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DTSTAMP:20260429T073643
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SUMMARY:Special Double feature Virtual INPA seminar  | Anton Baleato Lizancos (Cambridge) and Utkarsh Giri (PITP)
DESCRIPTION:Speaker: Anton Baleato Lizancos (Cambridge) \nTitle: “Understanding biases to CMB lensing and delensing on the road to precision science” \nAbstract: For cosmologists\, CMB lensing can be both a blessing and a nuisance. It’s a nuisance because it generates spurious B-mode polarisation which obscures the highly-sought-after signal from inflationary gravitational waves\, but it’s a blessing because it can be used to reconstruct maps of the projected matter distribution of the Universe\, from which any physics affecting the growth of cosmic structure can be constrained. In this talk\, I will focus on systematics that need to be addressed in order to harness the full statistical power of upcoming CMB experiments and make progress in both of these exciting areas. In the first part of my talk\,  I will briefly review the ways in which extragalactic emission from galaxies and clusters can bias CMB lensing reconstruction power spectra and cross-correlations with other tracers of the matter distribution. I will then present ongoing work on a novel approach where we model these biases analytically as a function of experimental characteristics\, enabling improved physical insight\, a quantification of theoretical uncertainties and potentially opening the door to improved mitigation methods. In the second part of the talk\, I will explain how the lensing contamination to CMB B-modes can be removed — what is known as delensing — in order to facilitate searches for inflationary gravitational waves\, and describe limitations of the commonly-used “template” approach to delensing. I will then briefly summarize preparatory efforts to delens data from the upcoming Simons Observatory. Finally\, I will conclude by discussing biases affecting the procedure (and how to mitigate them) when lensing is reconstructed internally from the CMB itself\, and in the alternative scenario where the CIB is used as a tracer of the matter. \nSpeaker: Utkarsh Giri (Perimeter Institute of Theoretical Physics)  \nTitle: “Exploring kSZ velocity reconstruction with N-body simulations and the halo model” \nAbstract:  \nKSZ velocity reconstruction is a recently proposed method for mapping the largest-scale modes of the universe\, by applying a quadratic estimator v̂ to the small-scale CMB and a galaxy catalog. We implement kSZ velocity reconstruction in an N-body simulation pipeline and explore its properties. We find that the reconstruction noise can be larger than the analytic prediction which is usually assumed. We revisit the analytic prediction and find additional noise terms that explain the discrepancy. The new terms are obtained from a six-point halo model calculation\, and are analogous to the N(1) and N(3/2) biases in CMB lensing. We implement an MCMC pipeline which estimates fNL from N-body kSZ simulations and show that it recovers unbiased estimates of fNL\, with statistical errors consistent with a Fisher matrix forecast. Overall\, these results confirm that kSZ velocity reconstruction will be a powerful probe of cosmology in the near future\, but new terms should be included in the noise power spectrum. \nJoin Zoom Meeting: https://lbnl.zoom.us/j/97706913102?pwd=QVl4M0xScklRbUwyVXNVbkF2R0tDUT09 \nMeeting ID: 977 0691 3102 \nPasscode: 505782 505782 \nAbstract: https://inpa.lbl.gov/event/special-double-f…tkarsh-giri-pitp/
URL:https://inpa.lbl.gov/event/special-double-feature-virtual-inpa-seminar-anton-baleato-lizancos-cambridge-and-utkarsh-giri-pitp/
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DTSTART;TZID=America/Los_Angeles:20201120T120000
DTEND;TZID=America/Los_Angeles:20201120T130000
DTSTAMP:20260429T073643
CREATED:20201109T005051Z
LAST-MODIFIED:20201113T222559Z
UID:920-1605873600-1605877200@inpa.lbl.gov
SUMMARY:VIRTUAL INPA SEMINAR | Liang Dai (UCB)
DESCRIPTION:Speaker: Liang Dai (UC Berkeley) \nTitle: A New Window Into the Universe: Gravitational Waves From Compact Binary Coalescence \n Abstract: \nDetection of chirping gravitational waves (GWs) at ground-based laser interferometry observatories LIGO and Virgo have uncovered a population of compact binary mergers. Forthcoming observing runs with upgraded sensitivity and more observatories joining the network will tremendously increase the number of source systems\, which will shed light on their astrophysical origin and enable to exploit those events as cosmological probes. I will present independent efforts by the IAS group to analyze the publicly available LIGO/Virgo data and report newly discovered GW events in addition to what experimental collaborations have reported. I will highlight several original and crucial data analysis methodologies we have developed for template matching\, noise characterization and parameter estimation. In addition\, I will give outlook on gravitational lensing of cosmological GW sources as expected from forthcoming observations and envisage its applications. I will explain our new findings of how wave propagation effects\, measurable with GWs but unfeasible with usual electromagnetic sources\, can allow extraction of unique information to reconstruct the lens or to probe non-luminous sub-galactic dark matter structures\, thereby deepening our understanding of the matter distribution in the Universe. \nJoin Zoom Meeting\nhttps://lbnl.zoom.us/j/95757502382?pwd=bkdDbGx4NlVKUGVkY0NYVE85Y2RuZz09\nMeeting ID: 957 5750 2382\nPasscode: 554719
URL:https://inpa.lbl.gov/event/virtual-inpa-seminar-liang-dai-ucb/
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