Modeling dynamical scalarization with a resummed post-Newtonian expansion

Despite stringent constraints set by astrophysical observations, there remain viable scalar-tensor theories that could be distinguished from general relativity with gravitational-wave detectors. A promising signal predicted in these alternative theories is dynamical scalarization, which can dramatically affect the evolution of neutron-star binaries near merger. Motivated by the successful treatment of spontaneous scalarization, we develop a formalism that partially resums the post-Newtonian expansion to capture dynamical scalarization in a mathematically consistent manner. We calculate the post-Newtonian order corrections to the equations of motion and scalar mass of a binary system. Through comparison with quasi-equilibrium configuration calculations, we verify that this new approximation scheme can accurately predict the onset and magnitude of dynamical scalarization.Comment: 24 pages, 8 figures; recolored figures, fixed typos, added emai

Structures 2 - The response of a clamped circular plate to impulsive loads

Computer analysis of clamped circular plate response to axisymmetric impulsive loa

Structures i- the response of beams and rings to high-intensity, short-duration loading

Computer programs for determining response of beams and rings to high intensity, short duration loadin

Concentrating minds: how the Greeks designed spaces for public debate

What can we learn from ancient Greece when it comes to designing spaces for political debate? In an article for Theatrum Mundi, Richard Sennett describes how ancient Athenians used amphitheatres and the agora to debate, take decisions and participate in public life. He recalls Aristotle’s notion of how a complex urban society could reconcile differences. Modern societies – where concentrating on a political question has become ever more difficult – need public spaces conducive to focus and deliberation

Hairy binary black holes in Einstein-Maxwell-dilaton theory and their effective-one-body description

In General Relativity and many modified theories of gravity, isolated black holes (BHs) cannot source massless scalar fields. Einstein-Maxwell-dilaton (EMd) theory is an exception: through couplings both to electromagnetism and (non-minimally) to gravity, a massless scalar field can be generated by an electrically charged BH. In this work, we analytically model the dynamics of binaries comprised of such scalar-charged ("hairy") BHs. While BHs are not expected to have substantial electric charge within the Standard Model of particle physics, nearly-extremally charged BHs could occur in models of minicharged dark matter and dark photons. We begin by studying the test-body limit for a binary BH in EMd theory, and we argue that only very compact binaries of nearly-extremally charged BHs can manifest non-perturbative phenomena similar to those found in certain scalar-tensor theories. Then, we use the post-Newtonian approximation to study the dynamics of binary BHs with arbitrary mass ratios. We derive the equations governing the conservative and dissipative sectors of the dynamics at next-to-leading order, use our results to compute the Fourier-domain gravitational waveform in the stationary-phase approximation, and compute the number of useful cycles measurable by the Advanced LIGO detector. Finally, we construct two effective-one-body (EOB) Hamiltonians for binary BHs in EMd theory: one that reproduces the exact test-body limit and another whose construction more closely resembles similar models in General Relativity, and thus could be more easily integrated into existing EOB waveform models used in the data analysis of gravitational-wave events by the LIGO and Virgo collaborations.Comment: 36 pages, 12 figures, updated to match published versio