Talks

I will discuss recent progress on the initial conditions for inflation and how this can potentially enhance gravitational wave non-Gaussianity (NG). In particular, there is a significant additional NG contribution in the flattened configuration, offering a straightforward way to boost parity-violating NG from Chern-Simons gravity, which typically suffers from graviton ghost-production. Furthermore, I will explore how this shape – at the level of the trispectrum – can enable direct measurement of NG in the stochastic gravitational wave background (SGWB) using pulsar timing arrays (PTA). This is particularly intriguing as it allows us to investigate NG at scales complementary to those observed in the CMB, which could help us distinguish between various early universe models and physical mechanisms.

CTCF-mediated chromatin loops play a crucial role in facilitating interactions between distal genomic regions. These loops have also been proposed to insulate enhancers from contacting with promoters in neighboring domains to prevent ectopic gene activation. However, the in vivo significance of this model has not been thoroughly tested. To test whether chromosome domains with higher density of developmental regulators are more susceptible to disruption of chromatin structure, we deleted a 25kb region containing four CTCF motifs at the boundary of a domain harboring the Fgf3, Fgf4, and Fgf15 loci. These genes with distinct spatiotemporal expression are critical for cell fate specification, patterning and organogenesis. Strikingly, heterozygous mutants showed perinatal lethality and encephalocele¬, a neural tube closure defect¬¬ caused by over-proliferation of neural tissue, abnormal cranial morphology, and skull bone hypoplasia. To confirm that these defects arise from loss of CTCF m...