1,010 research outputs found
Open Superstring Star as a Continuous Moyal Product
By diagonalizing the three-string vertex and using a special coordinate
representation the matter part of the open superstring star is identified with
the continuous Moyal product of functions of anti-commuting variables. We show
that in this representation the identity and sliver have simple expressions.
The relation with the half-string fermionic variables in continuous basis is
given.Comment: Latex, 19 pages; more comments added and notations are simplifie
Gauge Invariance and Tachyon Condensation in Cubic Superstring Field Theory
The gauge invariance of cubic open superstring field theory is considered in
a framework of level truncation, and applications to the tachyon condensation
problem are discussed. As it is known, in the bosonic case the Feynman-Siegel
gauge is not universal within the level truncation method. We explore another
gauge that is more suitable for calculation of the tachyon potential for
fermionic string at level (2,6). We show that this new gauge has no
restrictions on the region of its validity at least at this level.Comment: 21 pages, 2 figures, LaTeX 2e; references added, typos correcte
String Field Theory Projectors for Fermions of Integral Weight
The interaction vertex for a fermionic first order system of weights (1,0)
such as the twisted bc-system, the fermionic part of N=2 string field theory
and the auxiliary \eta\xi system of N=1 strings is formulated in the Moyal
basis. In this basis, the Neumann matrices are diagonal; as usual, the
eigenvectors are labeled by \kappa\in\R. Oscillators constructed from these
eigenvectors make up two Clifford algebras for each nonzero value of \kappa.
Using a generalization of the Moyal-Weyl map to the fermionic case, we classify
all projectors of the star-algebra which factorize into projectors for each
\kappa-subspace. At least for the case of squeezed states we recover the full
set of bosonic projectors with this property. Among the subclass of ghost
number-homogeneous squeezed state projectors, we find a single class of
BPZ-real states parametrized by one (nearly) arbitrary function of \kappa. This
class is shown to contain the generalized butterfly states. Furthermore, we
elaborate on sufficient and necessary conditions which have to be fulfilled by
our projectors in order to constitute surface states. As a byproduct we find
that the full star product of N=2 string field theory translates into a
canonically normalized continuous tensor product of Moyal-Weyl products up to
an overall normalization. The divergent factors arising from the translation to
the continuous basis cancel between bosons and fermions in any even dimension.Comment: LaTeX, 1+23 pages, minor improvements, references adde
Electronic damping of molecular motion at metal surfaces
A method for the calculation of the damping rate due to electron-hole pair
excitation for atomic and molecular motion at metal surfaces is presented. The
theoretical basis is provided by Time Dependent Density Functional Theory
(TDDFT) in the quasi-static limit and calculations are performed within a
standard plane-wave, pseudopotential framework. The artificial periodicity
introduced by using a super-cell geometry is removed to derive results for the
motion of an isolated atom or molecule, rather than for the coherent motion of
an ordered over-layer. The algorithm is implemented in parallel, distributed
across both and space, and in a form compatible with the
CASTEP code. Test results for the damping of the motion of hydrogen atoms above
the Cu(111) surface are presented.Comment: 10 pages, 3 figure
Witten's Vertex Made Simple
The infinite matrices in Witten's vertex are easy to diagonalize. It just
requires some SL(2,R) lore plus a Watson-Sommerfeld transformation. We
calculate the eigenvalues of all Neumann matrices for all scale dimensions s,
both for matter and ghosts, including fractional s which we use to regulate the
difficult s=0 limit. We find that s=1 eigenfunctions just acquire a p term, and
x gets replaced by the midpoint position.Comment: 24 pages, 2 figures, RevTeX style, typos correcte
Momentum-Transfer to and Elementary-Excitations of a Bose-Einstein Condensate by a Time-Dependent Optical Potential
We present results of calculations on Bose-Einstein condensed Rb atoms
subjected to a moving standing-wave light-potential of the form . We calculate the mean-field dynamics (the order
paramter) of the condensate and determine the resulting condensate momentum in
the direction, , where is the peak optical
potential strength and is the pulse duration. Although the local density
approximation for the Bogoliubov excitation spectral distribution is a good
approximation for very low optical intensities, long pulse duration and
sufficiently large values of the wavevector of the light-potential, for
small , short duration pulses, or for not-so-low intensities, the local
density perturbative description of the excitation spectrum breaks down badly,
as shown by our results.Comment: 8 pages, 7 figure
Vacuum String Field Theory ancestors of the GMS solitons
We define a sequence of VSFT D-branes whose low energy limit leads exactly to
a corresponding sequence of GMS solitons. The D-branes are defined by acting on
a fixed VSFT lump with operators defined by means of Laguerre polynomials whose
argument is quadratic in the string creation operators. The states obtained in
this way form an algebra under the SFT star product, which is isomorphic to a
corresponding algebra of GMS solitons under the Moyal product. In order to
obtain a regularized field theory limit we embed the theory in a constant
background B field.Comment: 1+16 pages; v2: typos corrected; v3: two appendices added, final
versio
Fermionic Ghosts in Moyal String Field Theory
We complete the construction of the Moyal star formulation of bosonic open
string field theory (MSFT) by providing a detailed study of the fermionic ghost
sector. In particular, as in the case of the matter sector, (1) we construct a
map from Witten's star product to the Moyal product, (2) we propose a
regularization scheme which is consistent with the matter sector and (3) as a
check of the formalism, we derive the ghost Neumann coefficients algebraically
directly from the Moyal product. The latter satisfy the Gross-Jevicki nonlinear
relations even in the presence of the regulator, and when the regulator is
removed they coincide numerically with the expression derived from conformal
field theory. After this basic construction, we derive a regularized action of
string field theory in the Siegel gauge and define the Feynman rules. We give
explicitly the analytic expression of the off-shell four point function for
tachyons, including the ghost contribution. Some of the results in this paper
have already been used in our previous publications. This paper provides the
technical details of the computations which were omitted there.Comment: 65 pages, typos correcte
On Continuous Moyal Product Structure in String Field Theory
We consider a diagonalization of Witten's star product for a ghost system of
arbitrary background charge and Grassmann parity. To this end we use a
bosonized formulation of such systems and a spectral analysis of Neumann
matrices. We further identify a continuous Moyal product structure for a
combined ghosts+matter system. The normalization of multiplication kernel is
discussed.Comment: 18+7 pages, 1 figure, typos correction
Cubic String Field Theory in pp-wave Background and Background Independent Moyal Structure
We study Witten open string field theory in the pp-wave background in the
tensionless limit, and construct the N-string vertex in the basis which
diagonalizes the string perturbative spectrum. We found that the Witten
*-product can be viewed as infinite copies of the Moyal product with the same
noncommutativity parameter . Moreover, we show that this Moyal
structure is universal in the sense that, written in the string bit basis,
Witten's *-product for any background can always be given in terms of the
above-mentioned Moyal structure. We identify some projective operators in this
algebra that we argue to correspond to D-branes of the theory.Comment: Latex, 23 pages, reference adde
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