123125789
THE INFLUENCE OF DARK ENERGY ON THE LARGE SCALE STRUCTURE FORMATION
Inhomogeneity at small scales (Mpcs) of our universe is manifest from observations. In regions smaller than 8h-1 Mpc galaxies tend to cluster instead of showing a Poisson distribution. The properties of the spherical collapse model which approximately depicts this nonlinearity of the density perturbation are investigated when there exits dark energy. The evolution of a spherical perturbation depends only on the initial critical overdensity threshold for the collapse, δc and its value approaches to 1.58 instead of the conventionally known 1.69 independent of the value of the equation of state of dark energy.
118471394
Palatini f(R) Cosmology
We investigate the modified gravity theories in terms of the effective dark energy models. We compare the cosmic expansion history and the linear growth in different models. We also study the evolution of linear cosmological perturbations in modified theories of gravity assuming the Palatini formalism. We find the stability of the superhorizon metric evolution depends on models. We also study the matter density fluctuation in the general gauge and show the differential equations in super and sub-horizon scales.
3165699
Growth index in an accelerating universe
We obtain the exact analytic form of growth index ($f = \Omega_{m}(a)^{\gamma}$) at present epoch in a flat universe for the general value of constant equation of state of dark energy $\omega_{de}$. For the cosmological constant ($\omega_{de} = -1$) we obtain $\gamma = 0.5547$ which is very close to the well known value 6/11. However, if $\omega_{de} = -0.9$, then $\gamma$ gives rise to 0.6405. This result is quite different from that of some other literatures. This discrepancy happens because the numerical solution includes not only the growing mode solution but also the decaying one in some literatures. Thus, the numerical estimation of $\delta$ is over estimated in some references. $\Omega_{m}^{0}$ dependence of $\gamma$ is fairly small for the viable range of the current matter energy density $0.2 \leq \Omega_{m}^{0} \leq 0.3$. (0.6% and 3% changes in $\gamma$ for $\omega_{de}$ equal to -1 and -0.9, respectively.) The difference of peculiar velocity values from the different choices of $\gamma$ is about 11% for $\Omega_{m}^{0} = 0.3$. This simple but accurate formula which covers a large class of dark energy models will provide a practical tool for galaxy redshift survey to measure the matter density and the peculiar velocity.
116349147
Cluster number counts in quintessence models
Abstract Even though the abundance and evolution of clusters have been used to study the cosmologicalparameters includingthe propertiesof darkenergy owing to their puredependenceon the geometryof the Universe and the power spectrum, it is necessary to pay particular attention to the eﬀectsof dark energy on the analysis. We obtain the explicit dark energy dependent rms linear massﬂuctuation σ 8 which is consistent with the CMB normalization with less than 2 % errors for generalconstant dark energy equation of state, ω Q . Thus, we do not have any degeneracy between σ 8 and the matter energy density contrast Ω 0m . When we use the correct value of the critical densitythreshold δ c = 1.58 obtained recently [30, 31] into the cluster number density n calculation in thePress-Schechter (PS) formalism, n increases as compared to the one obtained by using δ c = 1.69by about 60, 80, and 110 % at z = 0, 0.5, and 1, respectively. Thus, PS formalism predictsthe cluster number consistent with both simulation and observed data at the high mass region.We also introduce the improved coeﬃcients of Sheth-Tormen (ST) formalism, which is consistentwith the recently suggested mass function [36]. We found that changing ω
15011888
Effect on cosmic microwave background polarization of coupling of quintessence to pseudoscalar formed from the electromagnetic field and its dual.
We present the full set of power spectra of cosmic microwave background (CMB) temperature and polarization anisotropies due to the coupling between quintessence and pseudoscalar of electromagnetism. This coupling induces a rotation of the polarization plane of the CMB, thus resulting in a nonvanishing B mode and parity-violating TB and EB modes. Using the BOOMERANG data from the flight of 2003, we derive the most stringent constraint on the coupling strength. We find that in some cases the rotation-induced B mode can confuse the hunting for the gravitational lensing-induced B mode.
1970563
Can strong gravitational lensing constrain dark energy
We discuss the ratio of the angular diameter distances from the source to the lens, D{sub ds}, and to the observer at present, D{sub s}, for various dark energy models. It is well known that the difference of D{sub s}s between the models is apparent and this quantity is used for the analysis of Type Ia supernovae. However we investigate the difference between the ratio of the angular diameter distances for a cosmological constant, (D{sub ds}/D{sub s}){sup {lambda}}, and that for other dark energy models, (D{sub ds}/D{sub s}){sup other}, in this paper. It has been known that there is lens model degeneracy in using strong gravitational lensing. Thus, we investigate the model independent observable quantity, Einstein radius ({theta}{sub E}), which is proportional to both D{sub ds}/D{sub s} and velocity dispersion squared, {sigma}{sub v}{sup 2}. D{sub ds}/D{sub s} values depend on the parameters of each dark energy model individually. However, (D{sub ds}/D{sub s}){sup {lambda}}-(D{sub ds}/D{sub s}){sup other} for the various dark energy models, is well within the error of {sigma}{sub v} for most of the parameter spaces of the dark energy models. Thus, a single strong gravitational lensing by use of the Einstein radius may not be a proper method tomore » investigate the property of dark energy. However, better understanding to the mass profile of clusters in the future or other methods related to arc statistics rather than the distances may be used for constraints on dark energy.« less
116942523
Microwave instability near transition energy
Monte Carlo simulation for the microwave instability agrees with analytic calculation solving the Vlasov equation, provided that bunch shape distortion due to coupling is taken into account. 9 refs., 2 figs.
17587151
Nuclear Density-Dependent Effective Coupling Constants in the Mean-Field Theory
It is shown that the equation of state of nuclear matter can be determined within the mean-field theory of $\sigma \omega$ model provided only that the nucleon effective mass curve is given. We use a family of the possible nucleon effective mass curves that reproduce the empirical saturation point in the calculation of the nuclear binding energy curves in order to obtain density-dependent effective coupling constants. The resulting density-dependent coupling constants may be used to study a possible equation of state of nuclear system at high density or neutron matter. Within the constraints used in this paper to $M^*$ of nuclear matter at saturation point and zero density, neutron matter of large incompressibility is strongly bound at high density while soft neutron matter is weakly bound at low density. The study also exhibits the importance of surface vibration modes in the study of nuclear equation of state.
12450781
Topological Chern-Simons sigma model
We consider topological twisting of recently constructed Chern-Simons-matter theories in three dimensions with = 4 or higher supersymmetry. We enumerate physically inequivalent twistings for each , and find two different twistings for = 4, one for = 5,6, and four for = 8. We construct the two types of = 4 topological theories, which we call A/B-models, in full detail. The A-model has been recently studied by Kapustin and Saulina. The B-model is new and it consists solely of a Chern-Simons term of a complex gauge field up to BRST-exact terms. We also compare the new theories with topological Yang-Mills theories and find some interesting connections. In particular, the A-model seems to offer a new perspective on Casson invariant and its relation to Rozansky-Witten theory.
91854570
Effects of chiral symmetry restoration in nuclear medium
118407545
TASI Lectures on Emergence of Supersymmetry, Gauge Theory and String in Condensed Matter Systems
The lecture note consists of four parts. In the first part, we review a 2+1 dimensional lattice model which realizes emergent supersymmetry at a quantum critical point. The second part is devoted to a phenomenon called fractionalization where gauge boson and fractionalized particles emerge as low energy excitations as a result of strong interactions between gauge neutral particles. In the third part, we discuss about stability and low energy effective theory of a critical spin liquid state where stringy excitations emerge in a large N limit. In the last part, we discuss about an attempt to come up with a prescription to derive holographic theory for general quantum field theory.