349 research outputs found

### Compactified NCOS and duality

We study four-dimensional U(1) on a non-commutative T^2 with rational Theta.
This theory has dual descriptions as ordinary SYM or as NCOS. We identify a set
of massive non-interacting KK states in the SYM theory and track them through
the various dualities. They appear as stretched strings in the non-commutative
U(1) providing another example of the IR/UV mixing in non-commutative field
theories. In the NCOS these states appear as D-strings with winding and
momentum. They form an unconventional type of 1/4 BPS state with the 3-brane.
To obtain a consistent picture of S-duality for compactified theories it is
essential to keep track of both the NS and the RR B-fields.Comment: 16 pages, references correcte

### Thick domain walls and singular spaces

We discuss thick domain walls interpolating between spaces with naked
singularities and give arguments based on the $AdS$/CFT correspondence why such
singularities may be physically meaningful. Our examples include thick domain
walls with Minkowski, de Sitter, and anti-de Sitter geometries on the
four-dimensional slice. For flat domain walls we can solve the equivalent
quantum mechanics problem exactly, which provides the spectrum of graviton
states. In one of the examples we discuss, the continuum states have a mass
gap. We compare the graviton spectra with expectations from the $AdS$/CFT
correspondence and find qualitative agreement. We also discuss unitary boundary
conditions and show that they project out all continuum states.Comment: 21 pages, v2: references corrected, v3: minor corrections in sect.

### Mirror symmetry for N=1 QED in three dimensions

We construct three-dimensional N=1 QED with N_f flavors using branes of type
IIB string theory. This theory has a mirror, which can be realized using the
S-dual brane configuration. As in examples with more supersymmetry, the Higgs
branch of the original theory gets mapped into the Coulomb branch of the
mirror. We use parity invariance to argue that these branches cannot be lifted
by quantum corrections.Comment: 10 pages, Latex, 1 figure, reference adde

### Heterotic Little String Theories and Holography

It has been conjectured that Little String Theories in six dimensions are
holographic to critical string theory in a linear dilaton background. We test
this conjecture for theories arising on the worldvolume of heterotic
fivebranes. We compute the spectrum of chiral primaries in these theories and
compare with results following from Type I-heterotic duality and the AdS/CFT
correspondence. We also construct holographic duals for heterotic fivebranes
near orbifold singularities. Finally we find several new Little String Theories
which have Spin(32)/Z_2 or E_8 \times E_8 global symmetry but do not have a
simple interpretation either in heterotic or M-theory.Comment: 27 pages, LaTe

### Impacts of the German interurban bus market deregulation on regional railway services

Since 1 January 2013, the German interurban bus market is deregulated. As a consequence of deregulation, the number of interurban bus passengers has increased from 2.5 million in 2012 to 24 million in 2016. Today there is a dense interurban bus network covering the whole German territory. In parallel to the interurban bus network, which is operated mostly by private companies, there is a network of regional railway services that is subsidized by public funds. In order to prevent cannibalization of regional railway services, interurban bus companies are allowed to offer their services only where the distance between two cities is at least 50 kilometres and the regional train takes at least one hour. Despite these restrictions, there is still competition between the two modes of transportation. The present paper gives some insight into the intermodal competition between interurban buses and regional railways as well as into the financial impact of the new interurban bus market on the regional railway market. For this purpose, we have combined regional railway, geographical and interurban bus data. Our estimation shows that the financial impact of interurban bus competition on the entire regional railway system is relatively low.Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne

### A Simple Volcano Potential with an Analytic, Zero-Energy, Ground State

We describe a simple volcano potential, which is supersymmetric and has an
analytic, zero-energy, ground state. (The KK modes are also analytic.) It is an
interior harmonic oscillator potential properly matched to an exterior angular
momentum-like tail. Special cases are given to elucidate the physics, which may
be intuitively useful in studies of higher-dimensional gravity.Comment: 8 pages, 3 figure

### Perturbative Corrections to a Sum Rule for the Heavy Quark Kinetic Energy

We calculate the perturbative corrections to order \alpha_s^2\beta_0 to the
sum rule derived from the second moment of the time-ordered product of b \to c
currents near zero recoil. This sum rule yields a bound on \lambda_1, the
expectation value of the b quark kinetic energy operator inside the B meson.
The perturbative corrections significantly weaken the bound relative to the
tree level result, yielding \lambda_1 < -0.15 GeV^2.Comment: 10 pages revtex, uses FEYNMA

### Order 1/m_b^3 corrections to B\to X_c\ell\bar\nu decay and their implication for the measurement of \bar\Lambda and \lambda_1

We compute the order 1/m_b^3 nonperturbative contributions to the inclusive
differential B\to X_c\ell\bar\nu decay rate. They are parametrized by the
expectation values of two local and four nonlocal dimension-six operators. We
use our results to estimate part of the theoretical uncertainties in the
extraction of matrix elements \bar\Lambda and \lambda_1 from the lepton
spectrum in the inclusive semileptonic B decay and find them to be very large.
We also compute the 1/m_b^3 corrections to the moments of the hadronic
invariant mass spectrum in this decay, and combine them with the extracted
values of \bar\Lambda and \lambda_1 to put an upper bound on the branching
fraction Br(B\to D^{**}\ell\bar\nu).Comment: 21 pages, revtex, 2 postscript figures. Section on the
nonrelativistic quark model estimates is removed; some points of the
computation are clarified; results unchange

- â€¦