We present a complete analysis of the imprint of tensor anisotropies on the Cosmic Microwave Background for a class of f(R) gravity theories within the PPF-CAMB framework. We derive the equations, both for the cosmological background and gravitationa
l wave perturbations, required to obtain the standard temperature and polarization power spectra, taking care to include all effects which arise from f(R) modifications of both the background and the perturbation equations. For R^n gravity, we show that for n different from 2, the initial conditions in the radiation dominated era are the same as those found in General Relativity. We also find that by doing simulations which involve either modifying the background evolution while keeping the perturbation equations fixed or fixing the background to be the Lambda-CDM model and modifying the perturbation equations, the dominant contribution to deviations from General Relativity in the temperature and polarization spectra can be attributed to modifications in the background. This demonstrates the importance of using the correct background in perturbative studies of f(R) gravity. Finally an enhancement in the B-modes power spectra is observed which may allow for lower inflationary energy scales.
A data-driven method was applied to measurements of Au+Au collisions at $sqrt{s_{_{rm NN}}} =$ 200 GeV made with the STAR detector at RHIC to isolate pseudorapidity distance $Deltaeta$-dependent and $Deltaeta$-independent correlations by using two- a
nd four-particle azimuthal cumulant measurements. We identified a component of the correlation that is $Deltaeta$-independent, which is likely dominated by anisotropic flow and flow fluctuations. It was also found to be independent of $eta$ within the measured range of pseudorapidity $|eta|<1$. The relative flow fluctuation was found to be $34% pm 2% (stat.) pm 3% (sys.)$ for particles of transverse momentum $p_{T}$ less than $2$ GeV/$c$. The $Deltaeta$-dependent part may be attributed to nonflow correlations, and is found to be $5% pm 2% (sys.)$ relative to the flow of the measured second harmonic cumulant at $|Deltaeta| > 0.7$.
Event-by-event fluctuations of the ratio of inclusive charged to photon multiplicities at forward rapidity in Au+Au collision at $sqrt{s_{NN}}$=200 GeV have been studied. Dominant contribution to such fluctuations is expected to come from correlated
production of charged and neutral pions. We search for evidences of dynamical fluctuations of different physical origins. Observables constructed out of moments of multiplicities are used as measures of fluctuations. Mixed events and model calculations are used as baselines. Results are compared to the dynamical net-charge fluctuations measured in the same acceptance. A non-zero statistically significant signal of dynamical fluctuations is observed in excess to the model prediction when charged particles and photons are measured in the same acceptance. We find that, unlike dynamical net-charge fluctuation, charge-neutral fluctuation is not dominated by correlation due to particle decay. Results are compared to the expectations based on the generic production mechanism of pions due to isospin symmetry, for which no significant (<1%) deviation is observed.
