289 research outputs found
The Equations of Motion of the Post-Newtonian Compact Binary Inspirals As Gravitational Radiation Sources Under The Effective Field Theory Formalism
The success of advanced LIGO/VIRGO detections of gravitational wave signals beginning in 2015 has opened a new window on the universe. Since April 2019, LIGO’s third observing run has identified binary merger candidates with a rate of roughly one per week. In order to understand the properties of all the candidates, it is necessary to construct large template banks of gravitational waveforms. Future upgrades of the LIGO detectors and the next generation detectors with better sensitivity post challenges to the current calculations of waveform solutions. The improvement of the systematic and statistical uncertainties calls for higher accuracy in waveform modeling. It is also crucial to include more physical effects and cover the full parameter space for the future runs.
This thesis focuses on the equations of motion of the post-Newtonian compact binary inspirals as gravitational wave sources. The second post-Newtonian order corrections to the radiation reaction is calculated using the Effective Field Theory formalism. The analytical solutions to the equations of motion and spin precession equations are obtained using the dynamical renormalization group method up to the leading order in spin-orbit effects and radiation reaction
Spin Effects in the Effective Field Theory Approach to Post-Minkowskian Conservative Dynamics
Building upon the worldline effective field theory (EFT) formalism for
spinning bodies developed for the Post-Newtonian regime, we generalize the EFT
approach to Post-Minkowskian (PM) dynamics to include rotational degrees of
freedom in a manifestly covariant framework. We introduce a systematic
procedure to compute the total change in momentum and spin in the gravitational
scattering of compact objects. For the special case of spins aligned with the
orbital angular momentum, we show how to construct the radial action for
elliptic-like orbits using the Boundary-to-Bound correspondence. As a
paradigmatic example, we solve the scattering problem to next-to-leading PM
order with linear and bilinear spin effects and arbitrary initial conditions,
incorporating for the first time finite-size corrections. We obtain the
aligned-spin radial action from the resulting scattering data, and derive the
periastron advance and binding energy for circular orbits. We also provide the
(square of the) center-of-mass momentum to , which may be used
to reconstruct a Hamiltonian. Our results are in perfect agreement with the
existent literature, while at the same time extend the knowledge of the PM
dynamics of compact binaries at quadratic order in spins.Comment: 41 pages. 1 ancillary file (wl format
Learning Feature Descriptors for Pre- and Intra-operative Point Cloud Matching for Laparoscopic Liver Registration
Purpose: In laparoscopic liver surgery (LLS), pre-operative information can
be overlaid onto the intra-operative scene by registering a 3D pre-operative
model to the intra-operative partial surface reconstructed from the
laparoscopic video. To assist with this task, we explore the use of
learning-based feature descriptors, which, to our best knowledge, have not been
explored for use in laparoscopic liver registration. Furthermore, a dataset to
train and evaluate the use of learning-based descriptors does not exist.
Methods: We present the LiverMatch dataset consisting of 16 preoperative
models and their simulated intra-operative 3D surfaces. We also propose the
LiverMatch network designed for this task, which outputs per-point feature
descriptors, visibility scores, and matched points.
Results: We compare the proposed LiverMatch network with anetwork closest to
LiverMatch, and a histogram-based 3D descriptor on the testing split of the
LiverMatch dataset, which includes two unseen pre-operative models and 1400
intra-operative surfaces. Results suggest that our LiverMatch network can
predict more accurate and dense matches than the other two methods and can be
seamlessly integrated with a RANSAC-ICP-based registration algorithm to achieve
an accurate initial alignment.
Conclusion: The use of learning-based feature descriptors in LLR is
promising, as it can help achieve an accurate initial rigid alignment, which,
in turn, serves as an initialization for subsequent non-rigid registration. We
will release the dataset and code upon acceptance
Gravitational radiation from inspiralling compact objects: Spin effects to fourth Post-Newtonian order
The linear- and quadratic-in-spin contributions to the binding potential and
gravitational-wave flux from binary systems are derived to
next-to-next-to-leading order in the Post-Newtonian (PN) expansion of general
relativity, including finite-size and tail effects. The calculation is carried
out through the worldline effective field theory framework. We find agreement
in the overlap with the available PN literature and test-body limit. As a
direct application, we complete the knowledge of spin effects in the evolution
of the orbital phase for aligned-spin circular orbits to fourth PN order. We
estimate the impact of the new results in the number of accumulated
gravitational-wave cycles. We find they will play an important role in
providing reliable physical interpretation of gravitational-wave signals from
spinning binaries with future detectors such as LISA and the Einstein
Telescope.Comment: 5 pages + supplemental material and references. 4 figures. 1
ancillary fil
Radiation Reaction for Non-Spinning Bodies at 4.5PN in the Effective Field Theory Approach
We calculate the 2 post-Newtonian correction to the radiation reaction
acceleration for non-spinning binary systems, which amounts to the 4.5
post-Newtonian correction to Newtonian acceleration. The calculation is carried
out completely using the effective field theory approach. The center-of-mass
corrections to the results are complicated and are discussed in detail.
Non-trivial consistency checks are performed and we compare with corresponding
results in the literature. Analytic results are supplied in the supplementary
materials.Comment: 23 pages. 1 ancillary file (wl format
Cerberus: Low-Drift Visual-Inertial-Leg Odometry For Agile Locomotion
We present an open-source Visual-Inertial-Leg Odometry (VILO) state
estimation solution, Cerberus, for legged robots that estimates position
precisely on various terrains in real time using a set of standard sensors,
including stereo cameras, IMU, joint encoders, and contact sensors. In addition
to estimating robot states, we also perform online kinematic parameter
calibration and contact outlier rejection to substantially reduce position
drift. Hardware experiments in various indoor and outdoor environments validate
that calibrating kinematic parameters within the Cerberus can reduce estimation
drift to lower than 1% during long distance high speed locomotion. Our drift
results are better than any other state estimation method using the same set of
sensors reported in the literature. Moreover, our state estimator performs well
even when the robot is experiencing large impacts and camera occlusion. The
implementation of the state estimator, along with the datasets used to compute
our results, are available at https://github.com/ShuoYangRobotics/Cerberus.Comment: 7 pages, 6 figures, submitted to IEEE ICRA 202
Phonemic Adversarial Attack against Audio Recognition in Real World
Recently, adversarial attacks for audio recognition have attracted much
attention. However, most of the existing studies mainly rely on the
coarse-grain audio features at the instance level to generate adversarial
noises, which leads to expensive generation time costs and weak universal
attacking ability. Motivated by the observations that all audio speech consists
of fundamental phonemes, this paper proposes a phonemic adversarial tack (PAT)
paradigm, which attacks the fine-grain audio features at the phoneme level
commonly shared across audio instances, to generate phonemic adversarial
noises, enjoying the more general attacking ability with fast generation speed.
Specifically, for accelerating the generation, a phoneme density balanced
sampling strategy is introduced to sample quantity less but phonemic features
abundant audio instances as the training data via estimating the phoneme
density, which substantially alleviates the heavy dependency on the large
training dataset. Moreover, for promoting universal attacking ability, the
phonemic noise is optimized in an asynchronous way with a sliding window, which
enhances the phoneme diversity and thus well captures the critical fundamental
phonemic patterns. By conducting extensive experiments, we comprehensively
investigate the proposed PAT framework and demonstrate that it outperforms the
SOTA baselines by large margins (i.e., at least 11X speed up and 78% attacking
ability improvement)
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