584 research outputs found
Noncentrosymmetric plasmon modes and giant terahertz photocurrent in a two-dimensional plasmonic crystal
We introduce and theoretically study the plasmon-photogalvanic effect in the
planar noncentrosymmetric plasmonic crystal containing a homogeneous
two-dimensional electron system gated by a periodic metal grating with an
asymmetric unit cell. The plasmon-photogalvanic DC current arises due to the
two-dimensional electron drag by the noncentrosymmetric plasmon modes excited
under normal incidence of terahertz radiation. We show that the collective
plasmon modes of the planar plasmonic crystal become strongly
noncentrosymmetric in the weak coupling regime of their anticrossing. Large
plasmon wavevector (which is typically by two-three orders of magnitude greater
than the terahertz photon wavevector) along with strong near-field enhancement
at the plasmon resonance make the plasmonic drag a much stronger effect
compared to the photon drag observed in conventional two-dimensional electron
systems.Comment: 9 pages, 10 figures, submitted to Physical Review
A_{N-1} conformal Toda field theory correlation functions from conformal N=2 SU(N) quiver gauge theories
We propose a relation between correlation functions in the 2d A_{N-1}
conformal Toda theories and the Nekrasov instanton partition functions in
certain conformal N=2 SU(N) 4d quiver gauge theories. Our proposal generalises
the recently uncovered relation between the Liouville theory and SU(2) quivers.
New features appear in the analysis that have no counterparts in the Liouville
case.Comment: 23 pages. v2: some typos correcte
Sigma models as perturbed conformal field theories
We show that two-dimensional sigma models are equivalent to certain perturbed
conformal field theories. When the fields in the sigma model take values in a
space G/H for a group G and a maximal subgroup H, the corresponding conformal
field theory is the limit of the coset model , and the
perturbation is related to the current of G. This correspondence allows us for
example to find the free energy for the "O(n)" (=O(n)/O(n-1)) sigma model at
non-zero temperature. It also results in a new approach to the CP^{n} model.Comment: 4 pages. v2: corrects typos (including several in the published
version
Lattice algebras and quantum groups
We represent Feigin's construction [22] of lattice W algebras and give some
simple results: lattice Virasoro and algebras. For simplest case
we introduce whole quantum group on this lattice. We
find simplest two-dimensional module as well as exchange relations and define
lattice Virasoro algebra as algebra of invariants of . Another
generalization is connected with lattice integrals of motion as the invariants
of quantum affine group . We show that Volkov's scheme leads
to the system of difference equations for the function from non-commutative
variables.Comment: 13 pages, misprints have been correcte
parafermions from constrained WZNW theories
The conformal field theory based on the coset construction is
treated as the WZNW theory for the affine Lie algebra with the
constrained subalgebra.Using a modification of the generalized
canonical quantization method generators and primary fields of an extended
symmetry algebra are found for arbitrary d.Comment: 14 pages,latex,misprints in formulas 26,40,45 corrected,a reference
adde
Some remarks on D-branes and defects in Liouville and Toda field theories
In this paper we analyze the Cardy-Lewellen equation in general diagonal
model. We show that in these models it takes simple form due to some general
properties of conformal field theories, like pentagon equations and OPE
associativity. This implies, that the Cardy-Lewellen equation has simple form
also in non-rational diagonal models. We specialize our finding to the
Liouville and Toda field theories. In particular we prove, that conjectured
recently defects in Toda field theory indeed satisfy the cluster equation. We
also derive the Cardy-Lewellen equation in all Toda field theories and
prove that the forms of boundary states found recently in Toda field
theory hold in all theories as well.Comment: 30 pages, some comments, explanations and references adde
ZZ-Branes of N=2 Super-Liouville Theory
We study conformal boundary conditions and corresponding one-point functions
of the N=2 super-Liouville theory using both conformal and modular bootstrap
methods. We have found both continuous (`FZZT-branes') and discrete
(`ZZ-branes') boundary conditions. In particular, we identify two different
types of the discrete ZZ-brane solutions, which are associated with degenerate
fields of the N=2 super-Liouville theory.Comment: 26 page
Plasmonic terahertz detection by a double-grating-gate field-effect transistor structure with an asymmetric unit cell
Plasmonic terahertz detection by a double-grating gate field-effect
transistor structure with an asymmetric unit cell is studied theoretically.
Detection responsivity exceeding 8 kV/W at room temperature in the photovoltaic
response mode is predicted for strong asymmetry of the structure unit cell.
This value of the responsivity is an order of magnitude greater than reported
previously for the other types of uncooled plasmonic terahertz detectors. Such
enormous responsivity can be obtained without using any supplementary antenna
elements because the double-grating gate acts as an aerial matched antenna that
effectively couples the incoming terahertz radiation to plasma oscillations in
the structure channel.Comment: Submitted to APL, 8 pages, 2 figure
Exact Results for Thermodynamics of the Classical Field Theories: Sine- and Sinh-Gordon Models
Using the recently obtained exact results for the expectation values of
operators in the sine- and sinh-Gordon models [A. B. Zamolodchikov and S.
Lukyanov, Nucl. Phys. B{\bf 493}, 571 (1997), V. Fateev, S. Lukyanov, A. B.
Zamolodchikov and Al. B. Zamolodchikov, Phys. Lett. B{\bf 406}, 83 (1997)] we
calculate the specific heat of the corresponding two dimensional Euclidean
(classical) models.
We show that the temperature dependence of the specific heat of the
sine-Gordon model, in the commensurate phase, has a maximum well below the
Kosterlitz-Thouless transition and that the sinh-Gordon model is
thermodynamically unstable in the strong coupling regime. We give also the
temperature dependence of the specific heat in the incommensurate phase of the
sine-Gordon model.Comment: 14 pages, including 6 figures; updated version; submitted to Phys.
Rev.
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