246 research outputs found
3DFeat-Net: Weakly Supervised Local 3D Features for Point Cloud Registration
In this paper, we propose the 3DFeat-Net which learns both 3D feature
detector and descriptor for point cloud matching using weak supervision. Unlike
many existing works, we do not require manual annotation of matching point
clusters. Instead, we leverage on alignment and attention mechanisms to learn
feature correspondences from GPS/INS tagged 3D point clouds without explicitly
specifying them. We create training and benchmark outdoor Lidar datasets, and
experiments show that 3DFeat-Net obtains state-of-the-art performance on these
gravity-aligned datasets.Comment: 17 pages, 6 figures. Accepted in ECCV 201
State/Operator Correspondence in Higher-Spin dS/CFT
A recently conjectured microscopic realization of the dS/CFT
correspondence relating Vasiliev's higher-spin gravity on dS to a Euclidean
CFT is used to illuminate some previously inaccessible aspects of
the dS/CFT dictionary. In particular it is argued that states of the boundary
CFT on are holographically dual to bulk states on geodesically
complete, spacelike slices which terminate on an at future
infinity. The dictionary is described in detail for the case of free scalar
excitations. The ground states of the free or critical model are dual
to dS-invariant plane-wave type vacua, while the bulk Euclidean vacuum is dual
to a certain mixed state in the CFT. CFT states created by operator
insertions are found to be dual to (anti) quasinormal modes in the bulk. A norm
is defined on the bulk Hilbert space and shown for the scalar case to be
equivalent to both the Zamolodchikov and pseudounitary C-norm of the
CFT.Comment: 24 page
Ground Processing of Cassini RADAR Imagery of Titan
The Cassini RADAR instrument onboard
the Cassini Orbiter is currently collecting
SAR Imagery of the surface of Saturn's largest
moon, Titan. This paper describes the ground
processing of Cassini SAR data. We focus upon the
unusual features of the data and how these features
impact the processing. We exhibit a data dependent
mechanism we have implemented for eliminating
artifacts due to attitude and ephemeris knowledge
error. Finally we describe how we trade-off SAR
performance vs. area of coverage when we design
our spacecraft pointing profiles
Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars
Lobate features abutting massifs and escarpments in the middle latitudes of Mars have been recognized in images for decades, but their true nature has been controversial, with hypotheses of origin such as ice-lubricated debris flows or glaciers covered by a layer of surface debris. These models imply an ice content ranging from minor and interstitial to massive and relatively pure. Soundings of these deposits in the eastern Hellas region by the Shallow Radar on the Mars Reconnaissance Orbiter reveal radar properties entirely consistent with massive water ice, supporting the debris-covered glacier hypothesis. The results imply that these glaciers formed in a previous climate conducive to glaciation at middle latitudes. Such features may collectively represent the most extensive nonpolar ice yet recognized on Mars
CHILES: HI morphology and galaxy environment at z=0.12 and z=0.17
We present a study of 16 HI-detected galaxies found in 178 hours of
observations from Epoch 1 of the COSMOS HI Large Extragalactic Survey (CHILES).
We focus on two redshift ranges between 0.108 <= z <= 0.127 and 0.162 <= z <=
0.183 which are among the worst affected by radio frequency interference (RFI).
While this represents only 10% of the total frequency coverage and 18% of the
total expected time on source compared to what will be the full CHILES survey,
we demonstrate that our data reduction pipeline recovers high quality data even
in regions severely impacted by RFI. We report on our in-depth testing of an
automated spectral line source finder to produce HI total intensity maps which
we present side-by-side with significance maps to evaluate the reliability of
the morphology recovered by the source finder. We recommend that this become a
common place manner of presenting data from upcoming HI surveys of resolved
objects. We use the COSMOS 20k group catalogue, and we extract filamentary
structure using the topological DisPerSE algorithm to evaluate the \hi\
morphology in the context of both local and large-scale environments and we
discuss the shortcomings of both methods. Many of the detections show disturbed
HI morphologies suggesting they have undergone a recent interaction which is
not evident from deep optical imaging alone. Overall, the sample showcases the
broad range of ways in which galaxies interact with their environment. This is
a first look at the population of galaxies and their local and large-scale
environments observed in HI by CHILES at redshifts beyond the z=0.1 Universe.Comment: 23 pages, 12 figures, 1 interactive 3D figure, accepted to MNRA
Spintronics: Fundamentals and applications
Spintronics, or spin electronics, involves the study of active control and
manipulation of spin degrees of freedom in solid-state systems. This article
reviews the current status of this subject, including both recent advances and
well-established results. The primary focus is on the basic physical principles
underlying the generation of carrier spin polarization, spin dynamics, and
spin-polarized transport in semiconductors and metals. Spin transport differs
from charge transport in that spin is a nonconserved quantity in solids due to
spin-orbit and hyperfine coupling. The authors discuss in detail spin
decoherence mechanisms in metals and semiconductors. Various theories of spin
injection and spin-polarized transport are applied to hybrid structures
relevant to spin-based devices and fundamental studies of materials properties.
Experimental work is reviewed with the emphasis on projected applications, in
which external electric and magnetic fields and illumination by light will be
used to control spin and charge dynamics to create new functionalities not
feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes
from the published versio
Social Security, Benefit Claiming and Labor Force Participation: A Quantitative General Equilibrium Approach
Bedmap2: improved ice bed, surface and thickness datasets for Antarctica
We present Bedmap2, a new suite of gridded
products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 S. We derived these products using data from a variety of sources, including many substantial surveys completed
since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made
from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica
the subglacial landscape is visible in much greater detail than was previously available and the improved datacoverage has in many areas revealed the full scale of mountain
ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice
contained in the Antarctic ice sheet (27 million km3) and its potential contribution to sea-level rise (58 m) are similar
to those of Bedmap1, but the mean thickness of the ice sheet is 4.6% greater, the mean depth of the bed beneath the grounded ice sheet is 72m lower and the area of ice
sheet grounded on bed below sea level is increased by 10 %.
The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower
than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets
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