It is well known that Minkowski vacuum appears as a thermal bath in the Rindler spacetime when the modes on the left wedge are traced out. We introduce the concept of a Rindler-Rindler spacetime, obtained by a further coordinate transformation from the Rindler spacetime, in a manner similar to the transformation from inertial to Rindler frame. We show that the Rindler vacuum appears as a thermal state in the Rindler-Rindler frame. Further, the spectrum of particles seen by the Rindler-Rindler observers in the original Minkowski vacuum state is shown to be identical to that seen by a detector accelerating through a real thermal bath. Thus the Davies-Unruh effect acts as a proxy for a real thermal bath, for a certain class of observers in the Rindler-Rindler spacetime. We interpret this similarity as indicating further evidence of the indistinguishability between thermal and quantum fluctuations along the lines of the recent work in Kolekar and Padmanabhan [arXiv:1308.6289]. The implications are briefly discussed.

Quadratic curvature gravity equations are projected to a complex null coframe by using the algebra of exterior forms and expressed in terms of the spinor quantities defined originally by Newman and Penrose. As an application, a new family of impulsive gravitational wave solutions propagating in various Petrov type D backgrounds is introduced.

We consider two different definitions for loop corrections to the primordial power spectra. One of these is to simply correct the mode functions in the tree order relations using the linearized effective field equations. The second definition involves the spatial Fourier transform of the two-point correlator. Although the two definitions agree at tree order, we show that they disagree at one loop using the Schwinger-Keldysh formalism, so there are at least two plausible ways of loop correcting the tree order result. We discuss the advantages and disadvantages of each.

We study the $B-L$ gauge extension of the Standard Model which contains a singlet scalar and three right-handed neutrinos. The vacuum expectation value of the singlet scalar breaks the $U(1{)}_{B-L}$ symmetry. Here the third-generation right-handed neutrino is qualified as the dark matter candidate, as an artifact of $Z_2$-charge assignment. Relic abundance of the dark matter is consistent with WMAP9 and PLANCK data, only near scalar resonances where dark matter mass is almost half of the scalar boson masses. Requiring correct relic abundance, we restrict the parameter space of the scalar mixing angle and mass of the heavy scalar boson of this model. Besides this, the maximum value of the spin-independent scattering cross section off nucleon is well below the Xenon100 and recent LUX exclusion limits and can be probed by future Xenon1T experiments. In addition, we compute the annihilation of the dark matter into a two-photon final state in detail and compare with the Fermi-LAT upper bound on $⟨\sigma v{⟩}_{\gamma \gamma }$ for the NFW and Einasto profile.

Varying gravitational constant $G(t)$ (VG) cosmology is studied in this paper, where the modified Friedmann equation and the modified energy conservation equation are given with respect to the constant-$G$ theory. Considering the extended Chaplygin gas (ECG) as background fluid (or thinking that ECG fluid is induced by the variation of $G$), the unified model of dark matter and dark energy is obtained in VG theory. The parameter spaces are investigated in the VG-ECG model by using the recent cosmic data. Constraint results show $\beta =-\frac{\stackrel{.}{G}}{HG}=-0.003_{-0.020-0.055}^{+0.021+0.034}$ for the VG-GCG unified model and $\beta =-0.027_{-0.032-0.066}^{+0.032+0.059}$ for the VG-MCG unified model. Equivalently, they correspond to the limits on the current variation of Newton’s gravitational constant at 95.4% confidence level $|\frac{\stackrel{.}{G}}{G}{|}_{\text{today}}\lesssim 4.1\times 10^{-12}{\mathrm{yr}}^{-1}$ and $|\frac{\stackrel{.}{G}}{G}{|}_{\text{today}}\lesssim 6.6\times 10^{-12}{\mathrm{yr}}^{-1}$. And for $z\le 3.5$, bounds on the variation of $\frac{\stackrel{.}{G}}{G}$ in the VG-ECG unified model are in accordance with the experiment explorations of varying $G$. In addition, in VG theory the used observational data point still cannot distinguish the VG-GCG and VG-MCG unified model from the most popular $\mathrm{\Lambda }\mathrm{CDM}$ cosmology. Furthermore, to see the effects of varying $G$ and physical properties for VG-ECG fluid, we discuss the evolutionary behaviors of cosmological quantities in VG theory, such as $\frac{\stackrel{.}{G}}{G}$, $\frac{\stackrel{..}{G}}{G}$ and equation of state $w$, etc. For $\beta <0$ a quintom scenario crossing over $w=-1$ can be realized in the VG-GCG model.

Our observations of the Universe are fundamentally anisotropic, with data from galaxies separated transverse to the line of sight coming from the same epoch while those from galaxies separated parallel to the line of sight come from different times. Moreover, galaxy peculiar velocities along the line of sight change their redshift, giving redshift space distortions. We perform a full two-dimensional anisotropy analysis of galaxy clustering data from the 264,283 galaxies in the BOSS DR9 CMASS at $z\sim 0.43–0.7$, fitting in a substantially model-independent manner the angular diameter distance $D_A$, Hubble parameter $H$, and growth rate $d\delta /d\ln a$ without assuming a dark energy model. The results demonstrate consistency with LCDM expansion and growth, hence also testing general relativity. We also point out the interpretation dependence of the effective redshift $z_{\text{eff}}$, and its cosmological impact for next generation surveys.

According to a generalization of black hole thermodynamics to a cosmological framework, it is possible to define a temperature for the cosmological horizon. The hypothesis of thermal equilibrium between the dark energy and the horizon has been considered by many authors. We find the restrictions imposed by this hypothesis on the energy transfer rate ($Q_i$) between the cosmological fluids, assuming that the temperature of the horizon has the form $T=b/2\pi R$, where $R$ is the radius of the horizon. We more specifically consider two types of dark energy: Chaplygin gas (CG) and dark energy with a constant equation of state parameter ($w\mathrm{DE}$). In each case, we show that for a given radius $R$, there is a unique term $Q_{\mathrm{de}}$ that is consistent with thermal equilibrium. We also consider the situation where, in addition to dark energy, other fluids (cold matter, radiation) are in thermal equilibrium with the horizon. We find that the interaction terms required for this will generally violate energy conservation ($\sum _i{Q}_i=0$).

Cosmic microwave background (CMB) polarimeters aspire to measure the faint $B$-mode signature predicted to arise from inflationary gravitational waves. They also have the potential to constrain cosmic birefringence, rotation of the polarization of the CMB arising from parity-violating physics, which would produce nonzero expectation values for the CMB’s temperature to $B$-mode correlation ($TB$) and $E$-mode to $B$-mode correlation ($EB$) spectra. However, instrumental systematic effects can also cause these $TB$ and $EB$ correlations to be nonzero. In particular, an overall miscalibration of the polarization orientation of the detectors produces $TB$ and $EB$ spectra which are degenerate with isotropic cosmological birefringence, while also introducing a small but predictable bias on the $BB$ spectrum. We find that Bicep1 three-year spectra, which use our standard calibration of detector polarization angles from a dielectric sheet, are consistent with a polarization rotation of $\alpha =-2.77°\pm 0.86°\text{(statistical)}\pm 1.3°\text{(systematic)}$. We have revised the estimate of systematic error on the polarization rotation angle from the two-year analysis by comparing multiple calibration methods. We also account for the (negligible) impact of measured beam systematic effects. We investigate the polarization rotation for the Bicep1 100 GHz and 150 GHz bands separately to investigate theoretical models that produce frequency-dependent cosmic birefringence. We find no evidence in the data supporting either of these models or Faraday rotation of the CMB polarization by the Milky Way galaxy’s magnetic field. If we assume that there is no cosmic birefringence, we can use the $TB$ and $EB$ spectra to calibrate detector polarization orientations, thus reducing bias of the cosmological $B$-mode spectrum from leaked $E$-modes due to possible polarization orientation miscalibration. After applying this “self-calibration” process, we find that the upper limit on the tensor-to-scalar ratio decreases slightly, from $r<0.70$ to $r<0.65$ at 95% confidence.

Optical rigidity in the Advanced LIGO gravitational-wave detector, operated on the dark port regime, is unstable. We show that the same interferometer with excluded symmetric mechanical mode but with unbalanced arms allows us to get stable optical spring for the antisymmetric mechanical mode. The arm detuning necessary to get stability is shown to be a small one—it corresponds to small power in the signal port. We show that stable optical spring may be also obtained in the Michelson-Sagnac interferometer with both power and signal recycling mirrors and unbalanced arms.

Proposals were made earlier in 2008 to use atom interferometry based on Raman transitions for gravitational wave observations in space. Recently, Graham et al. have suggested a new atom interferometry method for such observations based on laser-induced single-photon transitions on highly forbidden optical transitions such as those used in recently developed optical clocks. However, a number of additional requirements that are not discussed by Graham et al. have to be considered if the sensitivity level they suggest is to be reached. When all of the requirements are considered, it appears that such an atom interferometry mission would be much more complex than a laser interferometry mission with better overall sensitivity.

KAGRA, the Japanese interferometric gravitational wave detector currently under construction, will employ sapphire test masses for its cryogenic operation. Sapphire has an advantage in its higher thermal conductivity near the operating temperature 20 K compared to fused silica used in other gravitational wave detectors, but there are some uncertain properties for the application such as hardness, optical absorption, and birefringence. We introduce an optical design of the test masses and our recent R&D results to address the above properties. Test polish of sapphire substrate has especially proven that specifications on the surface are sufficiently met. Recent measurements of absorption and inhomogeneity of the refractive index of the sapphire substrate indicate that the other properties are also acceptable to use sapphire crystal as test masses.

In supersymmetric models, very heavy stop squarks introduce large logarithms into the computation of the Higgs boson mass. Although it has long been known that in simple cases these logs can be resummed using effective field theory techniques, it is technically easier to use fixed-order formulas, and many public codes implement the latter. We calculate three- and four-loop next-to-next-to-leading-log corrections to the Higgs mass and compare the fixed-order formulas numerically to the resummation results in order to estimate the range of supersymmetry scales where the fixed-order results are reliable. We find that the four-loop result may be accurate up to a few tens of TeV. We confirm an accidental cancellation between different three-loop terms, first observed in S. P. Martin, Phys. Rev. D 75, 055005 (2007), and show that it persists to higher scales and becomes more effective with the inclusion of higher radiative corrections. Existing partial three-loop calculations that include only one of the two cancelling terms may overestimate the Higgs mass. We give analytic expressions for the three- and four-loop corrections in terms of Standard Model parameters and provide a complete dictionary for translating parameters between the SM and the MSSM and the $\overline{\mathrm{MS}}$ and $\overline{\mathrm{DR}}$ renormalization schemes.

A variety of new physics models predict the existence of extra charged gauge bosons ($W^{\prime }$). It is verified that $W^{\prime }$ and top quark associated production is a promising process to search for the $W^{\prime }$ signal at the LHC. We study the collider signatures of $\text{multijets}+\text{lepton}+{\cancel{E}}_T$ by reconstructing the $t{W}^{\prime }$ intermediate state through the decay modes of $W^{\prime }\to tb$, $W^{\prime }\to q{\overline{q}}^{\prime }$, and $W^{\prime }\to l\nu$, respectively. An angular distribution related to charged lepton and top quark moving direction is provided to distinguish alternative left-handed or right-handed chiral couplings of $W^{\prime }$ to quarks in the hadronic decay modes. The superiority on the search of $W^{\prime }$ is demonstrated in the leptonic decay channel for the left-handed type interaction, which is forbidden for the right-handed type interaction in the most theories. To be more realistic, the relevant standard model backgrounds are simulated. We adopt various kinematic cuts to suppress the backgrounds and collect the integral luminosity needed for the corresponding process detected at the LHC with $3\sigma$ sensitivity. We also provide a forward-backward asymmetry which is related to the chirality of $W^{\prime }$. The successive studies can shed light on the potential searching for the $W^{\prime }$ signal as well as distinguishing typical new physics models.

Two-color lattice QCD with $N_f=4$ staggered fermion degrees of freedom (no rooting trick is applied) with equal electric charge $q$ is studied in a homogeneous magnetic background field $B$ and at nonzero temperature $T$. In order to circumvent renormalization as a function of the bare coupling, we apply a fixed-scale approach. We study the influence of the magnetic field on the critical temperature. At rather small pseudoscalar meson mass [$m_{\pi }\approx 175\mathrm{MeV}\approx T_c(B=0)$] we confirm a monotonic rise of the quark condensate $⟨\overline{\psi }\psi ⟩$ with increasing magnetic field strength, i.e., magnetic catalysis, as long as one is staying within the confinement or deconfinement phase. In the transition region we find indications for a nonmonotonic behavior of $T_c(B)$ at low magnetic field strength ($qB<0.8{\mathrm{GeV}}^2$) and a clear rise at stronger magnetic field. The conjectured existence of a minimum value $T_c(B^{*})<T_c(B=0)$ would leave a temperature window for a decrease of $⟨\overline{\psi }\psi ⟩$ with rising $B$ (inverse magnetic catalysis) also in the present model.

We study the production of two almost back-to-back hadrons from the annihilation of an electron and a positron, allowing for the polarization of all particles involved. In particular, we conduct a general (model-independent) structure function decomposition of the cross section for the case $e^{+}{e}^{-}\to {\gamma }^{*}\to h_a{h}_{b}X$. Moreover, using the parton model we calculate the relevant structure functions in terms of twist-2 transverse momentum dependent (TMD) fragmentation functions (FFs). We also give results for the situation $e^{+}{e}^{-}\to Z^{*}\to h_a{h}_{b}X$ (including $\gamma \text{−}Z$ interference) within this model. This is the first time a complete framework has been presented for the examination of TMD FFs within $e^{+}{e}^{-}\to h_a{h}_{b}X$. We also specify certain parts of our analysis that hold for the triple-polarized semi-inclusive deep-inelastic scattering process and for di-hadron fragmentation. Furthermore, we give an explicit prescription of how our work can be translated to the Drell-Yan reaction, which provides, for the first time, full results for double-polarized Drell-Yan that include electroweak effects. We further discuss the relevance of our $e^{+}{e}^{-}\to h_a{h}_{b}X$ results for future experiments at $e^{+}{e}^{-}$ machines.

We study the pion distribution amplitude ($\pi \mathrm{DA}$) in the context of a nonlocal chiral quark model. The corresponding Lagrangian reproduces the phenomenological values of the pion mass and decay constant, as well as the momentum dependence of the quark propagator obtained in lattice calculations. It is found that the obtained $\pi \mathrm{DA}$ has two symmetric maxima, which arise from the new contributions generated by the nonlocal character of the interactions. This $\pi \mathrm{DA}$ is applied to leading order and next-to-leading order calculations of the pion-photon transition form factor. Implications of the results are discussed.

We study the reaction $e^{+}{e}^{-}\to \overline{D}D$ near threshold in the ${{}^{3}P}_0$ nonrelativistic quark model, including as intermediate states the $J/\psi$, $\psi (2S)$, $\psi (3770)$, and $\psi (4040)$ mesons. The work reveals that experimental data strongly favor one of the two $\psi (2S)-\psi (3770)$ mixing angles derived by fitting to the $e^{-}{e}^{+}$ partial decay widths of the $\psi (2S)$ and $\psi (3770)$ mesons. The meson $X(3940)$ as well as the resonance around 3.9 GeV observed by the Belle and BABAR Collaborations in the reaction $e^{+}{e}^{-}\to \overline{D}D$ is unlikely to be a $c\overline{c}\hspace{0.17em}{I}^G(J^{PC})=0^{-}(1^{--})$ state.

We provide a general argument for the possible existence of a new critical point associated with a deconfinement phase transition in QCD at finite temperature $T$ and in a magnetic field $B$ with zero chemical potential. This is the first example of a QCD critical point in a physical external parameter region that can be studied using lattice QCD simulations without suffering from a sign problem.

The role of the axial anomaly in the chiral phase transition at finite temperature and quark chemical potential is investigated within a nonperturbative functional renormalization group approach. The flow equation for the grand potential is solved to leading order in a derivative expansion of a three-flavor quark-meson model truncation. The results are compared with a standard and an extended mean-field analysis, which facilitates the exploration of the influence of bosonic and fermionic fluctuations, respectively, on the phase transition. The influence of $U(1{)}_A$-symmetry breaking on the chiral transition, the location of a possible critical end point in the phase diagram and the quark mass sensitivity are studied in detail.

A measurement of the cross section for the production of isolated prompt photons in $pp$ collisions at a center-of-mass energy $\sqrt{s}=7\mathrm{TeV}$ is presented. The results are based on an integrated luminosity of $4.6{\mathrm{fb}}^{-1}$ collected with the ATLAS detector at the LHC. The cross section is measured as a function of photon pseudorapidity ${\eta }^{\gamma }$ and transverse energy $E_{\mathrm{T}}^{\gamma }$ in the kinematic range $100\le E_{\mathrm{T}}^{\gamma }<1000\mathrm{GeV}$ and in the regions $|{\eta }^{\gamma }|<1.37$ and $1.52\le |{\eta }^{\gamma }|<2.37$. The results are compared to leading-order parton-shower Monte Carlo models and next-to-leading-order perturbative QCD calculations. Next-to-leading-order perturbative QCD calculations agree well with the measured cross sections as a function of $E_{\mathrm{T}}^{\gamma }$ and ${\eta }^{\gamma }$.