Hadron Ion Tea (HIT) Seminar
[formerly Heavy Ion Tea Seminar]
Nuclear Science Division
Lawrence Berkeley National Laboratory
09 Mar, 2021 -Urs Widemann (CERN) (1:30 pm)
16 Mar, 2021 - Xuan Li (LANL)
23 Mar, 2021 - Open
30 Mar, 2021 - Dima Kharzeev (SUNY@Stony Brook & BNL)
06 April, 2021 - JingFeng Liao (Indiana Univ)
13 April, 2021 - Xiaofeng Luo (Central China Normal University)
1 June, 2021 - Nu Xu (LBNL)
What can we learn from heavy neutron stars?
The observation of gravitational waves from a blackhole-mystery object binary opens the possibility for heavy neutron stars of 2.5 solar masses (potentially seen in GW190814). If this mystery object is a neutron star of 2.5 solar masses, it poses direct challenges to models of the equation of state. Interestingly, introducing non-trivial structure in the speed of sound sourced by changes in the degrees of freedom (possibly quarks) of ultra-dense matter can resolve this conflict, which may have large ramifications in nuclear and astrophysics. However, for a clear smoking gun signature of the mystery object being a neutron star, one requires a measurement of the tidal deformability that is non-zero. Because the predicted values are very small, a tenfold increase in sensitivity may be needed to test this possibility with gravitational waves, which is feasible with third generation detectors. Finally, I will comment on opportunities in heavy-ion collisions that exist for further constraining the equation of state relevant to neutron stars.
Tues. 2021.01.26, 1:30 PM, Virtual Zoom HIT
The phenomenon of anomaly plays an important role in quantum field theory. In QCD how axial anomaly manifests itself in the two-point correlation functions of iso-triplet scalar and pseudo-scalar mesons affects the nature of chiral phase transition. In this talk I first review current studies of the fate of UA (1) anomaly in the finite temperature lattice QCD, and then propose novel relations between the quark mass derivatives of Dirac eigenvalue spectrum and correlation functions among eigenvalues in order to study the microscopic origin of the axial anomaly. We finally show our results in the chiral and continuum limit in (2+1)-flavor lattice QCD at 1.6Tc. Our results suggest that the axial anomaly is driven by the weakly interacting (quasi-)instanton gas motived eigenvalue spectrum above 1.6Tc and the chiral phase transition is of 2nd order and belongs to 3-d O(4) universality class (talk is based on https://arxiv.org/abs/2010.14836).