560 research outputs found
D-branes in Unoriented Non-critical Strings and Duality in SO(N) and Sp(N) Gauge Theories
We exhibit exact conformal field theory descriptions of SO(N) and Sp(N) pairs
of Seiberg-dual gauge theories within string theory. The N=1 gauge theories
with flavour are realized as low energy limits of the worldvolume theories on
D-branes in unoriented non-critical superstring backgrounds. These unoriented
backgrounds are obtained by constructing exact crosscap states in the
SL(2,R)/U(1) coset conformal field theory using the modular bootstrap method.
Seiberg duality is understood by studying the behaviour of the boundary and
crosscap states under monodromy in the closed string parameter space.Comment: 23 pages, 2 figure
Topological Cigar and the c=1 String : Open and Closed
We clarify some aspects of the map between the c=1 string theory at self-dual
radius and the topologically twisted cigar at level one. We map the ZZ and FZZT
D-branes in the c=1 string theory at self dual radius to the localized and
extended branes in the topological theory on the cigar. We show that the open
string spectrum on the branes in the two theories are in correspondence with
each other, and their two point correlators are equal. We also find a
representation of an extended N=2 algebra on the worldsheet which incorporates
higher spin currents in terms of asymptotic variables on the cigar.Comment: 37 pages, 2 figures, corrections to section 3.1, references adde
The Topological Cigar Observables
We study the topologically twisted cigar, namely the SL(2,R)/U(1)
superconformal field theory at arbitrary level, and find the BRST cohomology of
the topologically twisted N=2 theory. We find a one to one correspondence
between the spectrum of the twisted coset and singular vectors in the Wakimoto
modules constructed over the SL(2,R) current algebra. The topological cigar
cohomology is the crucial ingredient in calculating the closed string spectrum
of topological strings on non-compact Gepner models.Comment: 28 page
Tree-Level Stability Without Spacetime Fermions: Novel Examples in String Theory
Is perturbative stability intimately tied with the existence of spacetime
fermions in string theory in more than two dimensions? Type 0'B string theory
in ten-dimensional flat space is a rare example of a non-tachyonic,
non-supersymmetric string theory with a purely bosonic closed string spectrum.
However, all known type 0' constructions exhibit massless NSNS tadpoles
signaling the fact that we are not expanding around a true vacuum of the
theory. In this note, we are searching for perturbatively stable examples of
type 0' string theory without massless tadpoles in backgrounds with a spatially
varying dilaton. We present two examples with this property in non-critical
string theories that exhibit four- and six-dimensional Poincare invariance. We
discuss the D-branes that can be embedded in this context and the type of gauge
theories that can be constructed in this manner. We also comment on the
embedding of these non-critical models in critical string theories and their
holographic (Little String Theory) interpretation and propose a general
conjecture for the role of asymptotic supersymmetry in perturbative string
theory.Comment: harvmac, 29 pages; v2 minor changes, version to appear in JHE
In-orbit Performance of UVIT on ASTROSAT
We present the in-orbit performance and the first results from the
ultra-violet Imaging telescope (UVIT) on ASTROSAT. UVIT consists of two
identical 38cm coaligned telescopes, one for the FUV channel (130-180nm) and
the other for the NUV (200-300nm) and VIS (320-550nm) channels, with a field of
view of 28 . The FUV and the NUV detectors are operated in the high
gain photon counting mode whereas the VIS detector is operated in the low gain
integration mode. The FUV and NUV channels have filters and gratings, whereas
the VIS channel has filters. The ASTROSAT was launched on 28th September 2015.
The performance verification of UVIT was carried out after the opening of the
UVIT doors on 30th November 2015, till the end of March 2016 within the
allotted time of 50 days for calibration. All the on-board systems were found
to be working satisfactorily. During the PV phase, the UVIT observed several
calibration sources to characterise the instrument and a few objects to
demonstrate the capability of the UVIT. The resolution of the UVIT was found to
be about 1.4 - 1.7 in the FUV and NUV. The sensitivity in various
filters were calibrated using standard stars (white dwarfs), to estimate the
zero-point magnitudes as well as the flux conversion factor. The gratings were
also calibrated to estimate their resolution as well as effective area. The
sensitivity of the filters were found to be reduced up to 15\% with respect to
the ground calibrations. The sensitivity variation is monitored on a monthly
basis. UVIT is all set to roll out science results with its imaging capability
with good resolution and large field of view, capability to sample the UV
spectral region using different filters and capability to perform variability
studies in the UV.Comment: 10 pages, To appear in SPIE conference proceedings, SPIE conference
paper, 201
Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)
The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the
India-based Neutrino Observatory (INO) is designed to study the atmospheric
neutrinos and antineutrinos separately over a wide range of energies and path
lengths. The primary focus of this experiment is to explore the Earth matter
effects by observing the energy and zenith angle dependence of the atmospheric
neutrinos in the multi-GeV range. This study will be crucial to address some of
the outstanding issues in neutrino oscillation physics, including the
fundamental issue of neutrino mass hierarchy. In this document, we present the
physics potential of the detector as obtained from realistic detector
simulations. We describe the simulation framework, the neutrino interactions in
the detector, and the expected response of the detector to particles traversing
it. The ICAL detector can determine the energy and direction of the muons to a
high precision, and in addition, its sensitivity to multi-GeV hadrons increases
its physics reach substantially. Its charge identification capability, and
hence its ability to distinguish neutrinos from antineutrinos, makes it an
efficient detector for determining the neutrino mass hierarchy. In this report,
we outline the analyses carried out for the determination of neutrino mass
hierarchy and precision measurements of atmospheric neutrino mixing parameters
at ICAL, and give the expected physics reach of the detector with 10 years of
runtime. We also explore the potential of ICAL for probing new physics
scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration,
Contents identical with the version published in Pramana - J. Physic
Semichiral fields on S^2 and generalized Kahler geometry
Abstract: We study a class of two-dimensional N=(2,2) supersymmetric gauge theories, given by semichiral multiplets coupled to the usual vector multiplet. In the UV, these theories are traditional gauge theories deformed by a gauged Wess-Zumino term. In the IR, they give rise to nonlinear sigma models on noncompact generalized K\ue4hler manifolds, which contain a three-form field H and whose metric is not K\ue4hler. We place these theories on S2 and compute their partition function exactly with localization techniques. We find that the contribution of instantons to the partition function that we define is insensitive to the deformation, and discuss our results from the point of view of the generalized K\ue4hler target space. \ua9 2016, The Author(s)
Curation of viral genomes: challenges, applications and the way forward
BACKGROUND: Whole genome sequence data is a step towards generating the 'parts list' of life to understand the underlying principles of Biocomplexity. Genome sequencing initiatives of human and model organisms are targeted efforts towards understanding principles of evolution with an application envisaged to improve human health. These efforts culminated in the development of dedicated resources. Whereas a large number of viral genomes have been sequenced by groups or individuals with an interest to study antigenic variation amongst strains and species. These independent efforts enabled viruses to attain the status of 'best-represented taxa' with the highest number of genomes. However, due to lack of concerted efforts, viral genomic sequences merely remained as entries in the public repositories until recently. RESULTS: VirGen is a curated resource of viral genomes and their analyses. Since its first release, it has grown both in terms of coverage of viral families and development of new modules for annotation and analysis. The current release (2.0) includes data for twenty-five families with broad host range as against eight in the first release. The taxonomic description of viruses in VirGen is in accordance with the ICTV nomenclature. A well-characterised strain is identified as a 'representative entry' for every viral species. This non-redundant dataset is used for subsequent annotation and analyses using sequenced-based Bioinformatics approaches. VirGen archives precomputed data on genome and proteome comparisons. A new data module that provides structures of viral proteins available in PDB has been incorporated recently. One of the unique features of VirGen is predicted conformational and sequential epitopes of known antigenic proteins using in-house developed algorithms, a step towards reverse vaccinology. CONCLUSION: Structured organization of genomic data facilitates use of data mining tools, which provides opportunities for knowledge discovery. One of the approaches to achieve this goal is to carry out functional annotations using comparative genomics. VirGen, a comprehensive viral genome resource that serves as an annotation and analysis pipeline has been developed for the curation of public domain viral genome data . Various steps in the curation and annotation of the genomic data and applications of the value-added derived data are substantiated with case studies
Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world
Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic.
Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality.
Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States.
Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis.
Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection
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