## "Tidal Love numbers: from black holes to exotic physics"Valerio De Luca
, University of Pennsylvania
[Host: Kent Yagi]
ABSTRACT:
Tidal Love numbers describe the linear response of compact objects to external tidal perturbations, and they are found to vanish exactly for black holes within General Relativity. We first discuss the robustness of this property when non-linearities in the theory are taken into account, and then investigate the scenario of black holes dressed with an ultralight scalar field, addressing their detectability at future gravitational wave experiments. Finally, we discuss the tidal deformability of more exotic compact objects, showing the relevance of universality relations as a way to distinguish between them. |
Gravity SeminarMonday, June 3, 2024 1:30 PM Physics, Room 323 Note special room. Join Zoom Meeting https://virginia.zoom.us/j/92692915873?pwd=RBHqSluEzZauAN6a40yhaDnyq2q0eh.1 Meeting ID: 926 9291 5873 Passcode: 503528 |

## "Unraveling the mysteries of strong gravity by employing electromagnetic and gravitational memory."Susmita Jana
, Indian Institute of Technology Bombay
[Host: David Nichols]
ABSTRACT:
The gravitational memory effect and its electromagnetic (EM) analog are potential probes in the strong gravity regime. In the literature, this effect is derived for static observers at asymptotic infinity. While this is a physically consistent approach, it restricts us to deriving memory for an asymptotically flat spacetime. In this talk, I will discuss how we evaluate EM and gravitational memory with respect to a comoving observer (defined by timelike 4-velocity u_{a}). We split 4-D the spacetime into 1+1+2 parts, consisting of one timelike, one preferred spacelike, and one 2-D hypersurface. It allows us to obtain EM memory in an arbitrary curved background spacetime and gravitational memory in a class of spacetime with spherical symmetry often referred to as Locally Rotationally Symmetric(LRS) type II in covariant formalism. The master equation corresponding to the acceleration of the comoving observer in the 2D surface provides a physical understanding of the EM memory. The leading order contribution to the EM memory comes from the total energy density of the EM field, while the subleading contributions contain the spacetime geometry and the other components of the energy-momentum tensor of the EM field. In the case of gravitational memory, we show it is manifested in the integral of the shear tensor of the 2-D hypersurface. We obtain the master equation of gravitational memory in LRS-II spacetime and finally, we show that the memory exhibits distinct signatures between accelerated and decelerated universes, potentially enabling the identification of the transition redshift from a matter-dominated to a dark-energy-dominated universe. In the end(if time permits), I will briefly discuss the generation of detectable GW from the interaction of very high energized EM wave and stellar-mass Schwarzschild black holes in the Milky Way galaxy. |
Gravity SeminarTuesday, June 4, 2024 10:00 AM Physics, Room 323 Note special date. Note special time. Note special room. Join Zoom Meeting https://virginia.zoom.us/j/99737910818?pwd=kW5bNj2Iwh2XmEaZuamMbWZ6AjsH8a.1 Meeting ID: 997 3791 0818 Passcode: 609195 |

## "Can self-interaction in supernova neutrinos cause changes in gravitational memory signals?"Indranil Chakraborty
, Indian Institute of Technology Bombay
[Host: David Nichols]
ABSTRACT:
Gravitational wave memory is a persistent non-oscillatory shift in the gravitational wave amplitude. Such effects are ubiquitous in astrophysical and cosmological cataclysmic events involving gravitational radiation. In this talk, we turn our attention to the case of a supernova neutrino burst generating gravitational radiation. Previous studies along this line have demonstrated that a neutrino burst in such scenarios gives rise to a gravitational memory signal. Here, we specifically inquire about the alterations to the memory signal when neutrinos emitted from a supernova undergo self-interaction, presenting an avenue for indirectly detecting neutrino self-interaction. |
Gravity SeminarThursday, June 6, 2024 2:00 PM Physics, Room 031 Note special date. Note special time. Note special room. Join Zoom Meeting: https://virginia.zoom.us/j/99737910818?pwd=kW5bNj2Iwh2XmEaZuamMbWZ6AjsH8a.1 Meeting ID: 997 3791 0818 Passcode: 609195 |

To add a speaker, send an email to dn2ep@Virginia.EDU Include the seminar type (e.g. Gravity Seminars), date, name of the speaker, title of talk, and an abstract (if available). [Please send a copy of the email to phys-speakers@Virginia.EDU.]