33,978 research outputs found
Interpolating Action for Strings and Membranes - a Study of Symmetries in the Constrained Hamiltonian Approach
A master action for bosonic strings and membranes, interpolating between the
Nambu--Goto and Polyakov formalisms, is discussed. The role of the gauge
symmetries vis-\`{a}-vis reparametrization symmetries of the various actions is
analyzed by a constrained Hamiltonian approach. This analysis reveals the
difference between strings and higher branes, which is essentially tied to a
degree of freedom count. The cosmological term for membranes follows naturally
in this scheme. The conncetion of our aproach with the Arnowitt--Deser--Misner
representation in general relativity is illuminated.Comment: LaTex, 23 pages; discussion on ADM representation included and new
references adde
Wess-Zumino Consistency Condition for Entanglement Entropy
In this brief note, we consider the variation of the entanglement entropy of
a region as the shape of the entangling surface is changed. We show that the
variation satisfies a Wess-Zumino like integrability condition in field
theories which can be consistently coupled to gravity. In this case the
"anomaly" is localized on the entangling surface. The solution of the
integrability condition should give all the nontrivial finite local terms which
can appear in the variation of the entanglement entropy.Comment: 14 pages, presentation improve
On multi-spin classical strings with NS-NS flux
We study multi spin semiclassical strings in
background supported by a mixture of Neveu-Schwarz-Neveu-Schwarz (NS-NS) and
Ramond-Ramond (R-R) fluxes. This `mixed flux' background has been recently
proved to be classically integrable. We start with a particular rigidly
spinning fundamental string in coupled to the NS-NS flux and
classify the possible profiles. We also find out how the scaling relation among
the energy and angular momenta of such a string changes due to presence of
these fluxes. We emphasize on pure NS-NS flux case and discuss the fate of such
solutions in that limit.Comment: 22 pages, 4 figure
Semiclassical Strings in Supergravity PFT
Puff Field Theory (PFT) is an example of a non-local field theory which
arises from a novel embedding of D-branes in Melvin universe. We study several
rotating and pulsating string solutions of the F-string equations of motion in
the supergravity dual of the PFT. Further, we find a PP-wave geometry from this
nonlocal spacetime by applying a Penrose limit and comment on its similarity
with the maximally supersymmetric PP-wave background.Comment: 21 pages, added clarification
A note on oscillating strings in with mixed three-form fluxes
We present a detailed study of the pulsating string solutions in AdS3 x S3
supported by both RR and NS-NS fluxes. This background has recently been proved
to be integrable. We find the dispersion relation between the energy,
oscillation number and other conserved charges when the NS-NS flux turned on is
small. We further discuss the fate of the string solutions in pure RR and NS-NS
cases.Comment: 26 pages, version to appear in JHE
Spiky strings on AdS3 x S3 with NS-NS flux
We study rigidly rotating strings in the background of AdS3 x S3 with
Neveu-Schwarz (NS) fluxes. We find two interesting limiting cases corresponding
to the known giant magnon and the new single spike solution of strings in the
above background and write down the dispersion relations among various
conserved charges. We use proper regularization to find the correct relations
among them. We further study the circular and infinite spiky strings on AdS and
study their properties.Comment: 19 pages, added clarification, typos fixe
Propagating waves in polar coronal holes as seen by SUMER and EIS
To study the dynamics of coronal holes and the role of waves in the
acceleration of the solar wind, spectral observations were performed over polar
coronal hole regions with the SUMER spectrometer on SoHO and the EIS
spectrometer on Hinode. Using these observations, we aim to detect the presence
of propagating waves in the corona and to study their properties. The
observations analysed here consist of SUMER spectra of the Ne VIII 770 A line
(T = 0.6 MK) and EIS slot images in the Fe XII 195 A line (T = 1.3 MK). Using
the wavelet technique, we study line radiance oscillations at different heights
from the limb in the polar coronal hole regions. We detect the presence of long
period oscillations with periods of 10 to 30 min in polar coronal holes. The
oscillations have an amplitude of a few percent in radiance and are not
detectable in line-of-sight velocity. From the time distance maps we find
evidence for propagating velocities from 75 km/s (Ne VIII) to 125 km/s (Fe
XII). These velocities are subsonic and roughly in the same ratio as the
respective sound speeds. We interpret the observed propagating oscillations in
terms of slow magneto-acoustic waves. These waves can be important for the
acceleration of the fast solar wind.Comment: 5 pages, 7 figures Accepted as Astronomy and Astrophysics Lette
Intelligent Word Embeddings of Free-Text Radiology Reports
Radiology reports are a rich resource for advancing deep learning
applications in medicine by leveraging the large volume of data continuously
being updated, integrated, and shared. However, there are significant
challenges as well, largely due to the ambiguity and subtlety of natural
language. We propose a hybrid strategy that combines semantic-dictionary
mapping and word2vec modeling for creating dense vector embeddings of free-text
radiology reports. Our method leverages the benefits of both
semantic-dictionary mapping as well as unsupervised learning. Using the vector
representation, we automatically classify the radiology reports into three
classes denoting confidence in the diagnosis of intracranial hemorrhage by the
interpreting radiologist. We performed experiments with varying hyperparameter
settings of the word embeddings and a range of different classifiers. Best
performance achieved was a weighted precision of 88% and weighted recall of
90%. Our work offers the potential to leverage unstructured electronic health
record data by allowing direct analysis of narrative clinical notes.Comment: AMIA Annual Symposium 201
- …