Alternative Boundary Conditions in Asymptotically Anti-de Sitter Spacetimes

Posted by klaurent Chicago

Kavli Affiliate: Robert Wald | Summary:Anti-de Sitter (AdS) spacetimes are not globally hyperbolic, so boundary conditions are generally needed for well-defined dynamics. Ishibashi and Wald (IW) determined boundary conditions yielding well-posed dynamics with conserved positive energy for scalar, electromagnetic, and linearized gravitational fields, using nonlocal potentials and individual spherical harmonic modes. In this paper, we […]


Continue.. Alternative Boundary Conditions in Asymptotically Anti-de Sitter Spacetimes

Alternative Boundary Conditions in Asymptotically Anti-de Sitter Spacetimes

Posted by klaurent Chicago

Kavli Affiliate: Robert Wald | Summary:Anti-de Sitter (AdS) spacetimes are not globally hyperbolic, so boundary conditions are generally needed for well-defined dynamics. Ishibashi and Wald (IW) determined boundary conditions yielding well-posed dynamics with conserved positive energy for scalar, electromagnetic, and linearized gravitational fields, using nonlocal potentials and individual spherical harmonic modes. In this paper, we […]


Continue.. Alternative Boundary Conditions in Asymptotically Anti-de Sitter Spacetimes

Binary-black hole spin population results may be driven by prior degeneracies

Posted by klaurent MIT

Kavli Affiliate: Salvatore Vitale | Summary:Gravitational waves carry information on the spins of merging binary-black holes. The orientations of their spins relative to their orbits ("tilts")—while challenging to measure—differentiate the astrophysical formation mechanisms by which merging black hole binaries may form. Multiple analyses have reported tentative evidence that black hole spins are preferentially oriented in […]


Continue.. Binary-black hole spin population results may be driven by prior degeneracies

CypA is a molecular barrier to HIV emergence from Eastern chimpanzees

Posted by dbos Rockefeller

Kavli Affiliate: Michael W. Young | Authors: Michael J Young, Fabricio Cotera, Clare C. C. Gill, Jacob A. Lewis, Frank G. Whitby, Alaa Abdellatif, Joana L. Rocha, Michael Singer, Mike A Nalls, Faraz Faghri, Peter H Sudmant, Owen Pornillos and Molly Ohainle | Summary: Of the two lineages of lentivirus that endemically infect chimpanzees, only […]


Continue.. CypA is a molecular barrier to HIV emergence from Eastern chimpanzees

The CHIME/FRB Outriggers: Commissioning the Hat Creek Outrigger and an Updated Calibration Scheme for Mitigating RFI

Posted by klaurent MIT

Kavli Affiliate: Kiyoshi Masui | Summary:This work presents commissioning of the Hat Creek Outrigger (HCO), a dual-polarization 256-element radio interferometer that is part of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Outrigger project. Driven by a complex radio-frequency interference (RFI) environment that consistently contaminates $sim40%$ of HCO’s usable bandwidth, we implement an […]


Continue.. The CHIME/FRB Outriggers: Commissioning the Hat Creek Outrigger and an Updated Calibration Scheme for Mitigating RFI

A data processing pipeline for the WINTER near-infrared surveyor using the $textttmirar$ framework

Posted by klaurent MIT

Kavli Affiliate: Robert Simcoe | Summary:We present the data reduction and transient detection pipeline for the Wide-field Infrared Transient Explorer (WINTER) surveyor and report its on-sky performance. The WINTER camera utilizes cost-effective InGaAs sensors as alternatives to traditional IR sensors, and is mounted on a dedicated 1-m robotic telescope at Palomar Observatory. The WINTER camera […]


Continue.. A data processing pipeline for the WINTER near-infrared surveyor using the $textttmirar$ framework

Performance Comparison of the Nonlinear Curvature and Shack-Hartmann Wavefront Sensors in Strong Turbulence

Posted by klaurent Stanford

Kavli Affiliate: Arlene Aleman | Summary:Strong turbulence induces spatial variations in beam intensity that hinder the reconstruction process of many commonly deployed adaptive optics (AO) systems that use gradient-based wavefront sensors (WFS), such as the Shack-Hartmann wavefront sensor (SHWFS) and pyramid wavefront sensor. The nonlinear curvature WFS (nlCWFS) uses Fresnel diffraction to extract wavefront phase […]


Continue.. Performance Comparison of the Nonlinear Curvature and Shack-Hartmann Wavefront Sensors in Strong Turbulence

A Candidate Innermost Fifth Planet In the HR 8799 System Revealed By JWST NIRISS Aperture Masking Interferometry

Posted by klaurent Stanford

Kavli Affiliate: Bruce Macintosh | Summary:We detect a candidate fifth planet in the HR 8799 system, directly imaged with the JWST/NIRISS Aperture Masking Interferometer (AMI). The detected source lies just above a $3σ$ contrast curve at a contrast of $sim2times10^-4$ in the F380M filter at a projected separation of $sim150$ mas, corresponding to a few-to-several […]


Continue.. A Candidate Innermost Fifth Planet In the HR 8799 System Revealed By JWST NIRISS Aperture Masking Interferometry

Efficient LOS-Sampled GNSS Direct Position Estimation: An Information-Loss CRB Analysis

Posted by klaurent Caltech

Kavli Affiliate: Wei Gao| Summary:Conventional Global Navigation Satellite System (GNSS) Direct Position Estimation (DPE) exploits raw intermediate-frequency (IF) data and provides a full-information Cramér-Rao Bound (CRB) benchmark, but its accumulated-correlation objective requires dense evaluations over a common Position, Velocity, and Time (PVT) search space. This paper proposes an efficient Line-of-Sight (LOS)-sampled DPE, where each satellite […]


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Spatial sparse sampling-based iterative optimization framework for GNSS Direct Position Estimation

Posted by klaurent Caltech

Kavli Affiliate: Wei Gao| Summary:Direct position estimation (DPE), a promising technique in Global Navigation Satellite Systems (GNSS) receivers, enables estimation of position, velocity, and time (PVT) solutions directly from correlator outputs. The conventional grid search (GS)-based DPE is computationally intensive, as it relies solely on locating the peak of the cross ambiguity function (CAF), and […]


Continue.. Spatial sparse sampling-based iterative optimization framework for GNSS Direct Position Estimation