1,458 research outputs found
A technique for automatic real time scoring of several simultaneous sleep electroencephalograms
Automatic real-time scoring of simultaneous sleep electroencephalogram
M-theory Compactifications on Manifolds with G2 Structure
In this paper we study M-theory compactifications on manifolds of G2
structure. By computing the gravitino mass term in four dimensions we derive
the general form for the superpotential which appears in such compactifications
and show that beside the normal flux term there is a term which appears only
for non-minimal G2 structure. We further apply these results to
compactifications on manifolds with weak G2 holonomy and make a couple of
statements regarding the deformation space of such manifolds. Finally we show
that the superpotential derived from fermionic terms leads to the potential
that can be derived from the explicit compactification, thus strengthening the
conjectures we make about the space of deformations of manifolds with weak G2
holonomy.Comment: 34 pages. Minor changes: typos corrected, references added. Version
to appear in Class. Quantum Gra
Vacuum Stability in Heterotic M-Theory
The problem of the stabilization of moduli is discussed within the context of
compactified strongly coupled heterotic string theory. It is shown that all
geometric, vector bundle and five-brane moduli are completely fixed, within a
phenomenologically acceptable range, by non-perturbative physics. This result
requires, in addition to the full space of moduli, non-vanishing Neveu-Schwarz
flux, gaugino condensation with threshold corrections and the explicit form of
the Pfaffians in string instanton superpotentials. The stable vacuum presented
here has a negative cosmological constant. The possibility of ``lifting'' this
to a metastable vacuum with positive cosmological constant is briefly
discussed.Comment: 39 pages, minor correction
Heterotic String Compactifications on Half-flat Manifolds II
In this paper, we continue the analysis of heterotic string compactifications
on half-flat mirror manifolds by including the 10-dimensional gauge fields. It
is argued, that the heterotic Bianchi identity is solved by a variant of the
standard embedding. Then, the resulting gauge group in four dimensions is still
E6 despite the fact that the Levi-Civita connection has SO(6) holonomy. We
derive the associated four-dimensional effective theories including matter
field terms for such compactifications. The results are also extended to more
general manifolds with SU(3) structure.Comment: 31 page
Stabilizing the Complex Structure in Heterotic Calabi-Yau Vacua
In this paper, we show that the presence of gauge fields in heterotic
Calabi-Yau compacitifications causes the stabilisation of some, or all, of the
complex structure moduli of the Calabi-Yau manifold while maintaining a
Minkowski vacuum. Certain deformations of the Calabi-Yau complex structure,
with all other moduli held fixed, can lead to the gauge bundle becoming
non-holomorphic and, hence, non-supersymmetric. This leads to an F-term
potential which stabilizes the corresponding complex structure moduli. We use
10- and 4-dimensional field theory arguments as well as a derivation based
purely on algebraic geometry to show that this picture is indeed correct. An
explicit example is presented in which a large subset of complex structure
moduli is fixed. We demonstrate that this type of theory can serve as the
hidden sector in heterotic vacua and can co-exist with realistic particle
physics.Comment: 17 pages, Late
A 3D track finder for the Belle II CDC L1 trigger
Machine learning methods are integrated into the pipelined first level (L1) track trigger of the upgraded flavor physics experiment Belle II at KEK in Tsukuba, Japan. The novel triggering techniques cope with the severe background from events outside the small collision region provided by the new SuperKEKB asymmetric-energy electron-positron collider. Using the precise drift-time information of the central drift chamber which provides axial and stereo wire layers, a neural network L1 trigger estimates the 3D track parameters of tracks, based on input from the axial wire planes provided by a 2D track finder. An extension of this 2D Hough track finder to a 3D finder is proposed, where the single hit representations in the Hough plane are trained using Monte Carlo. This 3D finder improves the track finding efficiency by including the stereo sense wires as input. The estimated polar track angle allows a specialization of the subsequent neural networks to sectors in the polar angle
Supersymmetric (non-)Abelian Bundles in the Type I and SO(32) Heterotic String
We discuss perturbative four-dimensional compactifications of both the SO(32)
heterotic and the Type I string on smooth Calabi-Yau manifolds endowed with
general non-abelian and abelian bundles. We analyse the generalized
Green-Schwarz mechanism for multiple anomalous U(1) factors and derive the
generically non-universal one-loop threshold corrections to the gauge kinetic
function as well as the one-loop corrected Fayet-Iliopoulos terms. The latter
can be interpreted as a stringy one-loop correction to the
Donaldson-Uhlenbeck-Yau condition. Applying S-duality, for the Type I string we
obtain the perturbative Pi-stability condition for non-abelian bundles on
curved spaces. Some simple examples are given, and we qualitatively discuss
some generic phenomenological aspects of this kind of string vacua. In
particular, we point out that in principle an intermediate string scale
scenario with TeV scale large extra dimensions might be possible for the
heterotic string.Comment: LaTeX, 32 pages, v2: refs adde
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