29 research outputs found
Finite Temperature Corrections to Tachyon Mass in Intersecting D-Branes
We continue with the analysis of finite temperature corrections to the
Tachyon mass in intersecting branes which was initiated in arxiv:1403.0389. In
this paper we extend the computation to the case of intersecting D3-branes by
considering a setup of two intersecting branes in flat-space background. A
holographic model dual to BCS superconductor consisting of intersecting
D8-branes in D4-brane background was proposed in arxiv:1104.2843. The
background considered here is a simplified configuration of this dual model. We
compute the one-loop Tachyon amplitude in the Yang-Mills approximation and show
that the result is finite. Analyzing the amplitudes further we numerically
compute the transition temperature at which the Tachyon becomes massless. The
analytic expressions for the one-loop amplitudes obtained here reduce to those
for intersecting D1-branes obtained in arxiv:1403.0389 as well as those for
intersecting D2-branes.Comment: 73 pages, 24 figures, articl
BCS Instability and Finite Temperature Corrections to Tachyon Mass in Intersecting D1-Branes
A holographic description of BCS superconductivity is given in
arxiv:1104.2843. This model was constructed by insertion of a pair of D8-branes
on a D4-background. The spectrum of intersecting D8-branes has tachyonic modes
indicating an instability which is identified with the BCS instability in
superconductors. Our aim is to study the stability of the intersecting branes
under finite temperature effects. Many of the technical aspects of this problem
are captured by a simpler problem of two intersecting D1-branes on flat
background. In the simplified set-up we compute the one-loop finite temperature
corrections to the tree-level tachyon mass using the frame-work of SU(2)
Yang-Mills theory in (1 + 1)-dimensions. We show that the one-loop two-point
functions are ultraviolet finite due to cancellation of ultraviolet divergence
between the amplitudes containing bosons and fermions in the loop. The
amplitudes are found to be infrared divergent due to the presence of massless
fields in the loops. We compute the finite temperature mass correction to all
the massless fields and use these temperature dependent masses to compute the
tachyonic mass correction. We show numerically the existence of a transition
temperature at which the effective mass of the tree-level tachyons becomes
zero, thereby stabilizing the brane configuration.Comment: Article, 95 pages, 59 figures, improved numerics, added reference
Closed string exchanges on in a background B-field
In an earlier work it was shown that the IR singularities arising in the
nonplanar one loop two point function of a noncommutative gauge
theory can be reproduced exactly from the massless closed string exchanges. The
noncommutative gauge theory is realised on a fractional brane localised
at the fixed point of the orbifold. In this paper we identify the
contributions from each of the closed string modes. The sum of these adds upto
the nonplanar two-point function.Comment: 27 page
A Deep Learning Approach to Detect Lean Blowout in Combustion Systems
Lean combustion is environment friendly with low NOx emissions and also
provides better fuel efficiency in a combustion system. However, approaching
towards lean combustion can make engines more susceptible to lean blowout. Lean
blowout (LBO) is an undesirable phenomenon that can cause sudden flame
extinction leading to sudden loss of power. During the design stage, it is
quite challenging for the scientists to accurately determine the optimal
operating limits to avoid sudden LBO occurrence. Therefore, it is crucial to
develop accurate and computationally tractable frameworks for online LBO
detection in low NOx emission engines. To the best of our knowledge, for the
first time, we propose a deep learning approach to detect lean blowout in
combustion systems. In this work, we utilize a laboratory-scale combustor to
collect data for different protocols. We start far from LBO for each protocol
and gradually move towards the LBO regime, capturing a quasi-static time series
dataset at each condition. Using one of the protocols in our dataset as the
reference protocol and with conditions annotated by domain experts, we find a
transition state metric for our trained deep learning model to detect LBO in
the other test protocols. We find that our proposed approach is more accurate
and computationally faster than other baseline models to detect the transitions
to LBO. Therefore, we recommend this method for real-time performance
monitoring in lean combustion engines
A Comparative Note on Tunneling in AdS and in its Boundary Matrix Dual
For charged black hole, within the grand canonical ensemble, the decay rate
from thermal AdS to the black hole at a fixed high temperature increases with
the chemical potential. We check that this feature is well captured by a
phenomenological matrix model expected to describe its strongly coupled dual.
This comparison is made by explicitly constructing the kink and bounce
solutions around the de-confinement transition and evaluating the matrix model
effective potential on the solutions.Comment: 1+12 pages, 9 figure
Phase transitions in higher derivative gravity and gauge theory: R-charged black holes
This is a continuation of our earlier work where we constructed a
phenomenologically motivated effective action of the boundary gauge theory at
finite temperature and finite gauge coupling on . In this
paper, we argue that this effective action qualitatively reproduces the gauge
theory representing various bulk phases of R-charged black hole with
Gauss-Bonnet correction. We analyze the system both in canonical and grand
canonical ensemble.Comment: 36 pages, 16 figures; v2: typos corrected, references adde
Aspects of Open-Closed Duality in a Background B-Field II
It was shown in [hep-th/0503009], in the context of bosonic theory that the
IR singular terms that arise as a result of integrating out high momentum modes
in nonplanar diagrams of noncommutative gauge theory can be recovered from low
lying tree-level closed string exchanges. This follows as a natural consequence
of world-sheet open-closed string duality. Here using the same setup we study
the phenomenon for noncommutative gauge theory realised on a
fractional brane localised at the fixed point of . The IR
singularities from the massless closed string exchanges are exactly equal to
those coming from one-loop gauge theory. This is as a result of cancellation of
all contributions from the massive modes.Comment: 27 pages, 1 figure, references added, typos correcte
A note on matrix model with IR cutoff and AdS/CFT
We propose an effective model of strongly coupled gauge theory at finite
temperature on in the presence of an infrared cutoff. It is constructed
by considering the theory on with an infrared cutoff and then taking the
size of the to infinity while keeping the cutoff fixed. This model
reproduces various qualitative features expected from its gravity dual.Comment: 27 pages, 9 figures, an appendix added, other minor changes, journal
versio
Phase Transitions in Higher Derivative Gravity
This paper deals with black holes, bubbles and orbifolds in Gauss-Bonnet
theory in five dimensional anti de Sitter space. In particular, we study
stable, unstable and metastable phases of black holes from thermodynamical
perspective. By comparing bubble and orbifold geometries, we analyse associated
instabilities. Assuming AdS/CFT correspondence, we discuss the effects of this
higher derivative bulk coupling on a specific matrix model near the critical
points of the boundary gauge theory at finite temperature. Finally, we propose
another phenomenological model on the boundary which mimics various phases of
the bulk space-time.Comment: 33 pages, 12 figures, LaTeX, typos corrected, clarifications in
sections 5 and 6, references adde
On the UV renormalizability of noncommutative field theories
UV/IR mixing is one of the most important features of noncommutative field
theories. As a consequence of this coupling of the UV and IR sectors, the
configuration of fields at the zero momentum limit in these theories is a very
singular configuration. We show that the renormalization conditions set at a
particular momentum configuration with a fixed number of zero momenta,
renormalizes the Green's functions for any general momenta only when this
configuration has same set of zero momenta. Therefore only when renormalization
conditions are set at a point where all the external momenta are nonzero, the
quantum theory is renormalizable for all values of nonzero momentum. This
arises as a result of different scaling behaviors of Green's functions with
respect to the UV cutoff () for configurations containing different
set of zero momenta. We study this in the noncommutative theory and
analyse similar results for the Gross-Neveu model at one loop level. We next
show this general feature using Wilsonian RG of Polchinski in the globally O(N)
symmetric scalar theory and prove the renormalizability of the theory to all
orders with an infrared cutoff. In the context of spontaneous symmetry breaking
(SSB) in noncommutative scalar theory, it is essential to note the different
scaling behaviors of Green's functions with respect to for different
set of zero momenta configurations. We show that in the broken phase of the
theory the Ward identities are satisfied to all orders only when one keeps an
infrared regulator by shifting to a nonconstant vacuum.Comment: 29 pages, 8 figures, uses JHEP.cls, references adde