[Okc-wp4] EO seminar on the 5th of October: Tidal Deformability of Neutron Stars in Scalar-Tensor Theories of Gravity for Gravitational Wave Analysis

[Haakon Andresen]

Dear everyone,

This weeks seminar will be held by one of the most recent additions to the EO group, Alex Brown. The presentation
will focus on material published here https://arxiv.org/abs/2210.14025
I look forward to seeing you all there, zoom can be setup upon request. Let me know if you are away and still
would like to attend. We will meet in A5:1003, as last time.

All events are now in the calendar, which you can find here https://indico.fysik.su.se/category/289/
It can easily be imported into any calendar software.

Speaker: Stephanie (Alex) Brown
Title: Tidal Deformability of Neutron Stars in Scalar-Tensor Theories of Gravity for Gravitational Wave Analysis
Room: A5:1003
Abstract: Gravitational waves from compact binary coalescences are valuable for testing theories of gravity in the strong-field regime.
They have also led to improved constraints on the nuclear equation of state at extreme
densities by measuring the tidal Love numbers of merging neutron stars.
Tidal Love numbers in alternate theories are expected to differ from their general relativistic counterpart.
Despite this, tests of general relativity use the general relativistic tidal Love numbers.
Here, we calculate the $l\geq 2$ electric and magnetic tidal Love numbers for non-rotating stars in mono-scalar-tensor
theories assuming spontaneous scalarization. We then use several viable equations of state to explore how the mass, radius, and tidal deformability
relations differ from those of general relativity. The electric tidal deformability can differ by $\sim 350\%$, and the magnetic tidal deformability differs by $\sim 200 \%$.
These deviations occur at large compactnesses ($C = M/r > 0.2$) and vary slightly depending on the equation of state. Lastly, we perform Bayesian parameter
estimation of GW170817 to explore exactly how these modified tidal relations can effect inference.
We find that tidal Love numbers and tidal deformabilities can differ significantly from those in general relativity. These changes cause the inferred equation of state to differ
between general relativity and scalar tensor theory.
Applying these tidal Love numbers to the study of gravitational waves will allow for more consistent and accurate tests of scalar modes in gravitational waves from neutron star mergers.

Best,
Haakon (on behalf of the organizers of the EO meeting)

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