Session F03: Astrophysics and General Physics

Relativistic Tidal Deformations of Neutron Stars with Hybrid Equations of States

An exploration of how the tidal properties measured in gravitational waves (GWs) from coalescing neutron stars can be utilized to constrain the elusive neutron star (NS) equation of state (EoS) was conducted. Realistic EoS models that featured phase transitions to quark matter, governed by the vector interaction enhanced BAG (vBAG) model, were employed to simulate behavior that is more consistent with quantum chromodynamics (QCD) calculations. From these models, relations between the mass-weighted tidal deformability, Λeff, and the binary mass ratio, q = M2/M1, were analyzed to determine if a given EoS, meets the criterion determined by the GW170817 signal of 400 ≤ Λeff ≤ 800 for 0.7 ≤ q ≤ 1.0. By analyzing the tidal deformability of a single star, Λ, under the condition that Λ(1.4Msolar) ≤ 800 and 2.01Msolar ≤ max(M) ≤ 2.16Msolar, constraints to the EoS of the strongly-interacting dense matter on the interiors of NSs can be placed. We find that nuclear models of EoS with Λ(1.4Msolar) > 800 cannot easily be ruled out because a transition to quark matter can occur, which would result in a more compact hybrid configuration--thus a lower Λ.    

Coarse-Graining for Coupled Oscillators: A case study in discovering low-dimensional dynamics

Quantitative science has produced successful models of the 
world at scales spanning dozens of orders of magnitude in space, time, 
and energy. While in principle, the most finely detailed models are 
sufficient to reproduce the predictions of any less-detailed model, 
there is clearly scientific value in deriving and studying models that 
do not resolve details that are not directly relevant to the question at 
hand. The procedure of systematically reducing the degrees of freedom of 
a model goes by many names depending on context (renormalization group 
in statistical physics) but can be generally be referred to as "model 
reduction". In this talk I will discuss progress towards general 
principles of model reduction obtained by studying synchronization of 
phase oscillators on a modular network. This system is an ideal test-bed 
because it exhibits a controllable transition from high- to 
low-dimensional behavior; moreover, the resulting low-dimensional 
behavior is well-described by coarse-grained equations of a known form.   

Higher-dimernsional quantum hypergraph-product codes

The quantum hypergraph-product codes by Tillich and Zemor, and m-dimensional toric codes could be generalized into one family of codes. Those codes are isomorphic to the CSS codes generated by m-chain complex. A recursive formula is given for such construction, with explicit code parameters. This work is useful for constructing fault-tolerant quantum LDPC codes.