-Sommerfield strings. World sheet theory on the non-Abelian string in a dense matter is briefly discussed.

The planned Laser Interferometer Space Antenna (LISA) is expected to detect the inspiral and merger of massive black hole binaries (MBHBs) at $z\lesssim 5$ with signal-to-noise ratios (SNRs) of hundreds to thousands. Because of these high SNRs, and because these SNRs accrete over periods of weeks to months, it should be possible to extract the physical parameters of these systems with high accuracy; for instance, for a $\sim {10}^6{M}_{\odot }$ MBHBs at $z=1$ it should be possible to determine the two masses to $\sim 0.1\%$ and the sky location to $\sim 1°$. However, those are just the errors due to noise: there will be additional “theoretical” errors due to inaccuracies in our best model waveforms, which are still only approximate. The goal of this paper is to estimate the typical magnitude of these theoretical errors. We develop mathematical tools for this purpose, and apply them to a somewhat simplified version of the MBHB problem, in which we consider just the inspiral part of the waveform and neglect spin-induced precession, eccentricity, and PN amplitude corrections. For this simplified version, we estimate that theoretical uncertainties in sky position will typically be $\sim 1°$, i.e., comparable to the statistical uncertainty. For the mass and spin parameters, our results suggest that while theoretical errors will be rather small absolutely, they could still dominate over statistical errors (by roughly an order of magnitude) for the strongest sources. The tools developed here should be useful for estimating the magnitude of theoretical errors in many other problems in gravitational-wave astronomy.

We consider the hypothesis that dark energy and dark matter are the two faces of a single dark component, a unified dark matter (UDM) that we assume can be modeled by the affine equation of state (EoS) $P=p_0+\alpha \rho$, resulting in an effective cosmological constant ${\rho }_{\Lambda }=-p_0/(1+\alpha )$. The affine EoS arises from the simple assumption that the speed of sound is constant; it may be seen as an approximation to an unknown barotropic EoS $P=P(\rho )$, and may as well represent the tracking solution for the dynamics of a scalar field with appropriate potential. Furthermore, in principle the affine EoS allows the UDM to be phantom. We constrain the parameters of the model, $\alpha$ and ${\Omega }_{\Lambda }$, using data from a suite of different cosmological observations, and perform a comparison with the standard $\Lambda \mathrm{CDM}$ model, containing both cold dark matter and a cosmological constant. First considering a flat cosmology, we find that the UDM model with affine EoS fits the joint observations very well, better than $\Lambda \mathrm{CDM}$, with best-fit values $\alpha =0.01\pm 0.02$ and ${\Omega }_{\Lambda }=0.70\pm 0.04$ (95% confidence intervals). The standard model (best-fit ${\Omega }_{\Lambda }=0.71\pm 0.04$), having one less parameter, is preferred by a Bayesian model comparison. However, the affine EoS is at least as good as the standard model if a flat curvature is not assumed as a prior for $\Lambda \mathrm{CDM}$. For the latter, the best-fit values are ${\Omega }_K=-{0.02}_{-0.02}^{+0.01}$ and ${\Omega }_{\Lambda }=0.71\pm 0.04$, i.e. a closed model is preferred. A phantom UDM with affine EoS is ruled out well beyond $3\sigma$.

In this paper I present the detail estimations for the width of the 511 keV line produced by a mechanism when dark matter is represented by macroscopically large dense nuggets. I argue that the width of 511 keV emission in this mechanism is very narrow (in a few keV range) in agreement with all observations. The dominant mechanism of the annihilation in this case is the positronium formation $e^{+}{e}^{-}\to {}^{1}S_0\to 2\gamma$ rather than a direct $e^{+}{e}^{-}\to 2\gamma$ annihilation. I also discuss some generic features of the $\gamma$ rays spectrum (in few MeV range) resulting from this mechanism.

During a core-collapse supernova, absorption of ${\overline{\nu }}_e$ emitted from the protoneutron star by protons in the hydrogen envelope produces neutrons and positrons. Neutron capture on protons and positron annihilation then produce $\gamma$ rays of 2.22 and 0.511 MeV, respectively. We calculate the fluxes of these $\gamma$ rays expected from a supernova with an $11M_{\odot }$ progenitor. The flux from neutron capture on protons exponentially decays on a time scale of 564 s, which is determined by neutron decay and capture on protons and ${}^3\mathrm{He}$ nuclei. The peak flux is $2.38\times {10}^{-7}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ for a supernova at a distance of 1 kpc. In contrast, the $\gamma$-ray flux from positron annihilation follows the time evolution of the ${\overline{\nu }}_e$ luminosity and lasts for $\sim 10\mathrm{s}$. The peak flux in this case is $6.8\times {10}^{-5}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ for a supernova at a distance of 1 kpc. Detection of the above $\gamma$-ray fluxes is beyond the capability of current instruments, and perhaps even those planned for the near future. However, if such fluxes can be detected, they not only constitute a new kind of signal that occurs during the gap of several hours between the neutrino signals and the optical display of a supernova, but may also provide a useful probe of the conditions in the surface layers of the supernova progenitor.

We study the response of a stochastic FitzHugh-Nagumo model to weak external forcing with the aim of implementing a nonlinear algorithm, devised for the robust detection of transient signals such as gravitational wave bursts. In order to test the performance of the algorithm, we exploited the ensemble of maximum entropy signals—known as chirplets. In particular, we investigated the chirplet parameter subspace representing the gravitational wave bursts within range of nowadays interferometric detectors. We found that the false alarm rate can be controlled by changing the constant term in the equation of the slow variable while the detection efficiency is completely insensitive to the kind of injected chirplet. The receiver operating characteristic curves have been evaluated and compared with the performance of power detectors (threshold crossing of local power), which are commonly used for the burst detection.