In this work, we evaluate the contributions of the hadronic loops to the amplitudes of $J/\psi \to PV$ where $P$ and $V$ denote light pseudoscalar and vector mesons, respectively. By fitting data of two well measured channels of $J/\psi \to PV$, we obtain the contribution from the pure OZI process to the amplitude which is expressed by a phenomenological quantity $|{\mathcal{G}}_S^{PV}|$, and a parameter $\alpha$ existing in the calculations of the contribution of hadronic loops. In terms of $\alpha$ and $|{\mathcal{G}}_S^{PV}|$, we calculate the branching ratios of other channels and get results which are reasonably consistent with data. Our results show that the contributions from the hadronic loops are of the same order of magnitude as that from the OZI processes and the interference between the two contributions are destructive. The picture can be applied to study other channels such as PP or VV of decays of $J/\psi$.

The properties of jets produced in $p+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$ are measured using the method of two-particle correlations. The trigger particle is a leading particle from a large transverse momentum jet while the associated particle comes from either the same jet or the away-side jet. Analysis of the angular width of the near-side peak in the correlation function determines the jet-fragmentation transverse momentum $j_{\mathrm{T}}$. The extracted value, $\sqrt{⟨j_{\mathrm{T}}^2⟩}=585\pm 6(\mathrm{stat})\pm 15(\mathrm{sys})\mathrm{MeV}/c$, is constant with respect to the trigger particle transverse momentum, and comparable to the previous lower $\sqrt{s}$ measurements. The width of the away-side peak is shown to be a convolution of $j_{\mathrm{T}}$ with the fragmentation variable, $z$, and the partonic transverse momentum, $k_{\mathrm{T}}$. The $⟨z⟩$ is determined through a combined analysis of the measured ${\pi }^0$ inclusive and associated spectra using jet-fragmentation functions measured in $e^{+}{e}^{-}$ collisions. The final extracted values of $k_{\mathrm{T}}$ are then determined to also be independent of the trigger particle transverse momentum, over the range measured, with value of $\sqrt{⟨k_{\mathrm{T}}^2⟩}=2.68\pm 0.07(\mathrm{stat})\pm 0.34(\mathrm{sys})\mathrm{GeV}/c$.

In this work we consider the possibility of describing the current evolution of the universe, without the introduction of any cosmological constant or dark energy (DE), by modifying the Einstein-Hilbert (EH) action. In the context of the $f(R)$ gravities within the metric formalism, we show that it is possible to find an action without cosmological constant which exactly reproduces the behavior of the EH action with cosmological constant. In addition the $f(R)$ action is analytical at the origin having Minkowski and Schwarzschild solutions as vacuum solutions. The found $f(R)$ action is highly nontrivial and must be written in terms of hypergeometric functions but, in spite of looking somewhat artificial, it shows that the cosmological constant, or more generally the DE, is not a logical necessity.

We discuss the averaging problem in general relativity, using the form of the macroscopic gravity equations in the case of spherical symmetry in volume preserving coordinates. In particular, we calculate the form of the correlation tensor under some reasonable assumptions on the form for the inhomogeneous gravitational field and matter distribution. On cosmological scales, the correlation tensor in a Friedmann-Lemaître-Robertson-Walker (FLRW) background is found to be of the form of a spatial curvature. On astrophysical scales the correlation tensor can be interpreted as the sum of a spatial curvature and an anisotropic fluid. We briefly discuss the physical implications of these results.

In classical external gauge fields that fall off less fast than the inverse of the evolution parameter (time) of the system the implementability of a unitary perturbative scattering operator ($S$-matrix) is not guaranteed, although the field goes to zero. The importance of this point is exposed for the counterexample of low-dimensionally expanding systems. The issues of gauge invariance and of the interpretation of the evolution at intermediate times are also intricately linked to that point.

The factorization property of graviton scattering amplitudes is reviewed and shown to be valid only if the natural value of the gyromagnetic ratio $g_S=2$ is employed—independent of spin.

We present a new pseudospectral code for the simulation of evolution systems that are second order in space. We test this code by evolving a nonlinear scalar wave equation. These nonlinear waves can be stably evolved using very simple constant or radiative boundary conditions, which we show to be well-posed in the scalar wave case. The main motivation for this work, however, is to evolve black holes for the first time with the BSSN system by means of a spectral method. We use our new code to simulate the evolution of a single black hole using all applicable methods that are usually employed when the BSSN system is used together with finite differencing methods. In particular, we use black hole excision and test standard radiative and also constant outer boundary conditions. Furthermore, we study different gauge choices such as $1+\log $ and constant densitized lapse. We find that these methods in principle do work also with our spectral method. However, our simulations fail after about $100M$ due to unstable exponentially growing modes. The reason for this failure may be that we evolve the black hole on a full grid without imposing any symmetries. Such full grid instabilities have also been observed when finite differencing methods are used to evolve excised black holes with the BSSN system.

Applying the first and generalized second laws of thermodynamics for a realistic process of near critical black hole formation, we derive an entropy bound, which is identical to Bekenstein’s one for radiation. Relying upon this bound, we derive an absolute minimum mass $\sim 0.04\sqrt{g_{*}}{m}_{\mathrm{Pl}}$, where $g_{*}$ and $m_{\mathrm{Pl}}$ is the effective degrees of freedom for the initial temperature and the Planck mass, respectively. Since this minimum mass coincides with the lower bound on masses of which black holes can be regarded as classical against the Hawking evaporation, the thermodynamical argument will not prohibit the formation of the smallest classical black hole. For more general situations, we derive a minimum mass, which may depend on the initial value for entropy per particle. For primordial black holes, however, we show that this minimum mass can not be much greater than the Planck mass at any formation epoch of the Universe, as long as $g_{*}$ is within a reasonable range. We also derive a size-independent upper bound on the entropy density of a stiff fluid in terms of the energy density.

In light of the results from the WMAP three-year sky survey, we study an inflationary model based on a single-field polynomial potential, with up to quartic terms in the inflaton field. Our analysis is performed in the context of the Randall-Sundrum II braneworld theory, and we consider both the high-energy and low-energy (i.e. the standard cosmology case) limits of the theory. We examine the parameter space of the model, which leads to both large-field and small-field inflationary type solutions. We conclude that small-field inflation, for a potential with a negative mass square term, is in general favored by current bounds on the tensor-to-scalar perturbation ratio $r_s$.

We extend to higher order a recently published method for calculating the deflection angle of light in a general static and spherically symmetric metric. We have tested our method on the metric of Schwarzschild and Reissner-Nordström black holes, on the metric of a charged black hole coupled to Born-Infeld electrodynamics and on the metric of Weyl gravity. Since our method is geometrically convergent, as proved in our previous work, our analytical formulas obtained working to fourth order are sufficient to reach errors of few percents even in proximity of the photon sphere.

We present a method for constraining Lorentz violation in the electron sector, based on observations of the photons emitted by high-energy astrophysical sources. The most important Lorentz-violating operators at the relevant energies are parametrized by a tensor $c^{\nu \mu }$ with nine independent components. If $c$ is nonvanishing, then there may be either a maximum electron velocity less than the speed of light or a maximum energy for subluminal electrons; both these quantities will generally depend on the direction of an electron’s motion. From synchrotron radiation, we may infer a lower bound on the maximum velocity, and from inverse Compton emission, a lower bound on the maximum subluminal energy. With observational data for both these types of emission from multiple celestial sources, we may then place bounds on all nine of the coefficients that make up $c$. The most stringent bound, on a certain combination of the coefficients, is at the $6\times {10}^{-20}$ level, and bounds on the coefficients individually range from the $7\times {10}^{-15}$ level to the $2\times {10}^{-17}$ level. For most of the coefficients, these are the most precise bounds available, and with newly available data, we can already improve over previous bounds obtained by the same methods.

Pseudo-$C_{\ell }$ quadratic estimators for CMB temperature and polarization power spectra have been used in the analysis pipelines of many CMB experiments, such as WMAP and Boomerang. In the polarization case, these estimators mix E and B modes, in the sense that the estimated B-mode power is nonzero for a noiseless CMB realization which contains only E modes. Recently, Challinor, and Chon showed that for moderately sized surveys ($f_{\mathrm{sky}}\sim 0.01$), this mixing limits the gravity wave B-mode signal which can be detected using pseudo-$C_{\ell }$ estimators to $T/S\sim 0.05$. We modify the pseudo-$C_{\ell }$ construction, defining pure pseudo-$C_{\ell }$ estimators, which do not mix E and B modes in this sense. We study these estimators in detail for a survey geometry similar to that which has been proposed for the QUIET experiment, for a variety of noise levels, and both homogeneous and inhomogeneous noise. For noise levels $\lesssim 20\mu \mathrm{K}\mathrm{\text{−}}\mathrm{arc}\min$, our modification significantly improves the B-mode power spectrum errors obtained using pseudo-$C_{\ell }$ estimators. In the homogeneous case, we compute optimal power spectrum errors using a Fisher matrix approach, and show that our pure pseudo-$C_{\ell }$ estimators are roughly 80% of optimal, across a wide range of noise levels. There is no limit, imposed by the estimators alone, to the value of $T/S$ which can be detected.

We compare three methods for computing invariant Lyapunov exponents (LEs) in general relativity. These methods involve the geodesic deviation vector technique (M1), the two-nearby-orbits method with projection operations and with coordinate time as the independant variable (M2), and the two-nearby-orbits method without projection operations and with proper time as the independent variable (M3). An analysis indicates that M1 and M3 do not need any projection operation. In general, the values of LEs from the three methods are almost the same. However, M2 fails for some specific cases. As a result, M3 is the most preferable to calculate LEs in most cases. In addition, we propose to construct the invariant fast Lyapunov indictor (FLI) with two-nearby-trajectories and give its algorithm in order to quickly distinguish chaos from order. Taking a static axisymmetric spacetime as a physical model, we apply different algorithms of the FLI to explore the global dynamics of phase space of the system where regions of chaos and order are clearly identified.

A precision measurement of the gravitational constant $G$ has been made using a beam balance. Special attention has been given to determining the calibration, the effect of a possible nonlinearity of the balance and the zero-point variation of the balance. The equipment, the measurements, and the analysis are described in detail. The value obtained for $G$ is $6.674252(109)(54)\times {10}^{-11}{\mathrm{m}}^3{\mathrm{kg}}^{-1}{\mathrm{s}}^{-2}$. The relative statistical and systematic uncertainties of this result are $16.3\times {10}^{-6}$ and $8.1\times {10}^{-6}$, respectively.

We present new results from our test of Lorentz invariance, which compares two orthogonal cryogenic sapphire microwave oscillators rotating in the lab. We have now acquired over 1 year of data, allowing us to avoid the short data set approximation (less than 1 year) that assumes no cancellation occurs between the ${\tilde{\kappa }}_{e-}$ and ${\tilde{\kappa }}_{o+}$ parameters from the photon sector of the standard model extension. Thus, we are able to place independent limits on all eight ${\tilde{\kappa }}_{e-}$ and ${\tilde{\kappa }}_{o+}$ parameters. Our result represents up to a factor of 10 improvement over previous nonrotating measurements (which independently constrained seven parameters) and is a slight improvement (except for ${\tilde{\kappa }}_{e-}^{ZZ}$) over results from previous rotating experiments that assumed the short data set approximation. Also, an analysis in the Robertson-Mansouri-Sexl framework allows us to place a new limit on the isotropy parameter $P_{MM}=\delta -\beta +\frac{1}{2}$ of $9.4(8.1)\times {10}^{-11}$, an improvement of a factor of 2.

In the framework of perturbative QCD and nonrelativistic bound state formalism, we calculate the production of ${\rm Y}$ mesons associated with open-beauty particles at the Tevatron and LHC conditions. We show that the contribution from the ${\rm Y}+b+\overline{b}$ channel becomes comparable with that of ${\rm Y}$ sole production at the LHC at high enough transverse momenta, but is small at the Tevatron. We investigate the ${\rm Y}$ polarization effects and kinematic correlations between ${\rm Y}$ mesons and the accompanying open-beauty mesons. We show that the correlations are sensitive to the initial $k_t$ of the colliding partons, and so, can be considered as an additional test discriminating the collinear parton model and the $k_t$-factorization approach.

We consider the minimal coupling of two photons to neutral scalar and pseudoscalar fields, as, for instance, in the case of the Higgs boson and axion, respectively. In this framework, we analyze the photon dispersion relations in the presence of static and homogeneous external magnetic and electric fields, by taking into account the contribution of the imaginary part of the scalar/pseudoscalar self-energy. We show that this contribution cannot be neglected when it is of the same order as the photon-scalar/pseudoscalar mixing term. In addition to the usual lightlike photon propagation mode, with a refraction index $n>1$, a massive mode with mass of the order of the coupled boson mass can be induced, provided that the external field is above a particular critical value. Depending on the values of the external field, photon energy, and mass of the scalar/pseudoscalar particle, the scalar/pseudoscalar width could induce a sizable rate of photon splitting in two photons due to a strong resonant phenomenon. This effect has no practical laboratory applications for the Higgs physics due to the very large critical external magnetic or electric fields involved, for a photon energy of the order of a TeV. However, it can have relevant consequences in the axion physics or in any other scenario where light neutral scalar/pseudoscalar fields have minimal coupling with two photons.

Radiative decays of the $\psi (2S)$ into $\gamma K\overline{K}\pi$ and $\gamma \eta {\pi }^{+}{\pi }^{-}$ final states are studied using $14\times {10}^6$ $\psi (2S)$ events collected with the BESII detector. Branching fractions or upper limits on the branching fractions of $\psi (2S)$ and ${\chi }_{cJ}$ decays are reported. No significant signal for $\eta (1405)/\eta (1475)$ is observed in the $K\overline{K}\pi$ or $\eta {\pi }^{+}{\pi }^{-}$ mass spectra, and upper limits on the branching fractions of $\psi (2S)\to \gamma \eta (1405)/\eta (1475)$, $\eta (1405)/\eta (1475)\to K\overline{K}\pi$, and $\eta {\pi }^{+}{\pi }^{-}$ are determined.