The distribution of the gluon action density in mesonic systems is investigated at finite temperature. The simulations are performed in quenched QCD for two temperatures below the deconfinement phase. Unlike the gluonic profiles displayed at $T=0$, the action-density isosurfaces display a prolate-spheroid-like shape. The curved width profile of the flux tube is found to be consistent with the prediction of the free bosonic string model at large distances.

We study how leptogenesis can be implemented in a seesaw model with $S_4$ flavor symmetry, which leads to the neutrino tribimaximal mixing matrix and degenerate right-handed (RH) neutrino spectrum. Introducing a tiny soft $S_4$ symmetry breaking term in the RH neutrino mass matrix, we show that the flavored resonant leptogenesis can be successfully realized, which can lower the seesaw scale much so, as to make it possible to probe in colliders. Even though such a tiny soft breaking term is essential for leptogenesis, it does not significantly affect the low-energy observables. We also investigate how the effective light neutrino mass $|⟨m_{ee}⟩|$ associated with neutrinoless double beta decay can be predicted along with the neutrino mass hierarchies by imposing experimental data of low-energy observables. We find a direct link between leptogenesis and neutrinoless double beta decay characterized by $|⟨m_{ee}⟩|$ through a high energy $CP$ phase $\varphi$, which is correlated with low-energy Majorana $CP$ phases. It is shown that our predictions of $|⟨m_{ee}⟩|$ for some fixed parameters of high energy physics can be constrained by the current observation of baryon asymmetry.

We consider a string-inspired nonsupersymmetric extension of the standard model with gauged anomalous $U(1)$ flavor symmetries. Consistency requires the Green-Schwarz (GS) mechanism to cancel mixed anomalies. The additional required scalars provide Stückelberg masses for the $Z^{\prime }$ particles associated to the gauged flavor symmetry, so they decouple at low energies. Our models also include a complex scalar field $\varphi$ to generate Froggatt-Nielsen mass terms for light particles, giving a partial solution to the fermion mass problem. A residual approximate (anomalous) global symmetry survives at low energies. The associated pseudo-Goldstone mode is the phase of the $\varphi$ scalar field, and it becomes the dominant contribution to the physical axion. An effective field theory analysis that includes neutrino masses gives a prediction for the axion decay constant. We find a simple model where the axion decay constant is in the center of the allowed window.

We consider a six-dimensional brane world model, where the brane is described by a localized solution to the baby-Skyrme model extending in the extra dimensions. The branes have a cosmological constant modeled by inflating four-dimensional slices, and we further consider a bulk cosmological constant. We construct solutions numerically and present evidence that the solutions cease to exist for large values of the brane cosmological constant in some particular case. Then we study the stability of the model by considering perturbation of the gravitational part (resp. baby Skyrmion) with fixed matter fields (resp. gravitational background). Our results indicate that the perturbation equations do not admit localized solutions for certain type of perturbation. The stability analysis can be alternatively seen as leading to a particle spectrum; we give mass estimations for the baby-Skyrme perturbation and for the graviton.

It is usually believed that there are no perturbative anomalies in supersymmetric gauge theories beyond the well-known chiral anomaly. In this paper we revisit this issue, because previously given arguments are incomplete. Specifically, we rule out the existence of soft anomalies, i.e., quantum violations of supersymmetric Ward identities proportional to a mass parameter in a classically supersymmetric theory. We do this by combining a previously proven theorem on the absence of hard anomalies with a spurion analysis, using the methods of algebraic renormalization. We work in the on-shell component formalism throughout. In order to deal with the nonlinearity of on-shell supersymmetry transformations, we take the spurions to be dynamical, and show how they nevertheless can be decoupled.

A gedanken experiment in which a black hole is pushed to spin at its maximal rate by tossing into it a test body is considered. After demonstrating that this is kinematically possible for a test body made of reasonable matter, we focus on its implications for black hole thermodynamics and the apparent violation of the third law (unattainability of the extremal black hole). We argue that this is not an actual violation, due to subtleties in the absorption process of the test body by the black hole, which are not captured by the purely kinematic considerations.

Higher dimensional black holes play an exciting role in fundamental physics, such as high energy physics. In this paper, we use the formalism and numerical code reported in [1] to study the head-on collision of two black holes. For this purpose we provide a detailed treatment of gravitational wave extraction in generic $D$ dimensional space-times, which uses the Kodama-Ishibashi formalism. For the first time, we present the results of numerical simulations of the head-on collision in five space-time dimensions, together with the relevant physical quantities. We show that the total radiated energy, when two black holes collide from rest at infinity, is approximately $(0.089\pm 0.006)\%$ of the center of mass energy, slightly larger than the 0.055% obtained in the four-dimensional case, and that the ringdown signal at late time is in very good agreement with perturbative calculations.

We consider the problem of the renormalization of the vacuum polarization in a symmetry space-time with axial but not spherical symmetry, Schwarzschild space-time threaded by an infinite straight cosmic string. Unlike previous calculations, our framework to compute the renormalized vacuum polarization does not rely on special properties of Legendre functions, but rather has been developed in a way that we expect to be applicable to Kerr space-time.

We study the effects of noncommutativity, in the form of a Lie-algebraically deformed Poisson commutation relations, on the evolution of a Bianchi type I cosmological model with a positive cosmological constant. The phase space variables turn out to correspond to the scale factors of this model in $x$, $y$, and $z$ directions. According to the conditions that the structure constants (deformation parameters) should satisfy, we argue that there are two types of noncommutative phase space with Lie-algebraic structure. The exact classical solutions in commutative and type I noncommutative cases are presented. In the framework of this type of deformed phase space, we investigate the possibility of building a Bianchi I model with cyclic scale factors in which the size of the Universe in each direction experiences an endless sequence of contractions and reexpansions. We also obtain some approximate solutions for the type II noncommutative structure by numerical methods and show that the cyclic behavior is repeated as well. These results are compared with the standard commutative case, and similarities and differences of these solutions are discussed.

We examine the extent to which the self-annihilation of supersymmetric neutralino dark matter, as well as light dark matter, influences the rate of heating, ionization, and Lyman-$\alpha$ pumping of interstellar hydrogen and helium and the extent to which this is manifested in the 21 cm global background signal. We fully consider the enhancements to the annihilation rate from dark matter halos and substructures within them. We find that the influence of such structures can result in significant changes in the differential brightness temperature, $\delta T_b$. The changes at redshifts $z<25$ are likely to be undetectable due to the presence of the astrophysical signal; however, in the most favorable cases, deviations in $\delta T_b$, relative to its value in the absence of self-annihilating dark matter, of up to $\simeq 20\mathrm{mK}$ at $z=30$ can occur. Thus we conclude that, in order to exclude these models, experiments measuring the global 21 cm signal, such as EDGES and CORE, will need to reduce the systematics at 50 MHz to below 20 mK.

In Lyman-$\alpha$ forest measurements it is generally assumed that quasars are mere background light sources which are uncorrelated with the forest. Gravitational lensing of the quasars violates this assumption. This effect leads to a measurement bias, but more interestingly it provides a valuable signal. The lensing signal can be extracted by correlating quasar magnitudes with the flux-power spectrum and with the flux decrement. These correlations will be challenging to measure but their detection provides a direct measure of how features in the Lyman-$\alpha$ forest trace the underlying mass density field. Observing them will test the fundamental hypothesis that fluctuations in the forest are predominantly driven by fluctuations in mass, rather than in the ionizing background, helium reionization, or winds. We discuss ways to disentangle the lensing signal from other sources of such correlations, including dust, continuum, and background residuals. The lensing-induced measurement bias arises from sample selection: one preferentially collects spectra of magnified quasars which are behind overdense regions. This measurement bias is $\sim 0.1–1\%$ for the flux-power spectrum, optical depth, and the flux probability distribution. Since the effect is systematic, quantities such as the amplitude of the flux-power spectrum averaged across scales should be interpreted with care.

One of the important goals for future neutrino telescopes is to identify the flavors of astrophysical neutrinos and therefore determine the flavor ratio. The flavor ratio of astrophysical neutrinos observed on the Earth depends on both the initial flavor ratio at the source and flavor transitions taking place during propagations of these neutrinos. We propose a model independent parametrization for describing the above flavor transitions. A few flavor transition models are employed to test our parametrization. The observational test for flavor transition mechanisms through our parametrization is discussed.

We show how the peak-background split (PBS) can be generalized to predict the effect of nonlocal primordial non-Gaussianity on the clustering of halos. Our approach is applicable to arbitrary primordial bispectra. We show that the scale dependence of halo clustering predicted in the peak-background split agrees with that of the local-biasing model on large scales. On smaller scales, $k\gtrsim 0.01h{\mathrm{Mpc}}^{-1}$, the predictions diverge, a consequence of the assumption of separation of scales in the peak-background split. Even on large scales, PBS and local biasing do not generally agree on the amplitude of the effect outside of the high-peak limit. The scale dependence of the biasing—the effect that provides strong constraints to the local-model bispectrum—is far weaker for the equilateral and self-ordering-scalar-field models of non-Gaussianity. The bias scale dependence for the orthogonal and folded models is weaker than in the local model ($\sim k^{-1}$), but likely still strong enough to be constraining. We show that departures from scale-invariance of the primordial power spectrum may lead to order-unity corrections, relative to predictions made assuming scale-invariance—to the non-Gaussian bias in some of these nonlocal models for non-Gaussianity. An Appendix shows that a nonlocal model can produce the local-model bispectrum, a mathematical curiosity we uncovered in the course of this investigation.

We report the results of the first search for gravitational waves from compact binary coalescence using data from the Laser Interferometer Gravitational-Wave Observatory and Virgo detectors. Five months of data were collected during the Laser Interferometer Gravitational-Wave Observatory’s S5 and Virgo’s VSR1 science runs. The search focused on signals from binary mergers with a total mass between 2 and $35M_{\odot }$. No gravitational waves are identified. The cumulative 90%-confidence upper limits on the rate of compact binary coalescence are calculated for nonspinning binary neutron stars, black hole-neutron star systems, and binary black holes to be $8.7\times {10}^{-3}{\mathrm{yr}}^{-1}{\mathrm{L}}_{10}^{-1}$, $2.2\times {10}^{-3}{\mathrm{yr}}^{-1}{\mathrm{L}}_{10}^{-1}$, and $4.4\times {10}^{-4}{\mathrm{yr}}^{-1}{\mathrm{L}}_{10}^{-1}$, respectively, where ${\mathrm{L}}_{10}$ is ${10}^{10}$ times the blue solar luminosity. These upper limits are compared with astrophysical expectations.

In simulations with dynamical quarks it has been established that the ground state $\rho$ in the infrared is a strong mixture of the two chiral representations $(0,1)+(1,0)$ and $(1/2,1/2{)}_b$. Its angular momentum content is approximately the ${}^{3}S_1$ partial wave. Effective chiral restoration in an excited $\rho$-meson would require that in the infrared this meson couples predominantly to one of the two representations. The variational method allows one to study the mixing of interpolators with different chiral transformation properties in the nonperturbatively determined excited state at different resolution scales. We present results for the first excited state of the $\rho$-meson using simulations with $n_f=2$ dynamical quarks. We point out, that in the infrared a leading contribution to ${\rho }^{\prime }=\rho (1450)$ comes from $(1/2,1/2{)}_b$, in contrast to the $\rho$. The ${\rho }^{\prime }$ wave function contains a significant contribution of the ${}^{3}D_1$ wave which is not consistent with the quark model prediction.

We investigate the viability of Affleck-Dine baryogenesis in $D=4$, $N=1$ supergravity descending from string theory. The process relies on an initial condition where visible sector supersymmetric flat directions obtain tachyonic masses during inflation. We discuss this condition for a variety of cases where supersymmetry is broken during inflation by a geometric modulus or hidden sector scalar, and outline scenarios where the initial condition is satisfied.

We present high statistics results for the structure of the nucleon from a mixed-action calculation using $2+1$ flavors of asqtad sea and domain-wall valence fermions. We perform extrapolations of our data based on different chiral effective field theory schemes and compare our results with available information from phenomenology. We discuss vector and axial form factors of the nucleon, moments of generalized parton distributions, including moments of forward parton distributions, and implications for the decomposition of the nucleon spin.

We discuss the importance of inelasticity in the $P$-wave $\pi \pi$ amplitude on the Dalitz distribution of $3\pi$ events in $J/\psi$ decay. The inelasticity, which becomes sizable for $\pi \pi$ masses above 1.4 GeV, is attributed to $K\overline{K}\to \pi \pi$ rescattering. We construct an analytical model for the two-channel scattering amplitude and use it to solve the dispersion relation for the isobar amplitudes that parametrize the $J/\psi$ decay. We present comparisons between theoretical predictions for the Dalitz distribution of $3\pi$ events with available experimental data.

The transversity form factors of the pion, involving matrix elements of bilocal tensor currents, are evaluated in chiral quark models, both in the local Nambu-Jona-Lasinio with the Pauli-Villars regularization, as well as in nonlocal models involving momentum-dependent quark mass. After suitable QCD evolution, the agreement with recent lattice calculations is very good, in accordance to the fact that the spontaneously broken chiral symmetry governs the dynamics of the pion. Meson dominance of form factors with expected meson masses also works properly, conforming to the parton-hadron duality in the considered process.