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## High Energy Phenomenology Seminar: Christina Gao (UIUC) "Stellar Remnants in the Presence of a Light Scalar"

Event Type
Seminar/Symposium
Department of Physics
Location
Via ZOOM
Virtual
Date
Oct 15, 2021   12:00 pm
Speaker
Christina Gao (UIUC)
Contact
Brandy Koebbe
E-Mail
BKOEBBE@ILLINOIS.EDU
Views
16
Originating Calendar
Physics - High Energy Phenomenology Seminar

We study how a Yukawa coupling of the Standard Model fermion to a light scalar effects the stellar structure of cold stellar remnants such as neutron stars.  We use a simple model of a massive scalar coupled to a single dominant fermion species with no other interactions. For a broad scalar mass range, the equation-of-state and stellar structure depends only the effective coupling $g_{eff}=g_f m_f / m_\phi$, where $g_f$ is the Yukawa coupling, $m_f$ the fermion mass and $m_\phi$ the scalar mass. If the effective coupling g_{eff} is larger than O(1) the Yukawa coupled matter exhibits various anomalous behaviors including hydrodynamic instability, negative pressure, distinct phases (soft and hard) of matter with sharp phase boundaries between them and with vacuum.  These anomalies can lead to stars exhibiting an unusual mass-radius relation compared to that predicted by Oppenheimer-Volkoff model. To the extent that these anomalies have not and/or will not be observed limits the size of the new Yukawa coupling.