204 research outputs found
String Tensions and Three Dimensional Confining Gauge Theories
In the context of gauge/gravity duality, we try to understand better the
proposed duality between the fractional D2-brane supergravity solutions of
(Nucl. Phys. B 606 (2001) 18, hep-th/0101096) and a confining 2+1 dimensional
gauge theory. Based on the similarities between this fractional D2-brane
solution and D3-brane supergravity solutions with more firmly established gauge
theory duals, we conjecture that a confining q-string in the 2+1 dimensional
gauge theory is dual to a wrapped D4-brane. In particular, the D4-brane looks
like a string in the gauge theory directions but wraps a S**3 in S**4 in the
transverse geometry. For one of the supergravity solutions, we find a near
quadratic scaling law for the tension: . Based on the tension,
we conjecture that the gauge theory dual is SU(N) far in the infrared. We also
conjecture that a quadratic or near quadratic scaling is a generic feature of
confining 2+1 dimensional SU(N) gauge theories.Comment: 23 pages, 2 figure
Systematic model behavior of adsorption on flat surfaces
A low density film on a flat surface is described by an expansion involving
the first four virial coefficients. The first coefficient (alone) yields the
Henry's law regime, while the next three correct for the effects of
interactions. The results permit exploration of the idea of universal
adsorption behavior, which is compared with experimental data for a number of
systems
Topological Field Theory and Rational Curves
We analyze the superstring propagating on a Calabi-Yau threefold. This theory
naturally leads to the consideration of Witten's topological non-linear
sigma-model and the structure of rational curves on the Calabi-Yau manifold. We
study in detail the case of the world-sheet of the string being mapped to a
multiple cover of an isolated rational curve and we show that a natural
compactification of the moduli space of such a multiple cover leads to a
formula in agreement with a conjecture by Candelas, de la Ossa, Green and
Parkes.Comment: 20 page
Geometric Constructions of Nongeometric String Theories
We advocate a framework for constructing perturbative closed string
compactifications which do not have large-radius limits. The idea is to augment
the class of vacua which can be described as fibrations by enlarging the
monodromy group around the singular fibers to include perturbative stringy
duality symmetries. As a controlled laboratory for testing this program, we
study in detail six-dimensional (1,0) supersymmetric vacua arising from
two-torus fibrations over a two-dimensional base. We also construct some
examples of two-torus fibrations over four-dimensional bases, and comment on
the extension to other fibrations.Comment: Explanations clarified, typos corrected, references adde
An orientifold of adS_5xT^11 with D7-branes, the associated alpha'^2- corrections and their role in the dual N=1 Sp(2N+2M)xSp(2N) gauge theory
We study the N=1 Sp(2N+2M)xSp(2N) gauge theory on a stack of N physical and M
fractional D3-branes in the background of an orientifolded conifold. The
gravity dual is a type IIB orientifold of adS_5xT^11 (with certain background
fluxes turned on) containing an O7-plane and 8 D7-branes. In the conformal case
(M=0), we argue that the alpha'^2-corrections localized on the 8 D7-branes and
the O7-plane should give vanishing contributions to the supergravity equations
of motion for the bulk fields. In the cascading case (M not equal to 0), we
argue that the alpha'^2-terms give rise to corrections which in the dual
Sp(2N+2M)xSp(2N) gauge theory can be interpreted as corrections to the
anomalous dimensions of the matter fields.Comment: 28 pages, 3 figures, LaTeX; v2: references added; v3: minor change
Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought
The timing of human colonization of East Polynesia, a vast area lying between Hawai‘i, Rapa Nui, and New Zealand, is much debated and the underlying causes of this great migration have been enigmatic. Our study generates evidence for human dispersal into eastern Polynesia from islands to the west from around AD 900 and contemporaneous paleoclimate data from the likely source region. Lake cores from Atiu, Southern Cook Islands (SCIs) register evidence of pig and/or human occupation on a virgin landscape at this time, followed by changes in lake carbon around AD 1000 and significant anthropogenic disturbance from c. AD 1100. The broader paleoclimate context of these early voyages of exploration are derived from the Atiu lake core and complemented by additional lake cores from Samoa (directly west) and Vanuatu (southwest) and published hydroclimate proxies from the Society Islands (northeast) and Kiribati (north). Algal lipid and leaf wax biomarkers allow for comparisons of changing hydroclimate conditions across the region before, during, and after human arrival in the SCIs. The evidence indicates a prolonged drought in the likely western source region for these colonists, lasting c. 200 to 400 y, contemporaneous with the phasing of human dispersal into the Pacific. We propose that drying climate, coupled with documented social pressures and societal developments, instigated initial eastward exploration, resulting in SCI landfall(s) and return voyaging, with colonization a century or two later. This incremental settlement process likely involved the accumulation of critical maritime knowledge over several generations
Measurement of Decay and
Using a sample of 3.3 million Upsilon(4S) -> BBbar events collected with the
CLEO II detector at the Cornell Electron Storage Ring (CESR), we measure the
branching fraction for B -> rho l nu, |V_ub|, and the partial rate (Delta
Gamma) in three bins of q^2 = (p_B-p_rho)^2. We find B(B^0 -> rho^- l^+
nu)=(2.69 +- 0.41^+0.35_-0.40 +- 0.50) 10^-4, |V_ub|=(3.23 +- 0.24^+0.23_-0.26
+- 0.58) 10^-3, Delta Gamma (0 < q^2 < 7 GeV^2/c^4) =(7.6 +- 3.0 ^+0.9_-1.2 +-
3.0) 10^-2 ns^-1, Delta Gamma (7 < q^2 < 14 GeV^2/c^4) =(4.8 +- 2.9 ^+0.7_-0.8
+- 0.7) 10^-2 ns^-1, and Delta Gamma (14 < q^2 < 21 GeV^2/c^4) = (7.1 +-
2.1^+0.9_-1.1 +- 0.6)10^-2 ns^-1. The quoted errors are statistical,
systematic, and theoretical. The method is sensitive primarily to B -> rho l nu
decays with leptons in the energy range above 2.3 GeV. Averaging with the
previously published CLEO results, we obtain B(B^0 -> rho^- l^+ nu) = (2.57 +-
0.29^+0.33_-0.46 +- 0.41) 10^-4 and |V_{ub}| = (3.25 +- 0.14 ^+0.21_-0.29 +-
0.55) 10^-3.Comment: 35 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
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