300 research outputs found
Probing the Tavis-Cummings level splitting with intermediate-scale superconducting circuits
We demonstrate the local control of up to eight two-level systems interacting
strongly with a microwave cavity. Following calibration, the frequency of each
individual two-level system (qubit) is tunable without influencing the others.
Bringing the qubits one by one on resonance with the cavity, we observe the
collective coupling strength of the qubit ensemble. The splitting scales up
with the square root of the number of the qubits, which is the hallmark of the
Tavis-Cummings model. The local control circuitry causes a bypass shunting the
resonator, and a Fano interference in the microwave readout, whose contribution
can be calibrated away to recover the pure cavity spectrum. The simulator's
attainable size of dressed states with up to five qubits is limited by reduced
signal visibility, and -- if uncalibrated -- by off-resonance shifts of
sub-components. Our work demonstrates control and readout of quantum coherent
mesoscopic multi-qubit system of intermediate scale under conditions of noise
Blind Curvelet based Denoising of Seismic Surveys in Coherent and Incoherent Noise Environments
The localized nature of curvelet functions, together with their frequency and
dip characteristics, makes the curvelet transform an excellent choice for
processing seismic data. In this work, a denoising method is proposed based on
a combination of the curvelet transform and a whitening filter along with
procedure for noise variance estimation. The whitening filter is added to get
the best performance of the curvelet transform under coherent and incoherent
correlated noise cases, and furthermore, it simplifies the noise estimation
method and makes it easy to use the standard threshold methodology without
digging into the curvelet domain. The proposed method is tested on
pseudo-synthetic data by adding noise to real noise-less data set of the
Netherlands offshore F3 block and on the field data set from east Texas, USA,
containing ground roll noise. Our experimental results show that the proposed
algorithm can achieve the best results under all types of noises (incoherent or
uncorrelated or random, and coherent noise)
Lectures on the functional renormalization group method
These introductory notes are about functional renormalization group equations
and some of their applications. It is emphasised that the applicability of this
method extends well beyond critical systems, it actually provides us a general
purpose algorithm to solve strongly coupled quantum field theories. The
renormalization group equation of F. Wegner and A. Houghton is shown to resum
the loop-expansion. Another version, due to J. Polchinski, is obtained by the
method of collective coordinates and can be used for the resummation of the
perturbation series. The genuinely non-perturbative evolution equation is
obtained in a manner reminiscent of the Schwinger-Dyson equations. Two variants
of this scheme are presented where the scale which determines the order of the
successive elimination of the modes is extracted from external and internal
spaces. The renormalization of composite operators is discussed briefly as an
alternative way to arrive at the renormalization group equation. The scaling
laws and fixed points are considered from local and global points of view.
Instability induced renormalization and new scaling laws are shown to occur in
the symmetry broken phase of the scalar theory. The flattening of the effective
potential of a compact variable is demonstrated in case of the sine-Gordon
model. Finally, a manifestly gauge invariant evolution equation is given for
QED.Comment: 47 pages, 11 figures, final versio
Variational calculations with improved energy functionals in gauge theories
For a SU(N) Yang-Mills theory, we present variational calculations using
gaussian wave functionals combined with an approximate projection on gauge
invariant states. The projection amounts to correcting the energy of the
gaussian states by substracting the spurious energy associated with gauge
rotations. Based on this improved energy functional, we perform variational
calculations of the interaction energy in the presence of external electric and
magnetic fields. We verify that the ultraviolet behaviour of our approximation
scheme is consistent, as it should, with that expected from perturbation
theory. In particular, we recover in this variational framework the standard
one-loop beta function, with a transparent interpretation of the screening and
anti-screening contributions.Comment: 40 pages, no figure
Strings on conifolds from strong coupling dynamics: quantitative results
Three quantitative features of string theory on AdS_5 x X_5, for any
(quasi)regular Sasaki-Einstein X_5, are recovered exactly from an expansion of
field theory at strong coupling around configurations in the moduli space of
vacua. These configurations can be thought of as a generalized matrix model of
(local) commuting matrices. First, we reproduce the spectrum of scalar
Kaluza-Klein modes on X_5. Secondly, we recover the precise spectrum of BMN
string states, including a nontrivial dependence on the volume of X_5. Finally,
we show how the radial direction in global AdS_5 emerges universally in these
theories by exhibiting states dual to AdS giant gravitons.Comment: 1+28 pages. 1 figur
On Casimir Pistons
In this paper we study the Casimir force for a piston configuration in
with one dimension being slightly curved and the other two infinite. We work
for two different cases with this setup. In the first, the piston is "free to
move" along a transverse dimension to the curved one and in the other case the
piston "moves" along the curved one. We find that the Casimir force has
opposite signs in the two cases. We also use a semi-analytic method to study
the Casimir energy and force. In addition we discuss some topics for the
aforementioned piston configuration in and for possible modifications
from extra dimensional manifolds.Comment: 20 pages, To be published in MPL
Pi N sigma-term and chiral-odd twist-3 distribution function e(x) of the nucleon in the chiral quark soliton model
The isosinglet combination of the chiral-odd twist-3 distribution function
of the nucleon has outstanding properties that its first moment
is proportional to the well-known sigma-term and that it contains a
-function singularity at . These two features are inseparably
connected in that the above sum rule would be violated, if there is no such a
singularity in . Very recently, we found that the physical
origin of this -function singularity can be traced back to the
long-range quark-quark correlation of scalar type, which signals the
spontaneous chiral symmetry breaking of the QCD vacuum. The main purpose of the
present paper is to give complete theoretical predictions for the chiral-odd
twist-3 distribution function of each flavor on the basis of the
chiral quark soliton model, without recourse to the derivative expansion type
approximation. These theoretical predictions are then compared with the
empirical information extracted from the CLAS data of the semi-inclusive DIS
processes by assuming the Collins mechanism only. A good agreement with the
CLAS data is indicative of a sizable violation of the sigma-term sum
rule, or equivalently, the existence of a -function singularity in
.Comment: 35 pages, 10 figure
DETECTION OF UNFOCUSED RAINDROPS ON CAR WINDSCREEN COMPARATIVE ANALYSIS USING BACKGROUND SUBRACTIONAND AND WATERSHED ALGORTIHM
Use of ADAS in top end cars has been prevalent over past decade. Electronic control and assistance in cars has proven to be a major feature resulting in passenger safety, saving lives as well as preventing fatalities. This system can be trusted or counted upon in clear weather conditions, which by now has been the only limitation questioning the usefulness of ADAS. Current research focuses to strengthen ADAS in rainy climatic conditions. This paper puts forth a novel idea to detect raindrops where ADAS can be used to increase its functionality in rainy condition to control the speed of over-speeding cars. The method basically includes image database on which Background Subtraction and Watershed algorithm are run to find out a numerical data, and to measure performance of both the method. This data can be used to improve ADAS performance in rainy conditions
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