481 research outputs found
Wilson Loops in N=2 Super-Yang-Mills from Matrix Model
We compute the expectation value of the circular Wilson loop in N=2
supersymmetric Yang-Mills theory with N_f=2N hypermultiplets. Our results
indicate that the string tension in the dual string theory scales as the
logarithm of the 't Hooft coupling.Comment: 37 pages, 9 figures; v2: Numerical factors corrected, simple
derivation of Wilson loop and discussion of continuation to complex lambda
added; v3: instanton partition function re-analyzed in order to take into
account a contribution of the hypermultiplet
A note on perturbation series in supersymmetric gauge theories
Exact results in supersymmetric Chern-Simons and N=2 Yang-Mills theories can
be used to examine the quantum behavior of observables and the structure of the
perturbative series. For the U(2) x U(2) ABJM model, we determine the
asymptotic behavior of the perturbative series for the partition function and
write it as a Borel transform. Similar results are obtained for N=2 SU(2) super
Yang-Mills theory with four fundamental flavors and in N=2* super Yang-Mills
theory, for the partition function as well as for the expectation values for
Wilson loop and 't Hooft loop operators (in the 0 and 1 instanton sectors). In
all examples, one has an alternate perturbation series where the coefficient of
the nth term increases as n!, and the perturbation series are Borel summable.
We also calculate the expectation value for a Wilson loop operator in the N=2*
SU(N) theory at large N in different regimes of the 't Hooft gauge coupling and
mass parameter. For large masses, the calculation reproduces the running gauge
coupling for the pure N=2 SYM theory.Comment: 28 pages. V2: minor additions and reference adde
Higher derivative type II string effective actions, automorphic forms and E11
By dimensionally reducing the ten-dimensional higher derivative type IIA
string theory effective action we place constraints on the automorphic forms
that appear in the effective action in lower dimensions. We propose a number of
properties of such automorphic forms and consider the prospects that E11 can
play a role in the formulation of the higher derivative string theory effective
action.Comment: 34 page
Nanoinformatics: developing new computing applications for nanomedicine
Nanoinformatics has recently emerged to address the need of computing applications at the nano level. In this regard, the authors have participated in various initiatives to identify its concepts, foundations and challenges. While nanomaterials open up the possibility for developing new devices in many industrial and scientific areas, they also offer breakthrough perspectives for the prevention, diagnosis and treatment of diseases. In this paper, we analyze the different aspects of nanoinformatics and suggest five research topics to help catalyze new research and development in the area, particularly focused on nanomedicine. We also encompass the use of informatics to further the biological and clinical applications of basic research in nanoscience and nanotechnology, and the related concept of an extended ?nanotype? to coalesce information related to nanoparticles. We suggest how nanoinformatics could accelerate developments in nanomedicine, similarly to what happened with the Human Genome and other -omics projects, on issues like exchanging modeling and simulation methods and tools, linking toxicity information to clinical and personal databases or developing new approaches for scientific ontologies, among many others
An Improved High Order Finite Difference Method for Non-conforming Grid Interfaces for the Wave Equation
This paper presents an extension of a recently developed high order finite difference method for the wave equation on a grid with non-conforming interfaces. The stability proof of the existing methods relies on the interpolation operators being norm-contracting, which is satisfied by the second and fourth order operators, but not by the sixth order operator. We construct new penalty terms to impose interface conditions such that the stability proof does not require the norm-contracting condition. As a consequence, the sixth order accurate scheme is also provably stable. Numerical experiments demonstrate the improved stability and accuracy property
Logarithmic Corrections to Extremal Black Hole Entropy from Quantum Entropy Function
We evaluate the one loop determinant of matter multiplet fields of N=4
supergravity in the near horizon geometry of quarter BPS black holes, and use
it to calculate logarithmic corrections to the entropy of these black holes
using the quantum entropy function formalism. We show that even though
individual fields give non-vanishing logarithmic contribution to the entropy,
the net contribution from all the fields in the matter multiplet vanishes. Thus
logarithmic corrections to the entropy of quarter BPS black holes, if present,
must be independent of the number of matter multiplet fields in the theory.
This is consistent with the microscopic results. During our analysis we also
determine the complete spectrum of small fluctuations of matter multiplet
fields in the near horizon geometry.Comment: LaTeX file, 52 pages; v2: minor corrections, references adde
Photon and polariton fluctuations in arrays of QED-cavities
We propose to detect the Mott insulator-superfluid quantum phase transition
in an array of coupled cavities by studying the polariton and photon
fluctuations in a block of linear dimension M (in units of the lattice constant
of the array). We explicitly show this for a one-dimensional array; the
analysis can be however extended to higher dimensions. In the Mott phase
polariton fluctuations are independent of the block size. In the superfluid
phase they grow logarithmically with M, the prefactor being related to the
compressibility of the system. In the case of photon fluctuations, the critical
behaviour is encoded in the subleading scaling with the block dimension, while
the leading behaviour is linear in M and non-critical. Our results have been
obtained by means of the density matrix renormalization group numerical
algorithm.Comment: 6 pages, 7 figure
Competing mortality in patients diagnosed with bladder cancer: evidence of undertreatment in the elderly and female patients
Background: Bladder cancer (BC) predominantly affects the elderly and is often the cause of death among patients with muscleinvasive disease. Clinicians lack quantitative estimates of competing mortality risks when considering treatments for BC. Our aim was to determine the bladder cancer-specific mortality (CSM) rate and other-cause mortality (OCM) rate for patients with newly diagnosed BC.
Methods: Patients (n Œ 3281) identified from a population-based cancer registry diagnosed between 1994 and 2009. Median
follow-up was 48.15 months (IQ range 18.1â98.7). Competing risk analysis was performed within patient groups and outcomes compared using Grayâs test.
Results: At 5 years after diagnosis, 1246 (40%) patients were dead: 617 (19%) from BC and 629 (19%) from other causes. The 5-year BC mortality rate varied between 1 and 59%, and OCM rate between 6 and 90%, depending primarily on the tumour type and patient age. Cancer-specific mortality was highest in the oldest patient groups. Few elderly patients received radical treatment for invasive cancer (52% vs 12% for patients o60 vs 480 years, respectively). Female patients with high-risk non-muscle-invasive BC had worse CSM than equivalent males (Grayâs Po0.01).
Conclusion: Bladder CSM is highest among the elderly. Female patients with high-risk tumours are more likely to die of their
disease compared with male patients. Clinicians should consider offering more aggressive treatment interventions among older
patients
Strong interface-induced spin-orbit coupling in graphene on WS2
Interfacial interactions allow the electronic properties of graphene to be
modified, as recently demonstrated by the appearance of satellite Dirac cones
in the band structure of graphene on hexagonal boron nitride (hBN) substrates.
Ongoing research strives to explore interfacial interactions in a broader class
of materials in order to engineer targeted electronic properties. Here we show
that at an interface with a tungsten disulfide (WS2) substrate, the strength of
the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The
induced SOI leads to a pronounced low-temperature weak anti-localization (WAL)
effect, from which we determine the spin-relaxation time. We find that
spin-relaxation time in graphene is two-to-three orders of magnitude smaller on
WS2 than on SiO2 or hBN, and that it is comparable to the intervalley
scattering time. To interpret our findings we have performed first-principle
electronic structure calculations, which both confirm that carriers in
graphene-on-WS2 experience a strong SOI and allow us to extract a
spin-dependent low-energy effective Hamiltonian. Our analysis further shows
that the use of WS2 substrates opens a possible new route to access topological
states of matter in graphene-based systems.Comment: Originally submitted version in compliance with editorial guidelines.
Final version with expanded discussion of the relation between theory and
experiments to be published in Nature Communication
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