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SUMMARY:Ultralight Dark Matter Background: Waking\, Shaking\, and Detectin
 g
DTSTART:20261001T060000Z
DTEND:20261001T070000Z
DTSTAMP:20260929T030900Z
UID:indico-event-19136@indico.global
DESCRIPTION:Speakers: Xucheng Gan\n\nUltralight dark matter (ULDM) that in
 duces variations of fundamental constants is well motivated by a variety o
 f UV models and provides an excellent target for rapidly advancing precisi
 on measurements. While linear interactions have been extensively studied\,
  quadratic scalar couplings remain much less constrained and arise natural
 ly in many theories. Importantly\, they can generate qualitatively new sig
 natures through background-induced effects.In this talk\, I will introduce
  two major classes of background-induced effects: wake forces and oscillat
 ory forces. For wake forces\, I will present a complete framework that uni
 fies previous approaches developed for different regions of parameter spac
 e. I will then apply this framework to the MICROSCOPE satellite\, a leadin
 g space-based test of the equivalence principle. The Earth's screening eff
 ect redistributes the directional dark matter wind\, while the satellite's
  orbital motion modulates the resulting signal\, imprinting a characterist
 ic frequency-band structure with annual modulation that provides a distinc
 tive fingerprint and substantially improves the sensitivity. For oscillato
 ry forces\, I will discuss two distinct signatures in gravitational-wave o
 bservatories: a coherent signal at the second harmonic of the ULDM oscilla
 tion and a stochastic beat signal arising from interference among differen
 t ULDM modes. I will focus on pulsar timing arrays (PTAs)\, which currentl
 y provide leading sensitivity\, and the future flagship space-based observ
 atory\, the Laser Interferometer Space Antenna (LISA)\, where screening is
  absent. Together\, these two classes of background-induced effects provid
 e complementary precision probes of quadratically coupled ultralight dark 
 matter through late-Universe measurements.\n\nhttps://indico.global/event/
 19136/
URL:https://indico.global/event/19136/
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