330 research outputs found
BRST Invariance of Non-local Charges and Monodromy Matrix of Bosonic String on AdS(5)xS(5)
Using the generalized Hamiltonian method of Batalin, Fradkin and Vilkovsky we
develop the BRST formalism for the bosonic string on AdS(5)xS(5) formulated as
principal chiral model. Then we show that the monodromy matrix and non-local
charges are BRST invariant.Comment: 26. page
Plastic flow of persistent currents in two dimensional strongly interacting systems
The local persistent current in two dimensional strongly interacting systems
is investigated. As the interaction strength is enhanced the current in the
sample undergoes a transition from diffusive to ordered flow. The strong
interacting flow has the characteristics of a plastic flow through dislocations
in the pinned charge density wave which develops in the system at low
densities.Comment: 12 pages, 4 figures, accepted for publication in Phys. Rev. B (RC
Multiloop Superstring Amplitudes from Non-Minimal Pure Spinor Formalism
Using the non-minimal version of the pure spinor formalism, manifestly
super-Poincare covariant superstring scattering amplitudes can be computed as
in topological string theory without the need of picture-changing operators.
The only subtlety comes from regularizing the functional integral over the pure
spinor ghosts. In this paper, it is shown how to regularize this functional
integral in a BRST-invariant manner, allowing the computation of arbitrary
multiloop amplitudes. The regularization method simplifies for scattering
amplitudes which contribute to ten-dimensional F-terms, i.e. terms in the
ten-dimensional superspace action which do not involve integration over the
maximum number of 's.Comment: 23 pages harvmac, added acknowledgemen
Non-BPS D-Branes in Light-Cone Green-Schwarz Formalism
Non-BPS D-branes are difficult to describe covariantly in a manifestly
supersymmetric formalism. For definiteness we concentrate on type IIB string
theory in flat background in light-cone Green-Schwarz formalism. We study both
the boundary state and the boundary conformal field theory descriptions of
these D-branes with manifest SO(8) covariance and go through various
consistency checks. We analyze Sen's original construction of non-BPS D-branes
given in terms of an orbifold boundary conformal field theory. We also directly
study the relevant world-sheet theory by deriving the open string boundary
condition from the covariant boundary state. Both these methods give the same
open string spectrum which is consistent with the boundary state, as required
by the world-sheet duality. The boundary condition found in the second method
is given in terms of bi-local fields that are quadratic in Green-Schwarz
fermions. We design a special ``doubling trick'' suitable to handle such
boundary conditions and prescribe rules for computing all possible correlation
functions without boundary insertions. This prescription has been tested by
computing disk one-point functions of several classes of closed string states
and comparing the results with the boundary state computation.Comment: 47 pages, 1 figure. Typos corrected, references added and slight
modification of certain explanation made. Version accepted for publication in
JHE
Towards Vacuum Superstring Field Theory: The Supersliver
We extend some aspects of vacuum string field theory to superstring field
theory in Berkovits' formulation, and we study the star algebra in the
fermionic matter sector. After clarifying the structure of the interaction
vertex in the operator formalism of Gross and Jevicki, we provide an algebraic
construction of the supersliver state in terms of infinite-dimensional
matrices. This state is an idempotent string field and solves the matter part
of the equation of motion of superstring field theory with a pure ghost BRST
operator. We determine the spectrum of eigenvalues and eigenvectors of the
infinite-dimensional matrices of Neumann coefficients in the fermionic matter
sector. We then analyze coherent states based on the supersliver and use them
in order to construct higher-rank projector solutions, as well as to construct
closed subalgebras of the star algebra in the fermionic matter sector. Finally,
we show that the geometric supersliver is a solution to the superstring field
theory equations of motion, including the (super)ghost sector, with the
canonical choice of vacuum BRST operator recently proposed by Gaiotto,
Rastelli, Sen and Zwiebach.Comment: 45 pages, JHEP styl
The signature of a double quantum-dot structure in the I-V characteristics of a complex system
We demonstrate that by carefully analyzing the temperature dependent
characteristics of the I-V measurements for a given complex system it is
possible to determine whether it is composed of a single, double or multiple
quantum-dot structure. Our approach is based on the orthodox theory for a
double-dot case and is capable of simulating I-V characteristics of systems
with any resistance and capacitance values and for temperatures corresponding
to thermal energies larger than the dot level spacing. We compare I-V
characteristics of single-dot and double-dot systems and show that for a given
measured I-V curve considering the possibility of a second dot is equivalent to
decreasing the fit temperature. Thus, our method allows one to gain information
about the structure of an experimental system based on an I-V measurement.Comment: 12 pages 7 figure
Delocalization of tightly bound excitons in disordered systems
The localization length of a low energy tightly bound electron-hole pair
(excitons) is calculated by exact diagonalization for small interacting
disordered systems. The exciton localization length (which corresponds to the
thermal electronic conductance) is strongly enhanced by electron-electron
interactions, while the localization length (pertaining to the charge
conductance) is only slightly enhanced. This shows that the two particle
delocalization mechanism widely discussed for the electron pair case is more
efficient close to the Fermi energy for an electron-hole pair. The relevance to
experiment is also discussed.Comment: 10 pages, 2 figures - old version was posted by mistak
Ground State Spin Structure of Strongly Interacting Disordered 1D Hubbard Model
We study the influence of on-site disorder on the magnetic properties of the
ground state of the infinite U 1D Hubbard model. We find that the ground state
is not ferromagnetic. This is analyzed in terms of the algebraic structure of
the spin dependence of the Hamiltonian. A simple explanation is derived for the
1/N periodicity in the persistent current for this model.Comment: 3 pages, no figure
Making the hyper--K\"ahler structure of N=2 quantum string manifest
We show that the Lorentz covariant formulation of N=2 string in a curved
space reveals an explicit hyper--K\"ahler structure. Apart from the metric, the
superconformal currents couple to a background two--form. By superconformal
symmetry the latter is constrained to be holomorphic and covariantly constant
and allows one to construct three complex structures obeying a
(pseudo)quaternion algebra.Comment: 8 pages, no figures, PACS: 04.60.Ds; 11.30.Pb, Keywords: N=2 string,
hyper-K\"ahler geometry. Presentation improved, references added. The version
to appear in PR
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