We study the effect of curvaton decay on the primordial power spectrum. Using analytical approximations and also numerical calculations, we find that the power spectrum is enhanced during the radiation dominated era after the curvaton decay. The amplitude of the Bardeen potential is controlled by the fraction of the energy density in the curvaton at the time of curvaton decay. We show that the enhancement in the amplitude of the primordial curvature perturbation is, however, not large enough to lead to primordial black hole overproduction on scales which reenter the horizon after the time of curvaton decay.

We consider a generalized Thirring model in $0+1$ dimensions at finite density. In order to deal with the resulting sign problem we employ stochastic quantization, i.e., a complex Langevin evolution. We investigate the convergence properties of this approach and check in which parameter regions complex Langevin evolutions are applicable in this setting. To this end we derive numerous analytical results and compare directly with numerical results. In addition we employ indirect indicators to check for correctness. Finally, we interpret and discuss our findings.

We investigate the unpolarized pion and kaon fragmentation functions using the nonlocal chiral-quark model. In this model the interactions between the quarks and pseudoscalar mesons is manifested nonlocally. In addition, the explicit flavor SU(3) symmetry breaking effect is taken into account in terms of the current quark masses. The results of our model are evaluated to higher $Q^2$ value $Q^2=4{\mathrm{GeV}}^2$ by the QCD evolution. Then we compare them with the empirical parametrizations. We find that our results are in relatively good agreement with the empirical parametrizations and the other theoretical estimations.

More evidence has now been collected at the Large Hadron Collider suggesting the new 125–126 GeV boson is likely the long-sought Higgs boson in the standard model. One pressing question theorists continue to ask is whether this Higgs boson is a lone player responsible for the full electroweak symmetry breaking. Current data still allow room for additional Higgs bosons or some other UV physics that may play a partial role in electroweak symmetry breaking as well. We use the $WW$ scattering to investigate such a possibility, using the two-Higgs-doublet model as a prototype. The $WW$ scattering becomes strong when the extra Higgs bosons are very heavy. We study the sensitivity of these strong $WW$ scattering signals at the 13 TeV Large Hadron Collider.

We consider multi-Galileon theory, the most general Galilean invariant theory with $N$ scalar fields linearly coupled to the trace of the stress-energy tensor. We study the behavior of perturbations on a static spherically symmetric background with a massive point source, and show that, under the assumptions of stability and successful Vainshtein screening, solutions cannot be found that are free of both superluminal propagation and slowly moving, strongly coupled fluctuations. The latter imply that the theoretical and phenomenological issues related to a very low strong-interaction scale cannot be avoided in this model.

We calculate the two-loop pressure of a plasma of quarks and gluons at finite temperature and chemical potential using the hard thermal loop perturbation theory reorganization of finite temperature/density quantum chromodynamics. The computation utilizes a high temperature expansion through fourth order in the ratio of the chemical potential to temperature. This allows us to reliably access the region of high temperature and small chemical potential. We compare our final result for the leading-and next-to-leading-order hard thermal loop perturbation theory pressure at finite temperature and chemical potential with perturbative quantum chromodynamics calculations and available lattice quantum chromodynamics results.

We investigate fermion-antifermion production in $1+1$ dimensional QED using real-time lattice techniques. In this nonperturbative approach the full quantum dynamics of fermions is included, while the gauge field dynamics can be accurately represented by classical-statistical simulations for relevant field strengths. We compute the nonequilibrium time evolution of gauge-invariant correlation functions, implementing “low-cost” Wilson fermions. Introducing a lattice generalization of the Dirac-Heisenberg-Wigner function, we recover the Schwinger formula in $1+1$ dimensions in the limit of a static background field. We discuss the decay of the field due to the backreaction of the created fermion-antifermion pairs and apply the approach to strongly inhomogeneous gauge fields. The latter allows us to discuss the striking phenomenon of a linear rising potential building up between produced fermion bunches after the initial electric pulse ceased.

We study Bianchi cosmologies in the ghost-free bigravity theory, assuming both metrics to be homogeneous and anisotropic and of the Bianchi class A, which includes types I, II, ${\mathrm{VI}}_0$, ${\mathrm{VII}}_0$, VIII, and IX. We assume the Universe to contain a radiation and a nonrelativistic matter, with the cosmological term mimicked by the graviton mass. We find that, for generic initial values leading to a late-time self-acceleration, the Universe approaches a state with nonvanishing anisotropies. The anisotropy contribution to the total energy density decreases much slower than in General Relativity and shows the same falloff rate as the energy of a nonrelativistic matter. The solutions show a singularity in the past, and in the Bianchi IX case, the singularity is approached via a sequence of Kasner-like steps, which is characteristic of a chaotic behavior.

We present conservative $3+1$ general relativistic variable Eddington tensor radiation transport equations, including greater elaboration of the momentum space divergence (that is, the energy derivative term) than in previous work. These equations are intended for use in simulations involving numerical relativity, particularly in the absence of spherical symmetry. The independent variables are the lab frame coordinate basis spacetime position coordinates and the particle energy measured in the comoving frame. With an eye towards astrophysical applications—such as core-collapse supernovae and compact object mergers—in which the fluid includes nuclei and/or nuclear matter at finite temperature, and in which the transported particles are neutrinos, we pay special attention to the consistency of four-momentum and lepton number exchange between neutrinos and the fluid, showing the term-by-term cancellations that must occur for this consistency to be achieved.

On April 24, 2012, at 16:47:14 UT, the Gas Slit Camera (GSC) of the Japanese Monitor of All-sky X-ray Image (MAXI) instrument on the International Space Station detected a short x-ray transient lasting about 34 seconds. The MAXI/GSC transient was most likely a gamma-ray burst (GRB), because of the high Galactic latitude, spectral hardness ratio, and the absence of known bright x-ray sources at the detected position. In addition, the MAXI/GSC transient GRB 120424A coordinates were in the field of view of the inclined Tupi muon telescope located at ground level (3 m above sea level) at ($22.9°\mathrm{W}$, $43.2°\mathrm{S}$) in the South Atlantic Anomaly region. We report here that the Tupi telescope registered a muon excess with a signal significance $6.2\sigma$ within the MAXI/GSC transient time period. Assuming a power law function with a spectral index of $\gamma =-1.54$ in the tail of the primary gamma-ray energy spectrum, we can conclude that the fluence obtained from the muon excess detected by the Tupi telescope is consistent with the preliminary value obtained by the MAXI team. This result agrees with an assumption that the muons were produced in photonuclear reactions in the Earth’s atmosphere. In addition, we show also that the South Atlantic Anomaly region can be a favorable place at ground for the detection of the tail of the energy spectrum (the GeV counterpart) of some GRBs.

The growth rate of matter density perturbations has been measured from redshift-space distortion (RSD) in the galaxy power spectrum. We constrain the model parameter space for representative modified gravity models to explain the dark energy problem, by using the recent data of $f_m(z){\sigma }_8(z)$ at the redshifts $z=0.06–0.8$ measured by WiggleZ, SDSS LRG, BOSS, and 6dFGRS. We first test the Hu-Sawicki’s $f(R)$ dark energy model, and find that only the parameter region close to the standard $\Lambda$ cold dark matter model is allowed ($\lambda >12$ and 5 for $n=1.5$ and 2, respectively, at 95% C.L.). We then investigate the covariant Galileon model with a de Sitter attractor and show that the parameter space consistent with the background expansion history is excluded by the RSD data at more than $8\sigma$ because of the too large growth rate predicted by the theory. Finally, we consider the extended Galileon scenario, and we find that, in contrast to the covariant Galileon, there is a model parameter space for a tracker solution that is consistent with the RSD data within a $2\sigma$ level.

The potential between a heavy quark and an antiquark inside the quark-gluon plasma is studied on the basis of the gauge-gravity duality. A real-time complex potential $V_{Q\overline{Q}}(t,r)$ is derived from the Wilson loop, which is evaluated by its gravity dual in the Euclidean five-dimensional anti–de Sitter black hole metric. To make the analytic continuation from the imaginary time to the real time, specific variational configurations of the string world sheet in the Euclidean metric are introduced. A rapid approach of $V_{Q\overline{Q}}(t,r)$ to its stationary value is found at the time scale $t\simeq (\pi T{)}^{-1}$, and the imaginary part of $V_{Q\overline{Q}}(\infty ,r)$ becomes significant above the length scale $r=1.72(\pi T{)}^{-1}$. Also, these scales are independent of the ’t Hooft coupling $\lambda$. Implications of these results to the properties of heavy quarkonia in quark-gluon plasma are briefly discussed.

I suggest a practical particle model as an extension to the standard model. The model has a TeV scale $U(1{)}_{B-L}$ symmetry and it contains the fourth generation fermions with the TeV scale masses, including a cold dark matter neutrino. The model can completely account for the fermion flavor puzzles, the cold dark matter, and the matter-antimatter asymmetry through the leptogenesis. In particular, it is quite feasible and promising to test the model in future experiments.

We study the influence of the isospin asymmetry on the phase structure of strongly interacting quark matter near the critical point (CP) using a Ginzburg-Landau approach. The effect is found to be drastic, not only bringing about the shift of the location of the CP, but resulting in a rich phase structure in the vicinity of the CP. In particular, new tricritical and triple points emerge as soon as the isospin density becomes finite. Moreover, we find the CP being washed out from the phase diagram due to the stabilization of a homogeneous charged pion condensate when the isospin chemical potential exceeds a critical value. We derive a model-independent universal relation between the critical isospin chemical potential and the chiral condensate at the CP. We also study the effect of the $\mathrm{U}(1{)}_{\mathrm{A}}$ anomaly on the phase transition to the pion condensate in the vicinity of chiral crossover.

The very rare $B_d^0\to {\mu }^{+}{\mu }^{-}$ decay may be the last chance for new physics in the flavor sector at the LHC, before the 13 TeV run in 2015. Partially motivated by the known tension in $\sin 2\beta /{\varphi }_1$, enhancement beyond $(3–4)\times {10}^{-10}$ would likely imply the effect of a fourth generation of quarks. If observed at this level, the 126 GeV boson may not be the actual Higgs boson, while the $b\to d$ quadrangle (modulo $m_{t^{\prime }}$) would jump out. The 2011–2012 data is likely not sensitive to values below $3\times {10}^{-10}$, and the mode should continue to be pursued with the 13 TeV run.

Four-fermion operators have been used in the past to link the quark-exchange processes in the interaction of hadrons with the effective meson-exchange amplitudes. In this paper, we apply the similar idea of a Fierz rearrangement to the self-energy and electromagnetic processes and focus on the electromagnetic form factors of the nucleon and the electron. We explain the motivation of using four-fermion operators and discuss the advantage of this method in computing electromagnetic processes.

T2K has performed the first measurement of ${\nu }_{\mu }$ inclusive charged current interactions on carbon at neutrino energies of $\sim 1\mathrm{GeV}$ where the measurement is reported as a flux-averaged double differential cross section in muon momentum and angle. The flux is predicted by the beam Monte Carlo and external data, including the results from the NA61/SHINE experiment. The data used for this measurement were taken in 2010 and 2011, with a total of $10.8\times {10}^{19}$ protons-on-target. The analysis is performed on 4485 inclusive charged current interaction candidates selected in the most upstream fine-grained scintillator detector of the near detector. The flux-averaged total cross section is $⟨{\sigma }_{\mathrm{CC}}{⟩}_{\varphi }=(6.91\pm 0.13(\mathrm{stat})\pm 0.84(\mathrm{syst}))\times {10}^{-39}\frac{{\mathrm{cm}}^2}{\mathrm{nucleon}}$ for a mean neutrino energy of 0.85 GeV.

Poisson sigma models are a very rich class of two-dimensional theories that includes, in particular, all two-dimensional dilaton gravities. By using the Hamiltonian reduction method, we show that a Poisson sigma model (with a sufficiently well-behaving Poisson tensor) on a finite cylinder is equivalent to a noncommutative quantum mechanics for the boundary data.

We consider tidal encounters between a white dwarf and an intermediate mass black hole. Both weak encounters and those at the threshold of disruption are modeled. The numerical code combines mesh-based hydrodynamics, a spectral method solution of the self-gravity, and a general relativistic Fermi normal coordinate system that follows the star and debris. Fermi normal coordinates provide an expansion of the black hole tidal field that includes quadrupole and higher multipole moments and relativistic corrections. We compute the mass loss from the white dwarf that occurs in weak tidal encounters. Secondly, we compute carefully the energy deposition onto the star, examining the effects of nonradial and radial mode excitation, surface layer heating, mass loss, and relativistic orbital motion. We find evidence of a slight relativistic suppression in tidal energy transfer. Tidal energy deposition is compared to orbital energy loss due to gravitational bremsstrahlung, and the combined losses are used to estimate tidal capture orbits. Heating and partial mass stripping will lead to an expansion of the white dwarf, making it easier for the star to be tidally disrupted on the next passage. Finally, we examine angular momentum deposition. By including the octupole tide, we are able for the first time to calculate deflection of the center of mass of the star and debris. With this observed deflection, and taking into account orbital relativistic effects, we compute directly the change in orbital angular momentum and show its balance with computed spin angular momentum deposition.