Inflationary electroweak/particle phase transitions and new classical gravitational waves on CMB

Particle phase transitions in the early universe including electroweak and grand unification ones are well-studied subjects. We point out that there are new possible particle phase transitions around inflation. Those new inflationary particle phase transitions, if of the first order, may yield low-frequency gravitational waves (GWs) due to bubble dynamics, leaving imprints on the cosmic microwave background (CMB). In contrast to the nearly scale-invariant primordial GWs caused by vacuum fluctuation, these bubble-generated GWs are classical and have scale dependent B-mode spectra. If decoupled from inflaton, the electroweak phase transition during inflation may serve as a mirror image of the one after reheating where the baryon asymmetry could be generated via electroweak baryogenesis (EWBG). The second new electroweak phase transition may also be the source for EWBG.Comment: 6 pages, 4 figures, prepared for the proceeding of the 2nd LeCosPA Symposium "Everything About Gravity", based on arxiv:1512.0753

Spacetime as a topological insulator: Mechanism for the origin of the fermion generations

We suggest a mechanism whereby the three generations of quarks and leptons correspond to surface modes in a five-dimensional theory. These modes arise from a nonlinear fermion dispersion relation in the extra dimension, much in the same manner as fermion surface modes in a topological insulator or lattice implementation of domain wall fermions. We also show that the topological properties can persist in a deconstructed version of the model in four dimensions.Comment: Substantially revised version, to appear in Phys. Rev. Let

Finite size effects on the statistical angle of an electron induced dyon in proximity to a topological insulator

A pointlike electric charge close to the surface of a three dimensional topological insulator induces a magnetic monopole mirror charge. We study the distance dependence of the statistical angle describing this induced dyon system. We find that the total angular momentum, which sometimes is used as signature of the statistical angle, for an electron outside a finite size spherical or tube shaped topological insulator is zero for any finite distance between the electron and the surface. However, we show that in the 2-electron system one can indeed isolate a non-trivial statistical angle for intermediate size loops, that is loops much larger than the distance of the charge to the sample but much smaller than the size of the sample. The necessity for this limit confirms the 2+1 dimensional nature of the non-trivial statistical angle found in previous work. Our results clarify the conditions under which the statistical angle of this system could be measured in real experiments.Comment: 8 pages, 3 figure

Echoes of Inflationary First-Order Phase Transitions in the CMB

Cosmological phase transitions (CPTs), such as the Grand Unified Theory (GUT) and the electroweak (EW) ones, play a significant role in both particle physics and cosmology. In this letter, we propose to probe the first-order CPTs, by detecting gravitational waves (GWs) which are generated during the phase transitions through the cosmic microwave background (CMB). If happened around the inflation era, the first-order CPTs may yield low-frequency GWs due to bubble dynamics, leaving imprints on the CMB. In contrast to the nearly scale-invariant primordial GWs caused by vacuum fluctuation, these bubble-generated GWs are scale dependent and have non-trivial B-mode spectra. If decoupled from inflaton, the EWPT during inflation may serve as a probe for the one after reheating where the baryon asymmetry could be generated via EW baryogenesis (EWBG). The CMB thus provides a potential way to test the feasibility of the EWBG, complementary to the collider measurements of Higgs potential and the direct detection of GWs generated during EWPT.Comment: 5+6 pages, 4 figures. V2 changed title, added one figure about constraints of Planck2015+BICEP2/Keck data, added references and removed appendix. Accepted by PL

An O(750) GeV Resonance and Inflation

We study the possibility of a heavy scalar or pseudoscalar in TeV-scale beyond the Standard Model scenarios being the inflaton of the early universe in light of the recent O(750) GeV diphoton excess at the LHC. We consider a scenario in which the new scalar or pseudoscalar couples to the Standard Model gauge bosons at the loop level through new massive Standard Model charged vectorlike fermions with or without dark fermions. We calculate the renormalization group running of both the Standard Model and the new scalar couplings, and present two different models that are perturbative and with a stabilized vacuum up to near the Planck scale. Thus, the Standard Model Higgs and this possible new resonance may still preserve the minimalist features of Higgs inflation.Comment: 13 pages, 7 figures. v2 updated references and footnotes. Aligned with accepted version in PRD. v3 appendix recovere

Emergent Dark Matter in Late Time Universe on Holographic Screen

We discuss a scenario that the dark matter in late time universe emerges as part of the holographic stress-energy tensor on the hypersurface in higher dimensional flat spacetime. Firstly we construct a toy model with a de Sitter hypersurface as the holographic screen in the flat bulk. After adding the baryonic matter on the screen, we assume that both of the dark matter and dark energy can be described by the Brown-York stress-energy tensor. From the Hamiltonian constraint equation in the flat bulk, we find an interesting relation between the dark matter and baryonic matter's energy density parameters, by comparing with the Lambda cold dark matter parameterization. We further compare this holographic embedding of emergent dark matter with traditional braneworld scenario and present an alternative interpretation as the holographic universe. It can be reduced to our toy constraint in the late time universe, with the new parameterization of the Friedmann equation. We also comment on the possible connection with Verlinde's emergent gravity, where the dark matter is treated as the elastic response of the baryonic matter on the de Sitter spacetime background. We show that from the holographic de Sitter model with elasticity, the Tully-Fisher relation and the dark matter distribution in the galaxy scale can be derived.Comment: 28 pages, 2 figures; Matches published version and we thank the referees for many insightful comments; v3: typos in the Friedmann equations are fixe