706 research outputs found
Schnabl's L_0 Operator in the Continuous Basis
Following Schnabl's analytic solution to string field theory, we calculate
the operators for a scalar field in the
continuous basis. We find an explicit and simple expression for them
that further simplifies for their sum, which is block diagonal in this basis.
We generalize this result for the bosonized ghost sector, verify their
commutation relation and relate our expressions to wedge state representations.Comment: 1+16 pages. JHEP style. Typos correcte
Comments on Schnabl's analytic solution for tachyon condensation in Witten's open string field theory
Schnabl recently constructed an analytic solution for tachyon condensation in
Witten's open string field theory. The solution consists of two pieces. Only
the first piece is involved in proving that the solution satisfies the equation
of motion when contracted with any state in the Fock space. On the other hand,
both pieces contribute in evaluating the kinetic term to reproduce the value
predicted by Sen's conjecture. We therefore need to understand why the second
piece is necessary. We evaluate the cubic term of the string field theory
action for Schnabl's solution and use it to show that the second piece is
necessary for the equation of motion contracted with the solution itself to be
satisfied. We also present the solution in various forms including a pure-gauge
configuration and provide simpler proofs that it satisfies the equation of
motion.Comment: 33 pages, 4 figures, LaTeX2e; v2: minor changes, version published in
JHE
On surface states and star-subalgebras in string field theory
We elaborate on the relations between surface states and squeezed states.
First, we investigate two different criteria for determining whether a matter
sector squeezed state is also a surface state and show that the two criteria
are equivalent. Then, we derive similar criteria for the ghost sector. Next, we
refine the criterion for determining whether a surface state is in
H_{\kappa^2}, the subalgebra of squeezed states obeying [S,K_1^2]=0. This
enables us to find all the surface states of the H_{\kappa^2} subalgebra, and
show that it consists only of wedge states and (hybrid) butterflies. Finally,
we investigate generalizations of this criterion and find an infinite family of
surface states subalgebras, whose surfaces are described using a "generalized
Schwarz-Christoffel" mapping.Comment: 38 pages, 6 figures, JHEP style; typos corrected, ref. adde
Normalization anomalies in level truncation calculations
We test oscillator level truncation regularization in string field theory by
calculating descent relations among vertices, or equivalently, the overlap of
wedge states. We repeat the calculation using bosonic, as well as fermionic
ghosts, where in the bosonic case we do the calculation both in the discrete
and in the continuous basis. We also calculate analogous expressions in field
level truncation. Each calculation gives a different result. We point out to
the source of these differences and in the bosonic ghost case we pinpoint the
origin of the difference between the discrete and continuous basis
calculations. The conclusion is that level truncation regularization cannot be
trusted in calculations involving normalization of singular states, such as
wedge states, rank-one squeezed state projectors and string vertices.Comment: 1+20 pages, 6 figures. v2: Ref. added, typos correcte
Modelling-based identification of factors influencing campylobacters in chicken broiler houses and on carcasses sampled after processing and chilling
Publication history: Accepted - 30 January 2017; Published online - 4 March 2017.Aims: To identify production and processing practices that might reduceCampylobacter numbers contaminating chicken broiler carcasses.Methods and Results: The numbers of campylobacters were determined oncarcass neck skins after processing or in broiler house litter samples.Supplementary information that described farm layouts, farming conditions forindividual ïŹocks, the slaughterhouse layouts and operating conditions insideplants was collected, matched with each Campylobacter test result. Statisticalmodels predicting the numbers of campylobacters on neck skins and in litterwere constructed. Carcass microbial contamination was more stronglyinïŹuenced by on-farm production practices compared with slaughterhouseactivities. We observed correlations between the chilling, washing anddefeathering stages of processing and the numbers of campylobacters oncarcasses. There were factors on farm that also correlated with numbers ofcampylobacters in litter. These included bird gender, the exclusion of dogsfrom houses, beetle presence in the house litter and the materials used toconstruct the house frame.Conclusions: Changes in farming practices have greater potential for reducingchicken carcass microbial contamination compared with processinginterventions.SigniïŹcance and Impact of the Study: Routine commercial practices wereidentiïŹed that were correlated with lowered numbers of campylobacters.Consequently, these practices are likely to be both cost-effective and suitablefor adoption into established farms and commercial processingThis work was funded by the United Kingdom Food Standards Agency (FSA) as projects FS241051A and FS101123
Coronal mass ejections as expanding force-free structures
We mode Solar coronal mass ejections (CMEs) as expanding force-fee magnetic
structures and find the self-similar dynamics of configurations with spatially
constant \alpha, where {\bf J} =\alpha {\bf B}, in spherical and cylindrical
geometries, expanding spheromaks and expanding Lundquist fields
correspondingly. The field structures remain force-free, under the conventional
non-relativistic assumption that the dynamical effects of the inductive
electric fields can be neglected. While keeping the internal magnetic field
structure of the stationary solutions, expansion leads to complicated internal
velocities and rotation, induced by inductive electric field. The structures
depends only on overall radius R(t) and rate of expansion \dot{R}(t) measured
at a given moment, and thus are applicable to arbitrary expansion laws. In case
of cylindrical Lundquist fields, the flux conservation requires that both axial
and radial expansion proceed with equal rates. In accordance with observations,
the model predicts that the maximum magnetic field is reached before the
spacecraft reaches the geometric center of a CME.Comment: 19 pages, 9 Figures, accepted by Solar Physic
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
Virasoro operators in the continuous basis of string field theory
In this work we derive two important tools for working in the \kappa basis of
string field theory. First we give an analytical expression for the finite part
of the spectral density \rho_{fin}. This expression is relevant when both
matter and ghost sectors are considered. Then we calculate the form of the
matter part of the Virasoro generators L_n in the \kappa basis, which construct
string field theory's derivation Q_{BRST}. We find that the Virasoro generators
are given by one dimensional delta functions with complex arguments.Comment: 16 page
Density functional study of Au (n=2-20) clusters: lowest-energy structures and electronic properties
We have investigated the lowest-energy structures and electronic properties
of the Au(n=2-20) clusters based on density functional theory (DFT) with
local density approximation. The small Au clusters adopt planar structures
up to n=6. Tabular cage structures are preferred in the range of n=10-14 and a
structural transition from tabular cage-like structure to compact
near-spherical structure is found around n=15. The most stable configurations
obtained for Au and Au clusters are amorphous instead of
icosahedral or fcc-like, while the electronic density of states sensitively
depend on the cluster geometry. Dramatic odd-even alternative behaviors are
obtained in the relative stability, HOMO-LUMO gaps and ionization potentials of
gold clusters. The size evolution of electronic properties is discussed and the
theoretical ionization potentials of Au clusters compare well with
experiments.Comment: 6 pages, 7 figure
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
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