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.
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.
54971266
Effects on the two-point correlation function from the coupling of quintessence to dark matter
We investigate the effects of the nonminimal coupling between the scalar field dark energy (quintessence) and the dark matter on the two-point correlation function. It is well known that this coupling shifts the turnover scale as well as suppresses the amplitude of the matter power spectrum. However, these effects are too small to be observed when we limit the coupling strength to be consistent with observations. Since the coupling of quintessence to baryons is strongly constrained, species-dependent coupling may arise. This results in a baryon bias that is different from unity. Thus, we investigate the correlation function in this coupled model. We are able to observe the enhancement of the baryon acoustic oscillation (BAO) peak due to the increasing bias factor of baryon from this species-dependent coupling. In order to avoid the damping effect of the BAO signature in the matter power spectrum due to nonlinear clustering, we consider the coupling effect on the BAO bump in the linear regime. This provides an alternative method to constrain the coupling of dark energy to dark matter.
118495217
Evidence for departure from \Lambda CDM with LSS
We investigate the growth index parameter \gamma and the time variation of the gravitational constant G_{eff} by using the currently available growth function f(z) data at different redshifts, with and without scaling to the fiducial \Lambda CDM model. We inquire the four different models of \gamma including a constant \gamma. From a \chi^2 minimization, we constrain the parameter spaces of models and show that \Lambda CDM model is excluded by 1-\sigma level from current f(z) data. G_{eff} is different from the Newton's gravitational constant G_{N} in modified gravity theories and interestingly, the current data shows that G_{eff} \neq G_{N} at z \gtrsim 0.2 \sim 0.3 at 3-\sigma level. From these, we conclude that Einstein's General Relativity with \Lambda CDM is ruled out by 99% confidence level from large scale structure observations.
53130301
Exact third-order density perturbation and one-loop power spectrum in general dark energy models
Abstract Under the standard perturbation theory (SPT), we obtain the fully consistent third-order density fluctuation and kernels for the general dark energy models without using the Einstein–de Sitter (EdS) universe assumption for the first time. We also show that even though the temporal and spatial components of the SPT solutions cannot be separable, one can find the exact solutions to any order in general dark energy models. With these exact solutions, we obtain the less than % error correction of one-loop matter power spectrum compared to that obtained from the EdS assumption for k = 0.1 h Mpc − 1 mode at z = 0 ( 1 , 1.5 ) . Thus, the EdS assumption works very well at this scale. However, if one considers the correction for P 13 , the error is about 6 (9, 11)% for the same mode at z = 0 ( 1 , 1.5 ) . One absorbs P 13 into the linear power spectrum in the renormalized perturbation theory (RPT) and thus one should use the exact solution instead of the approximation one. The error on the resummed propagator N of RPT is about 14 (8, 6)% at z = 0 ( 1 , 1.5 ) for k = 0.4 h Mpc − 1 . For k = 1 h Mpc − 1 , the error correction of the total matter power spectrum is about 3.6 (4.6, 4.5)% at z = 0 ( 1 , 1.5 ) . Upcoming observation is required to archive the sub-percent accuracy to provide the strong constraint on the dark energy and this consistent solution is prerequisite for the model comparison.
119104224
A study of Wall-Crossing: flavored kinks in D = 2 QED
We study spectrum of D = 2 $$\mathcal {N} $$ = (2, 2) QED with N + 1 massive charged chiral multiplets, with care given to precise supermultiplet countings. In the infrared the theory flows to ℂℙN model with twisted masses, where we construct generic flavored kink solitons for the large mass regime, and study their quantum degeneracies. These kinks are qualitatively different and far more numerous than those of small mass regime, with features reminiscent of multi-pronged (p, q) string web, complete with the wall-crossing behavior. It has been also conjectured that spectrum of this theory is equivalent to the hypermultiplet spectrum of a certain D = 4 Seiberg-Witten theory. We find that the correspondence actually extends beyond hypermultiplets in D = 4, and that many of the relevant indices match. However, a D = 2 BPS state is typically mapped to several different kind of dyons whose individual supermultiplets are rather complicated; the match of index comes about only after summing over indices of these different dyons. We note general wall-crossing behavior of flavored BPS kink states, and compare it to those of D = 4 dyons.
37603515
Light Gravitinos at Colliders and Implications for Cosmology
Light gravitinos, with mass in the eV to MeV range, are well motivated in particle physics, but their status as dark-matter candidates is muddled by early-Universe uncertainties. We investigate how upcoming data from colliders may clarify this picture. Light gravitinos are produced primarily in the decays of the next-to-lightest supersymmetric particle, resulting in spectacular signals, including di-photons, delayed and nonpointing photons, kinked charged tracks, and heavy metastable charged particles. We find that the Tevatron with 20  fb^(-1) and the 7 TeV LHC with 1  fb^(-1) may both see evidence for hundreds of light-gravitino events. Remarkably, this collider data is also well suited to distinguish between currently viable light-gravitino scenarios, with striking implications for structure formation, inflation, and other early-Universe cosmology.
41299039
Observation of higher-order snake resonances in polarized proton acceleration in RHIC.
Higher-order and coupled snake resonances were observed during the 2002 polarized proton run in RHIC. Strong depolarization was observed when the fractional part of the vertical betatron tune approached 1/4, and when the fractional part of the horizontal tune approached 3/14. Because of the closed orbit error, each snake resonance splits into two. From the width of the observed snake resonances, we can derive the strength of the imperfection spin resonance. Our results appear consistent with the measured closed orbit error.
119519436
A dual gravity study of the (2+1)D compact U(1) gauge theory coupled with strongly interacting matter fields
Abstract We consider the D2-brane probe action in the gravity background dual to N coincident D p -branes by treating the separation between the D2- and D p -branes as a non-dynamical parameter for p = 2 , 4 , 6 . The gauge coupling, the core size of a non-BPS instanton and the mass gap of the compact U ( 1 ) gauge theory in the D2-brane are determined as a function of the separation in the type IIA gravity region. The results are interpreted in terms of the ( 2 + 1 ) D U ( 1 ) gauge theory coupled with the matter fields which are also strongly coupled with the ( p + 1 ) D SU ( N ) gauge field. It is shown that strong coupling of the matter fields to the SU ( N ) gauge field can drastically modify their screening of the U ( 1 ) gauge field. The non-perturbative dependence of the U ( 1 ) gauge coupling on the energy scale is obtained.
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.