15,872 research outputs found
Exact Lagrangian submanifolds in simply-connected cotangent bundles
We consider exact Lagrangian submanifolds in cotangent bundles. Under certain
additional restrictions (triviality of the fundamental group of the cotangent
bundle, and of the Maslov class and second Stiefel-Whitney class of the
Lagrangian submanifold) we prove such submanifolds are Floer-cohomologically
indistinguishable from the zero-section. This implies strong restrictions on
their topology. An essentially equivalent result was recently proved
independently by Nadler, using a different approach.Comment: 28 pages, 3 figures. Version 2 -- derivation and discussion of the
spectral sequence considerably expanded. Other minor change
The Electronic States of Two Oppositely doped Mott Insulators Bilayers
We study the effect of Coulomb interaction between two oppositely doped
low-dimensional tJ model systems. We exactly show that, in the one-dimensional
case, an arbitrarily weak interaction leads to the formation of charge neutral
electron-hole pairs. We then use two different mean-field theories to address
the two-dimensional case, where inter-layer excitons also form and condense. We
propose that this results in new features which have no analog in single
layers, such as the emergence of an insulating spin liquid phase. Our simple
bilayer model might have relevance to the physics of doped Mott insulator
interfaces and of the new four layer Ba2CaCu4O8 compound.Comment: 4 pages, 1 figur
Improved Implementation of Point Location in General Two-Dimensional Subdivisions
We present a major revamp of the point-location data structure for general
two-dimensional subdivisions via randomized incremental construction,
implemented in CGAL, the Computational Geometry Algorithms Library. We can now
guarantee that the constructed directed acyclic graph G is of linear size and
provides logarithmic query time. Via the construction of the Voronoi diagram
for a given point set S of size n, this also enables nearest-neighbor queries
in guaranteed O(log n) time. Another major innovation is the support of general
unbounded subdivisions as well as subdivisions of two-dimensional parametric
surfaces such as spheres, tori, cylinders. The implementation is exact,
complete, and general, i.e., it can also handle non-linear subdivisions. Like
the previous version, the data structure supports modifications of the
subdivision, such as insertions and deletions of edges, after the initial
preprocessing. A major challenge is to retain the expected O(n log n)
preprocessing time while providing the above (deterministic) space and
query-time guarantees. We describe an efficient preprocessing algorithm, which
explicitly verifies the length L of the longest query path in O(n log n) time.
However, instead of using L, our implementation is based on the depth D of G.
Although we prove that the worst case ratio of D and L is Theta(n/log n), we
conjecture, based on our experimental results, that this solution achieves
expected O(n log n) preprocessing time.Comment: 21 page
Symmetry Detection in Large Scale City Scans
In this report we present a novel method for detecting partial symmetries in very large point clouds of 3D city scans. Unlike previous work, which was limited to data sets of a few hundred megabytes maximum, our method scales to very large scenes. We map the detection problem to a nearestneighbor search in a low-dimensional feature space, followed by a cascade of tests for geometric clustering of potential matches. Our algorithm robustly handles noisy real-world scanner data, obtaining a recognition performance comparable to state-of-the-art methods. In practice, it scales linearly with the scene size and achieves a high absolute throughput, processing half a terabyte of raw scanner data over night on a dual socket commodity PC
MUSE-AO view of the starburst-AGN connection: NGC 7130
We present the discovery of a small kinematically decoupled core of
0.2 (60 pc) in radius as well as an outflow jet in the
archetypical AGN-starburst "composite" galaxy NGC 7130 from integral field data
obtained with the adaptive optics-assisted MUSE-NFM instrument on the VLT.
Correcting the already good natural seeing at the time of our science
verification observations with the four-laser GALACSI AO system, we reach an
unprecedented spatial resolution at optical wavelengths of around
0.15. We confirm the existence of star-forming knots arranged
in a ring of 0.58 (185 pc) in radius around the nucleus,
previously observed from UV and optical Hubble Space Telescope and CO(6-5) ALMA
imaging. We determine the position of the nucleus as the location of a peak in
gas velocity dispersion. A plume of material extends towards the NE from the
nucleus until at least the edge of our field of view at 2 (640
pc) radius which we interpret as an outflow jet originating in the AGN. The
plume is not visible morphologically, but is clearly characterised in our data
by emission-line ratios characteristic of AGN emission, enhanced gas velocity
dispersion, and distinct non-circular gas velocities. Its orientation is
roughly perpendicular to the line of nodes of the rotating host galaxy disc. A
circumnuclear area of positive and negative velocities of 0.2
in radius indicates a tiny inner disc, which can only be seen after combining
the integral field spectroscopic capabilities of MUSE with adaptive optics.Comment: Accepted for publication in A&A letter
Accumulated environmental risk in young refugees – A prospective evaluation
Background: Recently, we reported a strong, disease-independent relationship between accumulated pre-adult environmental risks and violent aggression later in life. Risk factors were interchangeable, and migration was among the explored risks. Alarmed by these data, we assessed collected risk loadin young ‘healthy’ refugees as a specifics group of current migration streams and evaluated first signals of behavioral abnormalities. Methods: In 9 German refugee centers, n=133 young refugees, not previously in contact with the health system, were recruited, many of them unaccompanied minors. Risk factors experienced apart from migration/refuge were carefully assessed: Traumatic experiences before/during/after flight (including war,genocide, human trafficking, torture, murder, slavery, terrorist attacks), urbanicity, physical and sexual abuse, problematic alcohol and cannabis use (lifetime). Evaluation comprised physical exam and psychopathology screening. Findings: Refugees arrived in Germany via Eastern Mediterranean/Balkanroute (34.6%), from Africa via Central Mediterranean route (39.1%), by plane (17.3%) or other routes, such as Western Mediterranean or Atlantic (9.0%). Flight reasons were war/expulsion (25.6%), persecution/threats to life (51.9%), economical/others (22.5%). Interpretation: refugees from hosting countries with alarming 'risk burden', should be considered as highly vulnerable towards development of global functional deficits, behavioral abnormalities, and neuropsychiatric disorders. Rapid proactive integration or sustainable support of those who will return to rebuild their countries are mandatory
On possible lower bounds for the direct detection rate of SUSY Dark Matter
One can expect accessible lower bounds for dark matter detection rate due to
restrictions on masses of the SUSY-partners. To explore this correlation one
needs a new-generation large-mass detector. The absolute lower bound for
detection rate can naturally be due to spin-dependent interaction. Aimed at
detecting dark matter with sensitivity higher than event/day/kg an
experiment should have a non-zero-spin target. Perhaps, the best is to create a
GENIUS-like detector with both Ge-73 (high spin) and Ge-76 nuclei.Comment: latex, 5 pages, 3 figures. Talk given at the III International
Conference on Non-accelerator New Physics (NANP'01), Dubna, 19--23 June, 200
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