nesseris, savvas

In this review, we briefly summarize the so-called effective fluid approach, which is a compact framework that can be used to describe a plethora of different modified gravity models as general relativity (GR) and a dark energy (DE) fluid. This approach, which is complementary to the cosmological effective field theory, has several benefits, as it ...

Mars, Marc Sánchez-Pérez, Gabriel
Published in
Journal of Physics A: Mathematical and Theoretical

General hypersurfaces of any causal character can be studied abstractly using the hypersurface data formalism. In the null case, we write down all tangential components of the ambient Ricci tensor in terms of the abstract data. Using this formalism, we formulate and solve in a completely abstract way the characteristic Cauchy problem of the Einstei...

Liu, Yan-Yun Lv, Yu-Xiang Xue, Hai-Bin
Published in
Sensors (Basel, Switzerland)

The human radial artery pulse carries a rich array of biomedical information. Accurate detection of pulse signal waveform and the identification of the corresponding pulse condition are helpful in understanding the health status of the human body. In the process of pulse detection, there are some problems, such as inaccurate location of radial arte...

Bjerrum-Bohr, N. Emil J. Planté, Ludovic Vanhove, Pierre

In this chapter, we will review the field-theoretic treatment of General Relativity based on an effective field theory extension of the Einstein-Hilbert action. This pragmatic route to low-energy quantum effects in gravity critically underpins miscellaneous investigations of phenomenological and quantum extensions of General Relativity. We discuss ...

Bautista, Yilber Fabian Guevara, Alfredo Kavanagh, Chris Vinese, Justin

We continue to investigate correspondences between, on the one hand, scattering amplitudes for massive higher-spin particles and gravitons in appropriate quantum-to-classical limits, and on the other hand, classical gravitational interactions of spinning black holes according to general relativity. We first construct an ansatz for a gravitational C...

javed, wajiha atique, mehak pantig, reggie c. övgün, ali

In this study, we probe the weak lensing by a Reissner–Nordström black hole corrected by bounce parameter in plasma and dark matter mediums. For this, the optical geometry and the Gibbons–Werner approach are utilized to obtain the bending angle in the weak field limitations. We examine that the impact of these mediums increases the black hole’s ben...

He, Yutong Roper Pol, Alberto Brandenburg, Axel

We study the propagation of cosmological gravitational wave (GW) backgrounds from the early radiation era until the present day in modified theories of gravity. Comparing to general relativity (GR), we study the effects that Horndeski parameters, such as the run rate of the effective Planck mass $\alpha_{\rm M}$ and the tensor speed excess $\alpha_...

Chen, Po-Ning Paraizo, Daniel E Wald, Robert M Wang, Mu-Tao Wang, Ye-Kai Yau, Shing-Tung
Published in
Classical and Quantum Gravity

We introduce a notion of ‘cross-section continuity’ as a criterion for the viability of definitions of angular momentum, J, at null infinity: If a sequence of cross-sections, Cn , of null infinity converges uniformly to a cross-section C , then the angular momentum, J n , on Cn should converge to the angular momentum, J, on C . The Dray–Streubel (D...

Chen, Po-Ning Paraizo, Daniel E Wald, Robert M Wang, Mu-Tao Wang, Ye-Kai Yau, Shing-Tung
Published in
Classical and Quantum Gravity

We introduce a notion of ‘cross-section continuity’ as a criterion for the viability of definitions of angular momentum, J, at null infinity: If a sequence of cross-sections, , of null infinity converges uniformly to a cross-section , then the angular momentum, J n , on should converge to the angular momentum, J, on . The Dray–Streubel (DS) definit...

ricarte, angelo tiede, paul emami, razieh tamar, aditya natarajan, priyamvada

While supermassive black-hole masses have been cataloged across cosmic time, only a few dozen of them have robust spin measurements. By extending and improving the existing Event Horizon Telescope (EHT) array, the next-generation Event Horizon Telescope (ngEHT) will enable multifrequency, polarimetric movies on event-horizon scales, which will plac...