302 research outputs found
Motions of the String Solutions in the XXZ Spin Chain under a Varying Twist
We determine the motions of the roots of the Bethe ansatz equation for the
ground state in the XXZ spin chain under a varying twist angle. This is done by
analytic as well as numerical study at a finite size system. In the attractive
critical regime , we reveal intriguing motions of strings due
to the finite size corrections to the length of the strings: in the case of
two-strings, the roots collide into the branch points perpendicularly to the
imaginary axis, while in the case of three-strings, they fluctuate around the
center of the string. These are successfully generalized to the case of
-string. These results are used to determine the final configuration of the
momenta as well as that of the phase shift functions. We obtain these as well
as the period and the Berry phase also in the regime ,
establishing the continuity of the previous results at to
this regime. We argue that the Berry phase can be used as a measure of the
statistics of the quasiparticle ( or the bound state) involved in the process.Comment: An important reference is added and mentioned at the end of the tex
Massive Scaling Limit of beta-Deformed Matrix Model of Selberg Type
We consider a series of massive scaling limits m_1 -> infty, q -> 0, lim m_1
q = Lambda_{3} followed by m_4 -> infty, Lambda_{3} -> 0, lim m_4 Lambda_{3} =
(Lambda_2)^2 of the beta-deformed matrix model of Selberg type (N_c=2, N_f=4)
which reduce the number of flavours to N_f=3 and subsequently to N_f=2. This
keeps the other parameters of the model finite, which include n=N_L and
N=n+N_R, namely, the size of the matrix and the "filling fraction". Exploiting
the method developed before, we generate instanton expansion with finite g_s,
epsilon_{1,2} to check the Nekrasov coefficients (N_f =3,2 cases) to the lowest
order. The limiting expressions provide integral representation of irregular
conformal blocks which contains a 2d operator lim frac{1}{C(q)} : e^{(1/2)
\alpha_1 \phi(0)}: (int_0^q dz : e^{b_E phi(z)}:)^n : e^{(1/2) alpha_2 phi(q)}:
and is subsequently analytically continued.Comment: LaTeX, 21 pages; v2: a reference adde
Surface MIMO: Using Conductive Surfaces For MIMO Between Small Devices
As connected devices continue to decrease in size, we explore the idea of
leveraging everyday surfaces such as tabletops and walls to augment the
wireless capabilities of devices. Specifically, we introduce Surface MIMO, a
technique that enables MIMO communication between small devices via surfaces
coated with conductive paint or covered with conductive cloth. These surfaces
act as an additional spatial path that enables MIMO capabilities without
increasing the physical size of the devices themselves. We provide an extensive
characterization of these surfaces that reveal their effect on the propagation
of EM waves. Our evaluation shows that we can enable additional spatial streams
using the conductive surface and achieve average throughput gains of 2.6-3x for
small devices. Finally, we also leverage the wideband characteristics of these
conductive surfaces to demonstrate the first Gbps surface communication system
that can directly transfer bits through the surface at up to 1.3 Gbps.Comment: MobiCom '1
Uniqueness and examples of compact toric Sasaki-Einstein metrics
In [11] it was proved that, given a compact toric Sasaki manifold of positive
basic first Chern class and trivial first Chern class of the contact bundle,
one can find a deformed Sasaki structure on which a Sasaki-Einstein metric
exists. In the present paper we first prove the uniqueness of such Einstein
metrics on compact toric Sasaki manifolds modulo the action of the identity
component of the automorphism group for the transverse holomorphic structure,
and secondly remark that the result of [11] implies the existence of compatible
Einstein metrics on all compact Sasaki manifolds obtained from the toric
diagrams with any height, or equivalently on all compact toric Sasaki manifolds
whose cones have flat canonical bundle. We further show that there exists an
infinite family of inequivalent toric Sasaki-Einstein metrics on for each positive integer .Comment: Statements of the results are modifie
Complete Set of Commuting Symmetry Operators for the Klein-Gordon Equation in Generalized Higher-Dimensional Kerr-NUT-(A)dS Spacetimes
We consider the Klein-Gordon equation in generalized higher-dimensional
Kerr-NUT-(A)dS spacetime without imposing any restrictions on the functional
parameters characterizing the metric. We establish commutativity of the
second-order operators constructed from the Killing tensors found in
arXiv:hep-th/0612029 and show that these operators, along with the first-order
operators originating from the Killing vectors, form a complete set of
commuting symmetry operators (i.e., integrals of motion) for the Klein-Gordon
equation. Moreover, we demonstrate that the separated solutions of the
Klein-Gordon equation obtained in arXiv:hep-th/0611245 are joint eigenfunctions
for all of these operators. We also present explicit form of the zero mode for
the Klein-Gordon equation with zero mass.
In the semiclassical approximation we find that the separated solutions of
the Hamilton-Jacobi equation for geodesic motion are also solutions for a set
of Hamilton-Jacobi-type equations which correspond to the quadratic conserved
quantities arising from the above Killing tensors.Comment: 6 pages, no figures; typos in eq.(6) fixed; one reference adde
Normalization of Off-shell Boundary State, g-function and Zeta Function Regularization
We consider the model in two dimensions with boundary quadratic deformation
(BQD), which has been discussed in tachyon condensation. The partition function
of this model (BQD) on a cylinder is determined, using the method of zeta
function regularization. We show that, for closed channel partition function, a
subtraction procedure must be introduced in order to reproduce the correct
results at conformal points. The boundary entropy (g-function) is determined
from the partition function and the off-shell boundary state. We propose and
consider a supersymmetric generalization of BQD model, which includes a
boundary fermion mass term, and check the validity of the subtraction
procedure.Comment: 21 pages, LaTeX, comments and 3 new references adde
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