9,244 research outputs found
K\"ahler Potential of Moduli Space of Calabi-Yau -fold embedded in
We study a kaehler potential K of a one parameter family of Calabi-Yau d-fold
embedded in CP^{d+1}. By comparing results of the topological B-model and the
data of the CFT calculation at Gepner point, the K is determined unambiguously.
It has a moduli parameter psi that describes a deformation of the CFT by a
marginal operator. Also the metric, curvature and hermitian two-point functions
in the neighborhood of the Gepner point are analyzed. We use a recipe of tt^{*}
fusion and develop a method to determine the K from the point of view of
topological sigma model. It is not restricted to this specific model and can be
applied to other Calabi-Yau cases.Comment: 10 pages, 2 figure
Linear shear flow past a hemispherical droplet adhering to a solid surface
This paper investigates the properties of a three dimensional shear flow
overpassing a hemispherical droplet resting on a plane wall. The exact solution
is computed as a function of the viscosity ratio between the droplet and the
surrounding fluid and generalizes the solution for the hemispherical no-slip
bump given in an earlier paper by Price (1985). Several expressions including
the torque and the force acting on the drop will be considered as well as the
importance of the deformations on the surface for small Capillary numbers.Comment: 10 figures, Accepted for publication in Journal of Engineering
Mathematic
Mirror Symmetry of Calabi-Yau Manifolds and Flat Coordinates
We study mirror symmetry of Calabi-Yau manifolds within the framework of the
Gauss-Manin system. Applying the flat coordinates to the Gauss-Manin system for
the periods, we derive differential equations for the mirror map in addition to
the ordinary Picard-Fuchs equations for the periods. These equations are
obtained for a class of one-parameter models and a two-parameter model of
Fermat type Calabi-Yau manifolds.Comment: 27 pages, LaTeX, no figure
AdS_3/CFT_2 Correspondence and Space-Time N=3 Superconformal Algebra
We study a Wess-Zumino-Witten model with target space AdS_3 x (S^3 x S^3 x
S^1)/Z_2. This allows us to construct space-time N=3 superconformal theories.
By combining left-, and right-moving parts through a GSO and a Z_2 projections,
a new asymmetric (N,\bar{N})=(3,1) model is obtained. It has an extra gauge
(affine) SU(2) symmetry in the target space of the type IIA string. An
associated configuration is realized as slantwise intersecting M5-M2 branes
with a Z_2-fixed plane in the M-theory viewpoint.Comment: 27 pages, 1 figure, final versio
Simulation of Slow Light with Electronics Circuits
We present an electronic circuit which simulates wave propagation in
dispersive media. The circuit is an array of phase shifter composed of
operational amplifiers and can be described with a discretized version of
one-dimensional wave equation for envelopes. The group velocity can be changed
both spatially and temporarily. It is used to emulate slow light or stopped
light, which has been realized in a medium with electromagnetically induced
transparency (EIT). The group-velocity control of optical pulses is expected to
be a useful tool in the field of quantum information and communication.Comment: The following article has been submitted to the American Journal of
Physics. After it is published, it will be found at
http://scitation.aip.org/ajp (7 pages, 7 figures
Generation of photon pairs using polarization-dependent two-photon absorption
We propose a new method for generating photon pairs from coherent light using
polarization-dependent two-photon absorption. We study the photon statistics of
two orthogonally polarized modes by solving a master equation, and show that
when we prepare a coherent state in one polarization mode, photon pairs are
created in the other mode. The photon pairs have the same frequency as that of
the incident light.Comment: 4 pages, 3 figures, submitted to PR
Demonstration of negative group delays in a simple electronic circuit
We present a simple electronic circuit which produces negative group delays
for base-band pulses. When a band-limited pulse is applied as the input, a
forwarded pulse appears at the output. The negative group delays in lumped
systems share the same mechanism with the superluminal light propagation, which
is recently demonstrated in an absorption-free, anomalous dispersive medium
[Wang et al., Nature 406, 277 (2000)]. In this circuit, the advance time more
than twenty percent of the pulse width can easily be achieved. The time
constants, which can be in the order of seconds, is slow enough to be observed
with the naked eye by looking at the lamps driven by the pulses.Comment: 6pages,8 figure
Lattice Boltzmann Simulations of Droplet formation in confined Channels with Thermocapillary flows
Based on mesoscale lattice Boltzmann simulations with the "Shan-Chen" model,
we explore the influence of thermocapillarity on the break-up properties of
fluid threads in a microfluidic T-junction, where a dispersed phase is injected
perpendicularly into a main channel containing a continuous phase, and the
latter induces periodic break-up of droplets due to the cross-flowing.
Temperature effects are investigated by switching on/off both positive/negative
temperature gradients along the main channel direction, thus promoting a
different thread dynamics with anticipated/delayed break-up. Numerical
simulations are performed at changing the flow-rates of both the continuous and
dispersed phases, as well as the relative importance of viscous forces, surface
tension forces and thermocapillary stresses. The range of parameters is broad
enough to characterize the effects of thermocapillarity on different mechanisms
of break-up in the confined T-junction, including the so-called "squeezing" and
"dripping" regimes, previously identified in the literature. Some simple
scaling arguments are proposed to rationalize the observed behaviour, and to
provide quantitative guidelines on how to predict the droplet size after
break-up.Comment: 18 pages, 9 figure
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