839 research outputs found
Asymptotic Approximations for TCP Compound
In this paper, we derive an approximation for throughput of TCP Compound
connections under random losses. Throughput expressions for TCP Compound under
a deterministic loss model exist in the literature. These are obtained assuming
the window sizes are continuous, i.e., a fluid behaviour is assumed. We
validate this model theoretically. We show that under the deterministic loss
model, the TCP window evolution for TCP Compound is periodic and is independent
of the initial window size. We then consider the case when packets are lost
randomly and independently of each other. We discuss Markov chain models to
analyze performance of TCP in this scenario. We use insights from the
deterministic loss model to get an appropriate scaling for the window size
process and show that these scaled processes, indexed by p, the packet error
rate, converge to a limit Markov chain process as p goes to 0. We show the
existence and uniqueness of the stationary distribution for this limit process.
Using the stationary distribution for the limit process, we obtain
approximations for throughput, under random losses, for TCP Compound when
packet error rates are small. We compare our results with ns2 simulations which
show a good match.Comment: Longer version for NCC 201
Analysis of Multiple Flows using Different High Speed TCP protocols on a General Network
We develop analytical tools for performance analysis of multiple TCP flows
(which could be using TCP CUBIC, TCP Compound, TCP New Reno) passing through a
multi-hop network. We first compute average window size for a single TCP
connection (using CUBIC or Compound TCP) under random losses. We then consider
two techniques to compute steady state throughput for different TCP flows in a
multi-hop network. In the first technique, we approximate the queues as M/G/1
queues. In the second technique, we use an optimization program whose solution
approximates the steady state throughput of the different flows. Our results
match well with ns2 simulations.Comment: Submitted to Performance Evaluatio
On Asymptotic Symmetries of 3d Extended Supergravities
We study asymptotic symmetry algebras for classes of three dimensional
supergravities with and without cosmological constant. In the first part we
generalise some of the non-Dirichlet boundary conditions of gravity to
extended supergravity theories, and compute their asymptotic symmetries. In
particular, we show that the boundary conditions proposed to holographically
describe the chiral induced gravity and Liouville gravity do admit extension to
the supergravity contexts with appropriate superalgebras as their asymptotic
symmetry algebras. In the second part we consider generalisation of the 3d
computation to extended supergravities without cosmological constant, and
show that their asymptotic symmetry algebras provide examples of nonlinear
extended superalgebras containing the algebra
Holographic chiral induced W-gravities
We study boundary conditions for 3-dimensional higher spin gravity that admit
asymptotic symmetry algebras expected of 2-dimensional induced higher spin
theories in the light cone gauge. For the higher spin theory based on sl(3, R)
plus sl(3,R) algebra, our boundary conditions give rise to one copy of
classical W3 and a copy of sl(3,R) or su(1,2) Kac-Moody symmetry algebra. We
propose that the higher spin theories with these boundary conditions describe
appropriate chiral induced W-gravity theories on the boundary. We also consider
boundary conditions of spin-3 higher spin gravity that admit u(1) plus u(1)
current algebra.Comment: 19 page
Species Classification using DNA Barcoding and Profile Hidden Markov Models
Traditional classification systems for living organisms like the Linnaean taxonomy involved classification based on morphological features of species. This traditional system is being replaced by molecular approaches which involve using gene sequences. The COI gene, also known as the ”DNA barcode” since it is unique in every species, can be used to uniquely identify organisms and thus, classify them. Classifying using gene sequences has many advantages, including correct identification of cryptic species(individuals which appear similar but belong to different species) and species which are extremely small in size. In this project, I worked on classifying COI sequences of unknown species to a genus, using Profile Hidden Markov Models.
(Taxonomy Ranks: Kingdom → Phylum → Class → Order →Family → Genus → Species
An sl(2, R) current algebra from AdS_3 gravity
We provide a set of chiral boundary conditions for three-dimensional gravity
that allow for asymptotic symmetries identical to those of two-dimensional
induced gravity in light-cone gauge considered by Polyakov. These are the most
general boundary conditions consistent with the boundary terms introduced by
Compere, Song and Strominger recently. We show that the asymptotic symmetry
algebra of our boundary conditions is an sl(2,R) current algebra with level
given by c/6. The fully non-linear solution in Fefferman--Graham coordinates is
also provided along with its charges.Comment: 8 page
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