=============== journal club meeting ===============
Time: Friday 11:00-12:00 (KST)
Place: Room 1423
- Talk Information
Talk1
Speaker: Mr. Heejoo Kim (KAIST; visiting talk)
Title: More Scalings from Cosmic Strings
Abstract: We conduct lattice simulations to estimate the abundance of axion dark matter radiated from global cosmic strings in a post-inflationary scenario. We provide independent numerical confirmation of the recently observed logarithmic growth in both the number of strings per Hubble patch and the spectral index of the power law scaling for the axion spectrum. These logarithmic scalings are examined under two sets of initial conditions: one with a well-developed string network configuration and the other with a thermal field configuration. We discuss a significant correlation between the axion spectrum and string evolution under different initial conditions, which supports the insensitivity of scaling behaviors to variations in initial data, and we provide a qualitative understanding of this relationship. The impact of various combinations of the power law of the axion spectrum, nonlinearities around the QCD scale, and average inter-string distances on axion abundance is also addressed. Additionally, we derive a lower bound on the axion mass based on a benchmark choice. A novel method for string identification is developed, utilizing the tetrahedralization of space, which ensures the connectedness of the strings and facilitates the assignment of core locations. We analyze individual cosmic strings of varying lengths within a large ensemble of cosmic string networks. Notably, we report strong evidence for a logarithmically growing spectral index of the string power spectrum during evolution, which may significantly support the observed logarithmic growth of the spectral index of the axion spectrum.
Talk 2
Speaker:
Title:
References:
===========lunch polling===============
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TaeHun Kim