329 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
Kerr-Schild Structure and Harmonic 2-forms on (A)dS-Kerr-NUT Metrics
We demonstrate that the general (A)dS-Kerr-NUT solutions in D dimensions with
([D/2], [(D+1)/2]) signature admit [D/2] linearly-independent,
mutually-orthogonal and affinely-parameterised null geodesic congruences. This
enables us to write the metrics in a multi-Kerr-Schild form, where the mass and
all of the NUT parameters enter the metrics linearly. In the case of D=2n, we
also obtain n harmonic 2-forms, which can be viewed as charged (A)dS-Kerr-NUT
solution at the linear level of small-charge expansion, for the
higher-dimensional Einstein-Maxwell theories. In the BPS limit, these 2-forms
reduce to n-1 linearly-independent ones, whilst the resulting Calabi-Yau metric
acquires a Kahler 2-form, leaving the total number the same.Comment: Latex, 11 pages, references adde
Resolutions of Cones over Einstein-Sasaki Spaces
Recently an explicit resolution of the Calabi-Yau cone over the inhomogeneous
five-dimensional Einstein-Sasaki space Y^{2,1} was obtained. It was constructed
by specialising the parameters in the BPS limit of recently-discovered
Kerr-NUT-AdS metrics in higher dimensions. We study the occurrence of such
non-singular resolutions of Calabi-Yau cones in a more general context.
Although no further six-dimensional examples arise as resolutions of cones over
the L^{pqr} Einstein-Sasaki spaces, we find general classes of non-singular
cohomogeneity-2 resolutions of higher-dimensional Einstein-Sasaki spaces. The
topologies of the resolved spaces are of the form of an R^2 bundle over a base
manifold that is itself an bundle over an Einstein-Kahler manifold.Comment: Latex, 23 page
Scattering of Plane Waves in Self-Dual Yang-Mills Theory
We consider the classical self-dual Yang-Mills equation in 3+1-dimensional
Minkowski space. We have found an exact solution, which describes scattering of
plane waves. In order to write the solution in a compact form, it is
convenient to introduce a scattering operator . It acts in the direct
product of three linear spaces: 1) universal enveloping of Lie algebra,
2) -dimensional vector space and 3) space of functions defined on the unit
interval.Comment: 16 pages, LaTeX fil
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
Exact form factors for the scaling Z{N}-Ising and the affine A{N-1}-Toda quantum field theories
Previous results on form factors for the scaling Ising and the sinh-Gordon
models are extended to general -Ising and affine -Toda quantum
field theories. In particular result for order, disorder parameters and
para-fermi fields and are
presented for the -model. For the -Toda model all form factors
for exponentials of the Toda fields are proposed. The quantum field equation of
motion is proved and the mass and wave function renormalization are calculated
exactly.Comment: Latex, 11 page
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