137 research outputs found
Skew group algebras, invariants and Weyl Algebras
The aim of this paper is two fold:
First to study finite groups of automorphisms of the homogenized Weyl
algebra , the skew group algebra , the ring of invariants
, and the relations of these algebras with the Weyl algebra ,
with the skew group algebra , and with the ring of invariants
. Of particular interest is the case .
In the on the other hand, we consider the invariant ring \QTR{sl}{C}[X]^{G}
of the polynomial ring in generators, where is a finite subgroup
of Gl(n,\QTR{sl}{C}) such that any element in different from the identity
does not have one as an eigenvalue. We study the relations between the category
of finitely generated modules over \QTR{sl}{C}[X]^{G} and the corresponding
category over the skew group algebra \QTR{sl}{C}% [X]\ast G. We obtain a
generalization of known results for and a finite subgroup of
. In the last part of the paper we extend the results for the
polynomial algebra to the homogenized Weyl algebra
Searching for MHz gravitational waves from harmonic sources
A MHz gravitational wave search for harmonic sources was conducted using a 704 h dataset obtained from the Holometer, a pair of 40 m power recycled Michelson interferometers. Our search was designed to look for cosmic string loops and eccentric black hole binaries in an entirely unexplored frequency range from 1 to 25 MHz. The measured cross-spectral density between both interferometers was used to perform four different searches. First, we search to identify any fundamental frequencies bins that have excess power above 5Ď. Second, we reduce the per-bin threshold on any individual frequency bin by employing that a fundamental frequency and its harmonics all collectively lie above a threshold. We vary the number of harmonics searched over from n = 4 up to n = 23. Third, we perform an agnostic approach to identify harmonic candidates that may have a single contaminated frequency bin or follow a power-law dependence. Lastly, we expand on the agnostic approach for individual candidates and search for a potential underlying population of harmonic sources. Each method was tested on the interferometer dataset, as well as a dark noise, photon shot-noise-limited, and simulated Gaussian-noise datasets. We conclude that these four different search methods did not find any candidate frequencies that would be consistent with harmonic sources. This work presents a new way of searching for gravitational wave candidates, which allowed us to survey a previously unexplored frequency range
Advances in mapping ice-free surfaces within the Northern Antarctic peninsula region using polarimetric RADARSAT-2 data
Ice-free areas within the Northern Antarctic Peninsula
region are of interest for studying changes occurring to
surface covers, including those related to glacial coverage,
raised beach deposits and periglacial processes and
permafrost. The objective of this work is to map the main
surface covers within ice-free areas of King George Island,
the largest island of the South Shetlands archipelago, using
fully polarimetric RADARSAT-2 SAR data.
Surface covers such as rock outcrops and glacial till, stone
fields, patterned ground, and sand and gravel deposits form
the most representative classes and account for 84 km2 of
the ice-free areas on the island. A distribution of complex
geomorphological features and landforms was obtained,
being some of them considered indicators of periglacial
processes and presence of permafrost.Published versio
Searching for MHz gravitational waves from harmonic sources
A MHz gravitational wave search for harmonic sources was conducted using a 704 h dataset obtained from the Holometer, a pair of 40 m power recycled Michelson interferometers. Our search was designed to look for cosmic string loops and eccentric black hole binaries in an entirely unexplored frequency range from 1 to 25 MHz. The measured cross-spectral density between both interferometers was used to perform four different searches. First, we search to identify any fundamental frequencies bins that have excess power above 5Ď. Second, we reduce the per-bin threshold on any individual frequency bin by employing that a fundamental frequency and its harmonics all collectively lie above a threshold. We vary the number of harmonics searched over from n = 4 up to n = 23. Third, we perform an agnostic approach to identify harmonic candidates that may have a single contaminated frequency bin or follow a power-law dependence. Lastly, we expand on the agnostic approach for individual candidates and search for a potential underlying population of harmonic sources. Each method was tested on the interferometer dataset, as well as a dark noise, photon shot-noise-limited, and simulated Gaussian-noise datasets. We conclude that these four different search methods did not find any candidate frequencies that would be consistent with harmonic sources. This work presents a new way of searching for gravitational wave candidates, which allowed us to survey a previously unexplored frequency range
Flat-band localization and interaction-induced delocalization of photons
Advances in quantum engineering have enabled the design, measurement, and
precise control of synthetic condensed matter systems. The platform of
superconducting circuits offers two particular capabilities: flexible
connectivity of circuit elements that enables a variety of lattice geometries,
and circuit nonlinearity that provides access to strongly interacting physics.
Separately, these features have allowed for the creation of curved-space
lattices and the realization of strongly correlated phases and dynamics in
one-dimensional chains and square lattices. Missing in this suite of
simulations is the simultaneous integration of interacting particles into
lattices with unique band dispersions, such as dispersionless flat bands. An
ideal building block for flat-band physics is the Aharonov-Bohm cage: a single
plaquette of a lattice whose band structure consists entirely of flat bands.
Here, we experimentally construct an Aharonov-Bohm cage and observe the
localization of a single photon, the hallmark of all-bands-flat physics. Upon
placing an interaction-bound photon pair into the cage, we see a delocalized
walk indicating an escape from Aharonov-Bohm caging. We further find that a
variation of caging persists for two particles initialized on opposite sites of
the cage. These results mark the first experimental observation of a quantum
walk that becomes delocalized due to interactions and establish superconducting
circuits for studies of flat-band-lattice dynamics with strong interactions.Comment: 8 + 9 pages, 4 + 12 figures, 0 + 2 tables; modified title, added a
supplementary figure, and modified the definition used for tunneling tim
Zinc oxide nanowires-based flexible pressure sensor
Abstract Embedding piezoelectric nanowires within a soft elastomer material should provide a superior pressure sensing transducer, exploiting the piezoelectric properties of the nanowire material while maintaining flexibility. Here, a flexible sensor has been fabricated on a Kapton substrate and has incorporated a layer of polydimethylsiloxane with embedded zinc oxide nanowires as the pressure sensing mechanism. In response to applied compressive pressure up to 127Â kPa, the device has generated a voltage, between electrodes on either side of the nanowire/polydimethylsiloxane layer, with a sensitivity of 23.6Â mV/kPa, which is 100 times greater than previously reported zinc oxide nanostructureâbased flexible sensors
SEOM-GEIS clinical guideline for gastrointestinal stromal tumors (2022)
Avapritinib; Imatinib; RipretinibAvapritinib; Imatinib; RipretinibAvapritinib; Imatinib; RipretinibGastrointestinal stromal tumor (GIST) is the most common malignant neoplasm of mesenchymal origin, and a paradigmatic model for a successful rational development of targeted therapies in cancer. The introduction of tyrosine kinase inhibitors with activity against KIT/PDGFRA in both localized and advanced stages has remarkably improved the survival in a disease formerly deemed resistant to all systemic therapies. These guidelines are elaborated by the conjoint effort of the Spanish Society of Medical Oncology (SEOM) and the Spanish Sarcoma Research Group (GEIS) and provide a multidisciplinary and updated consensus for the diagnosis and treatment of GIST patients. We strongly encourage that the managing of these patients should be performed within multidisciplinary teams in reference centers
- âŚ