10 research outputs found
Black Hole Photon Rings Beyond General Relativity
We investigate whether photon ring observations in black hole imaging are
able to distinguish between the Kerr black hole in general relativity and
alternative black holes that deviate from Kerr. Certain aspects of photon rings
have been argued to be robust observables in Very-Long-Baseline Interferometry
(VLBI) black hole observations which carry imprints of the underlying
spacetime. The photon ring shape, as well as its Lyapunov exponent (which
encodes the narrowing of successive photon subrings), are detailed probes of
the underlying geometry; measurements thereof have been argued to provide a
strong null test of general relativity and the Kerr metric. However, a more
complicated question is whether such observations of the photon ring properties
can distinguish between Kerr and alternative black holes. We provide a first
answer to this question by calculating photon rings of the Johannsen,
Rasheed-Larsen, and Manko-Novikov black holes. We find that large deviations
from Kerr and large observer inclinations are needed to obtain measurable
differences in the photon ring shape. In other words, the Kerr photon ring
shape appears to be the universal shape even for deviating black holes at low
inclinations. On the other hand, the Lyapunov exponent shows more marked
variations for deviations from the Kerr metric. Our analysis lays out the
groundwork to determine deviations from the Kerr spacetime in photon rings that
are potentially detectable by future observing missions.Comment: 31 pages + appendices; 20 figure
Modelling Giant Lipid Vesicles Designed for Light Energy Transduction
In this paper a deterministic kinetic model describing giant lipid vesicles designed for the transduction of light into chemical energy will be presented and discussed. Although the model is based on a simplified mechanism, kinetic constants taken from experimental measurements have been used. The obtained results have shown that giant vesicles encapsulating the Reaction Center in the lipid membrane can exhibit, in suitable experimental conditions, a sensible increase of the internal pH in half an hour under a constant light irradiation
Linac3, LEIR and PS Performance with Ions in 2021 and Prospects for 2022
CERN accelerators underwent a period of long shutdown from the end of 2018 to 2020. During this time frame, significant hardware and software upgrades have been put in place to increase the performance of both proton and ion accelerator chains in the High Luminosity LHC era. In the context of the CERN lead ion chain, 2021 has been mainly devoted to restore the injectors’ performance and to successfully prove the slip-stacking technique in SPS. In this paper we summarise the key milestones of the ion beam commissioning and the achieved beam performance for the Linac 3 (including the source), LEIR and PS accelerators, together with an outlook on 2022 operation
Waveform Modelling for the Laser Interferometer Space Antenna
International audienceLISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the beginnings of inspirals that will venture into the ground-based detectors' view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA's discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This white paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome
Waveform Modelling for the Laser Interferometer Space Antenna
International audienceLISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the beginnings of inspirals that will venture into the ground-based detectors' view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA's discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This white paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome
Waveform Modelling for the Laser Interferometer Space Antenna
International audienceLISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the beginnings of inspirals that will venture into the ground-based detectors' view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA's discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This white paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome