247 research outputs found
VISITOR PREFERENCES AND VALUES FOR WATER-BASED RECREATION: A CASE STUDY OF THE OCALA NATIONAL FOREST
We used the open-ended contingent valuation method to elicit willingnes to pay (WTP) for day visitors and extended visitors on the Ocala National Forest (ONF), Florida. A Tobit model specification was applied to account for the issues involved with censored WTP bids. The results reveal that visitors would pay more for improved recreational facilities at the ONF. In particular, our estimates show that visitors would pay 1.9 million for moderate improvements, and $2.5 million for more improvements.contingent valuation, Tobit analysis, water-based recreation, Resource /Energy Economics and Policy, Q23, Q26,
PP Wave Limit and Enhanced Supersymmetry in Gauge Theories
We observe that the pp wave limit of compactifications of
type IIB string theory is universal, and maximally supersymmetric, as long as
is smooth and preserves some supersymmetry. We investigate a specific
case, . The dual SCFT, describing D3-branes at a
conifold singularity, has operators that we identify with the oscillators of
the light-cone string in the universal pp-wave background. The correspondence
is remarkable in that it relies on the exact spectrum of anomalous dimensions
in this CFT, along with the existence of certain exceptional series of
operators whose dimensions are protected only in the limit of large `t Hooft
coupling. We also briefly examine the singular case , for which
the pp wave background becomes a orbifold of the maximally supersymmetric
background by reflection of 4 transverse coordinates. We find operators in the
corresponding SCFT with the right properties to describe both the
untwisted and the twisted sectors of the closed string.Comment: 15 pages, LaTeX; v2: added more detail to a derivation, and a
preprint number; v3: minor corrections, some remarks and references adde
Supermembranes and Super Matrix Models
We review recent developments in the theory of supermembranes and their
relation to matrix models.Comment: Invited lecture presented at the Corfu Workshop, September 20 - 26,
1998, of the TMR Project "Quantum Aspects of Gauge Theories, Supersymmetry
and Unification" (ERBFMRXCT96-0045), to appear in the proceedings. Latex 41
p
Gauge Theory and the Excision of Repulson Singularities
We study brane configurations that give rise to large-N gauge theories with
eight supersymmetries and no hypermultiplets. These configurations include a
variety of wrapped, fractional, and stretched branes or strings. The
corresponding spacetime geometries which we study have a distinct kind of
singularity known as a repulson. We find that this singularity is removed by a
distinctive mechanism, leaving a smooth geometry with a core having an enhanced
gauge symmetry. The spacetime geometry can be related to large-N Seiberg-Witten
theory.Comment: 31 pages LaTeX, 2 figures (v3: references added
Yang-Mills Duals for Semiclassical Strings
We consider a semiclassical multiwrapped circular string pulsating on S_5,
whose center of mass has angular momentum J on an S_3 subspace. Using the
AdS/CFT correspondence we argue that the one-loop anomalous dimension of the
dual operator is a simple rational function of J/L, where J is the R-charge and
L is the bare dimension of the operator. We then reproduce this result directly
from a super Yang-Mills computation, where we make use of the integrability of
the one-loop system to set up an integral equation that we solve. We then
verify the results of Frolov and Tseytlin for circular rotating strings with
R-charge assignment (J',J',J). In this case we solve for an integral equation
found in the O(-1) matrix model when J' J.
The latter region starts at J'=L/2 and continues down, but an apparent critical
point is reached at J'=4J. We argue that the critical point is just an artifact
of the Bethe ansatz and that the conserved charges of the underlying integrable
model are analytic for all J' and that the results from the O(-1) model
continue onto the results of the O(+1) model.Comment: 26 Pages, LaTeX; v2 Typos corrected, reference update
Digital Simulation for Automobile Maneuvers
A new all-digital simulation of automobile handling allows severe maneuvers involving braking or accel eration and cornering. A novel feature is the in corporation of closed-loop control based on a mathematical model of the human driver. The program is modular and well-documented. The model includes provisions for nonlinear tire and suspension forces and moments; it also allows the user to switch off the nonlinearities and to include an antilock brake system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68886/2/10.1177_003754978103700304.pd
Multiple CDM cosmology with string landscape features and future singularities
Multiple CDM cosmology is studied in a way that is formally a
classical analog of the Casimir effect. Such cosmology corresponds to a
time-dependent dark fluid model or, alternatively, to its scalar field
presentation, and it motivated by the string landscape picture. The future
evolution of the several dark energy models constructed within the scheme is
carefully investigated. It turns out to be almost always possible to choose the
parameters in the models so that they match the most recent and accurate
astronomical values. To this end, several universes are presented which mimick
(multiple) CDM cosmology but exhibit Little Rip, asymptotically de
Sitter, or Type I, II, III, and IV finite-time singularity behavior in the far
future, with disintegration of all bound objects in the cases of Big Rip,
Little Rip and Pseudo-Rip cosmologies.Comment: LaTeX 11 pages, 10 figure
Stringing Spins and Spinning Strings
We apply recently developed integrable spin chain and dilatation operator
techniques in order to compute the planar one-loop anomalous dimensions for
certain operators containing a large number of scalar fields in N =4 Super
Yang-Mills. The first set of operators, belonging to the SO(6) representations
[J,L-2J,J], interpolate smoothly between the BMN case of two impurities (J=2)
and the extreme case where the number of impurities equals half the total
number of fields (J=L/2). The result for this particular [J,0,J] operator is
smaller than the anomalous dimension derived by Frolov and Tseytlin
[hep-th/0304255] for a semiclassical string configuration which is the dual of
a gauge invariant operator in the same representation. We then identify a
second set of operators which also belong to [J,L-2J,J] representations, but
which do not have a BMN limit. In this case the anomalous dimension of the
[J,0,J] operator does match the Frolov-Tseytlin prediction. We also show that
the fluctuation spectra for this [J,0,J] operator is consistent with the string
prediction.Comment: 27 pages, 4 figures, LaTex; v2 reference added, typos fixe
Conformal Affine Toda Soliton and Moduli of IIB Superstring on
In this paper we interpret the hidden symmetry of the moduli space of IIB
superstring on in terms of the chiral embedding in
, which turns to be the conformal affine Toda model.
We review how the position of poles in the Riemann-Hilbert formulation
of dressing transformation and how the value of loop parameters in the
vertex operator of affine algebra determines the moduli space of the soliton
solutions, which describes the moduli space of the Green-Schwarz superstring.
We show also how this affine SU(4) symmetry affinize the conformal symmetry in
the twistor space, and how a soliton string corresponds to a Robinson
congruence with twist and dilation spin coefficients of twistor.Comment: Final version, Misprints corrected, Note adde
Ghost D-branes
We define a ghost D-brane in superstring theories as an object that cancels
the effects of an ordinary D-brane. The supergroups U(N|M) and OSp(N|M) arise
as gauge symmetries in the supersymmetric world-volume theory of D-branes and
ghost D-branes. A system with a pair of D-brane and ghost D-brane located at
the same location is physically equivalent to the closed string vacuum. When
they are separated, the system becomes a new brane configuration. We generalize
the type I/heterotic duality by including n ghost D9-branes on the type I side
and by considering the heterotic string whose gauge group is OSp(32+2n|2n).
Motivated by the type IIB S-duality applied to D9- and ghost D9-branes, we also
find type II-like closed superstrings with U(n|n) gauge symmetry.Comment: 49 pages, 6 figures, harvmac. v2: references and acknowledgements
adde
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