1,376 research outputs found
Scalar induced gravitational waves in symmetric teleparallel gravity with a parity-violating term
Gravitational waves (GWs) are useful to test gravitational theories and to
probe the physics in the early universe. In this paper, we investigate the
scalar induced gravitational waves (SIGWs) in symmetric teleparallel gravity
with a parity-violating term. The presence of the parity-violating term leads
to the velocity birefringence effect of the SIGWs. However, after taking into
account the observational constraints on the speed of GWs, the contribution
from the parity-violating term to SIGWs is negligible. Nevertheless, the
contribution to SIGWs from the perturbations of the connection can be
significant, and results in a multipeak structure in the energy density of
SIGWs. This feature makes the symmetric teleparallel gravity distinguishable
from the general relativity.Comment: 32 pages,2 figure
Scalar induced gravitational waves from Chern-Simons gravity during inflation era
We investigate the scalar induced gravitational waves (SIGWs) in the
Chern-Simons (CS) gravity with a dynamical scalar field during slow roll
inflation. Due to the parity violation in the CS term, the SIGWs are generally
polarized, which are effectively characterized by the degree of circular
polarization. We derive the semianalytic expression to evaluate the power
spectra and the degree of circular polarization of the SIGWs, which receive
contributions from the general relativity and the parity-violating term,
respectively. We find that the correction from the parity-violating CS term is
negligible on large scales, which means that the degree of circular
polarization of SIGWs is very small.Comment: 23 pages, references added, and a new discussion about a linear
coupling function added. Version to be published in JCA
Fenofibrate Enhances the In Vitro Differentiation of Foxp3+ Regulatory T Cells in Mice
Foxp3+ regulatory T cells (Tregs) play a critical role in maintaining immune self-tolerance. Reduced number and activity of Tregs are usually found in autoimmune and inflammatory diseases, and enhancing the differentiation of Tregs may be a promising therapeutic strategy. Some reports suggested an anti-inflammatory and anti-autoimmune potential for fenofibrate, a hypolipidemic drug used worldwide, whose lipid effects are mediated by the activation of peroxisome proliferator-activated receptor Ī± (PPARĪ±). In the present paper, we found that fenofibrate dose-dependently increased transforming growth factor-Ī² and interleukin-2-induced Treg differentiation in vitro, by 1.96-fold from 0 to 20āĪ¼M (12.59 Ā± 1.34% to 24.69 Ā± 3.03%, P < 0.05). Other PPARĪ± activators, WY14643 (100āĪ¼M), gemfibrozil (50āĪ¼M), and bezafibrate (30āĪ¼M), could not enhance Treg differentiation. In addition, PPARĪ± could not upregulate the promoter activity of the Treg-specific transcription factor Foxp3. Fenofibrate might exert its function by enhancing Smad3 phosphorylation, a critical signal in Treg differentiation, via Akt suppression. Our work reveals a new PPARĪ± independent anti-inflammatory mechanism of fenofibrate in up-regulating mouse Treg differentiation
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