119262609
Time-dependent Ginzburg–Landau equation in the Nambu–Jona-Lasinio model
We apply the closed time-path Green function formalism in the Nambu-Jona-Lasinio model. First of all, we use this formalism to obtain the well-known gap equation for the quark condensate in a stationary homogeneous system. We have also used this formalism to obtain the Ginzburg Landau (GL) equation and the time-dependent Ginzburg Landau (TDGL) equation for the chiral order parameter in an inhomogeneous system. In our derived GL and TDGL equations, there is no other parameters except for those in the original NJL model. (C) 2010 Elsevier B.V. All rights reserved.
119262609
Time-dependent Ginzburg–Landau equation in the Nambu–Jona-Lasinio model
We apply the closed time-path Green function formalism in the Nambu-Jona-Lasinio model. First of all, we use this formalism to obtain the well-known gap equation for the quark condensate in a stationary homogeneous system. We have also used this formalism to obtain the Ginzburg Landau (GL) equation and the time-dependent Ginzburg Landau (TDGL) equation for the chiral order parameter in an inhomogeneous system. In our derived GL and TDGL equations, there is no other parameters except for those in the original NJL model. (C) 2010 Elsevier B.V. All rights reserved.
121474555
Constraints on the Cardassian expansion models from the latest observational data
We study observational constraints on Cardassian expansion models that account for the accelerated expansion of the universe via modification of the Friedmann equation. We find significant constraints on the model parameters using the latest type Ia supernovae, the baryon acoustic peak in the large scale correlation function of the Sloan Digital Sky Survey of luminous red galaxies, the cosmic microwave background radiation shift parameter, the x-ray gas mass fractions in clusters of galaxies and the observational H(z) data. In the original Cardassian model, we find Ωm = 0.27 ± 0.03, n = 0.01 ± 0.09 at the 1σ confidence level. This result is consistent with the flat ΛCDM cosmology. In the modified polytropic Cardassian model, we obtain β = 0.27−0.25+3.65 and n = −1.86−4.20+2.26(1σ). We also find that the acceleration happens for zT = 0.70 ± 0.05(1σ) in the original Cardassian model. In the modified polytropic Cardassian model, the transition redshift is zT = 0.58−0.18+0.17(1σ).
111221941
ASTROD and ASTROD I: Progress Report
Over the next decade the gravitational physics community will benefit from dramatic improvements in many technologies critical to the tests of gravity and gravitational-wave detection. The highly accurate deep space navigation, interplanetary laser ranging and communication, interferometry and metrology, high precision frequency standards, precise pointing and attitude control, together with the drag-free technologies will revolutionize the field of the experimental gravitational physics. Deep-space laser ranging will be ideal for gravitational-wave detection, and testing relativity and measuring solar-system parameter to an unprecedented accuracy. ASTROD I is such a mission with single spacecraft; it is the first step of ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) with 3 spacecraft. In this paper, we will present the progress of ASTROD and ASTROD I with emphases on the acceleration noises, mission requirement, charging simulation, drag-free control and low-frequency gravitational-wave sensitivity.
119254658
Deviation from the Cosmological Constant or Systematic Errors
In the work of Qi, Wang & Lu, gamma-ray bursts (GRBs) are used together with an earlier Type Ia supernova (SN Ia) data set to constrain the dark energy equation of state (EOS) in a nearly model-independent way. The improvements made by including GRBs show a slight shift of the dark energy EOS toward w > -1 at redshifts z greater than or similar to 0.5. It is interesting that, when we have more SNe Ia, SNe Ia themselves also show the same trend. Motivated by the fact that both SNe Ia and GRBs seem to prefer a dark energy EOS greater than -1 at redshifts z greater than or similar to 0.5, we perform a careful investigation of this situation, including more careful treatments of measurement errors of GRBs and cross-checking the results by using different ways of including GRBs. We find that the deviation of dark energy from the cosmological constant at redshifts z greater than or similar to 0.5 is large enough that we should pay close attention to it with future observational data. Such a deviation may arise from some biasing systematic errors in the handling of SNe Ia and/or GRBs, or more interestingly from the nature of the dark energy itself.
118390986
Testing the local-void alternative to dark energy using galaxy pairs
The possibility that we live in a special place in the universe, close to the center of a large, radially inhomogeneous void, has attracted attention recently as an alternative to dark energy or modified gravity to explain the accelerating universe. We show that the distribution of orientations of galaxy pairs can be used to test the Copernican principle that we are not in a central or special region of Universe. The popular void models can not fit both the latest type Ia supernova, cosmic microwave background data and the distribution of orientations of galaxy pairs simultaneously. Our results rule out the void models at the $4\sigma$ confidence level as the origin of cosmic acceleration and favor the Copernican principle.
118854953
High-redshift star formation rate up to z~8.3 derived from gamma-ray bursts and influence of background cosmology
The high-redshift star formation rate (SFR) is difficult to measure directly even by modern approaches. Long-duration gamma-ray bursts (GRBs) can be detected to the edge of the visible universe because of their high luminosities. The collapsar model of long GRBs indicates that they may trace the star formation history. So, long GRBs may be a useful tool of measuring the high-redshift SFR. Observations show that long GRBs prefer to form in a low-metallicity environment. We study the high-redshift SFR up to z∼ 8.3 considering the Swift GRBs tracing the star formation history and the cosmic metallicity evolution in different background cosmological models including Λ cold dark matter (ΛCDM), quintessence, quintessence with a time-varying equation of state and brane-world model. We use latest Swift GRBs including two highest-z GRBs, GRB 080913 at z= 6.7 and GRB 090423 at z= 8.3. We find that the SFR at z > 4 shows a steep decay with a slope of ∼−5.0 in ΛCDM. In the other three models, the high-redshift SFR is slightly different from ΛCDM model and also shows a steep decay.