611 research outputs found
On Mirror Symmetry for Calabi-Yau Fourfolds with Three-Form Cohomology
We review the Kaluza-Klein reduction of Type IIA string theory on Calabi-Yau
fourfolds and apply mirror symmetry to the resulting two-dimensional effective theories. In the course of the reduction we focus
especially on non-trivial three-form cohomology on these fourfolds and
investigate the couplings of the corresponding massless zero-modes. These show
a dependence on both complex structure as well as K\"ahler structure
deformations and we provide evidence that they are determined by two
holomorphic functions that get exchanged via mirror symmetry. Application of
the mirror map enables us to give an explicit description of these functions at
the large volume and large complex structure point of the moduli space.Comment: Proceedings prepared for the "Workshop on Geometry and Physics",
November 2016, Ringberg Castle, Germany; 10 page
On Mirror Symmetry for Calabi-Yau Fourfolds with Three-Form Cohomology
We study the action of mirror symmetry on two-dimensional N=(2,2) effective
theories obtained by compactifying Type IIA string theory on Calabi-Yau
fourfolds. Our focus is on fourfold geometries with non-trivial three-form
cohomology. The couplings of the massless zero-modes arising by expanding in
these forms depend both on the complex structure deformations and the Kahler
structure deformations of the Calabi-Yau fourfold. We argue that two
holomorphic functions of the deformation moduli capture this information. These
are exchanged under mirror symmetry, which allows us to derive them at the
large complex structure and large volume point. We discuss the application of
the resulting explicit expression to F-theory compactifications and their weak
string coupling limit. In the latter orientifold settings we demonstrate
compatibility with mirror symmetry of Calabi-Yau threefolds at large complex
structure. As a byproduct we find an interesting relation of no-scale like
conditions on Kahler potentials to the existence of chiral and twisted-chiral
descriptions in two dimensions.Comment: 36 page
In-situ analysis of optically thick nanoparticle clouds
Nanoparticles grown in reactive plasmas and nanodusty plasmas gain high
interest from basic science and technology. One of the great challenges of
nanodusty plasmas is the in-situ diagnostic of the nanoparticle size and
refractive index. The analysis of scattered light by means of the Mie solution
of the Maxwell equations was proposed and used as an in-situ size diagnostic
during the past two decades. Today, imaging ellipsometry techniques and the
investigation of dense, i. e. optically thick nanoparticle clouds demand for
analysis methods to take multiple scattering into account. We present the first
3D Monte-Carlo polarized radiative transfer simulations of the scattered light
in a dense nanodusty plasma. This technique extends the existing diagnostic
methods for the in-situ analysis of the properties of nanoparticles to systems
where multiple scattering can not be neglected.Comment: 5 pages, 5 figure
Aspects of Calabi-Yau Fourfold Compactifications
The study of the geometry of Calabi-Yau fourfolds is relevant for
compactifications of string theory, M-theory, and F-theory to various
dimensions. In the first part of this thesis, we study the action of mirror
symmetry on two-dimensional \cN=(2,2) effective theories obtained by
compactifying Type IIA string theory on Calabi-Yau fourfolds. Our focus is on
fourfold geometries with non-trivial three-form cohomology. The couplings of
the massless zero-modes arising from an expansion of the three-form
gauge-potential into these forms depend both on the complex structure
deformations and the K\"ahler structure deformations of the Calabi-Yau
fourfold. We argue that two holomorphic functions, called three-form periods,
one for each kind of deformation, capture this information. These are exchanged
under mirror symmetry, which allows us to derive them at the large complex
structure and large volume point. We discuss the application of the resulting
explicit expression to F-theory compactifications and their weak string
coupling limit. The second part of this work introduces the mathematical
machinery to derive the complete moduli dependence of the periods of
non-trivial three-forms for fourfolds realized as hypersurfaces in toric
ambient spaces. It sets the stage to determine Picard-Fuchs-type differential
equations and integral expressions for these forms. The key tool is the
observation that non-trivial three-forms on fourfold hypersurfaces in toric
ambient spaces always stem from divisors that are build out of trees of toric
surfaces fibered over Riemann surfaces. The three-form periods are then
non-trivially related to the one-form periods of these Riemann surfaces. We
conclude with two explicit example fourfolds for F-theory compactifications %in
which the three-form periods determine axion decay constants.Comment: PhD Thesis, 178 page
Signal inference with unknown response: Calibration-uncertainty renormalized estimator
The calibration of a measurement device is crucial for every scientific
experiment, where a signal has to be inferred from data. We present CURE, the
calibration uncertainty renormalized estimator, to reconstruct a signal and
simultaneously the instrument's calibration from the same data without knowing
the exact calibration, but its covariance structure. The idea of CURE,
developed in the framework of information field theory, is starting with an
assumed calibration to successively include more and more portions of
calibration uncertainty into the signal inference equations and to absorb the
resulting corrections into renormalized signal (and calibration) solutions.
Thereby, the signal inference and calibration problem turns into solving a
single system of ordinary differential equations and can be identified with
common resummation techniques used in field theories. We verify CURE by
applying it to a simplistic toy example and compare it against existent
self-calibration schemes, Wiener filter solutions, and Markov Chain Monte Carlo
sampling. We conclude that the method is able to keep up in accuracy with the
best self-calibration methods and serves as a non-iterative alternative to it
All-sky reconstruction of the primordial scalar potential from WMAP temperature data
An essential quantity required to understand the physics of the early
Universe, in particular the inflationary epoch, is the primordial scalar
potential and its statistics. We present for the first time an all-sky
reconstruction of with corresponding -uncertainty from WMAP's
cosmic microwave background (CMB) temperature data -- a map of the very early
Universe right after the inflationary epoch. This has been achieved by applying
a Bayesian inference method that separates the whole inverse problem of the
reconstruction into many independent ones, each of them solved by an optimal
linear filter (Wiener filter). In this way, the three-dimensional potential
gets reconstructed slice by slice resulting in a thick shell of nested
spheres around the comoving distance to the last scattering surface. Each slice
represents the primordial scalar potential projected onto a sphere with
corresponding distance. Furthermore, we present an advanced method for
inferring and its power spectrum simultaneously from data, but argue
that applying it requires polarization data with high signal-to-noise levels
not available yet. Future CMB data should improve results significantly, as
polarization data will fill the present blind gaps of the
reconstruction
Cosmic expansion history from SNe Ia data via information field theory -- the charm code
We present charm (cosmic history agnostic reconstruction method), a novel
inference algorithm that reconstructs the cosmic expansion history as encoded
in the Hubble parameter from SNe Ia data. The novelty of the approach
lies in the usage of information field theory, a statistical field theory that
is very well suited for the construction of optimal signal recovery algorithms.
The charm algorithm infers non-parametrically
, the density evolution which
determines , without assuming an analytical form of but only
its smoothness with the scale factor . The inference problem of
recovering the signal from the data is formulated in a fully Bayesian
way. In detail, we have rewritten the signal as the sum of a background
cosmology and a perturbation. This allows us to determine the maximum a
posteriory estimate of the signal by an iterative Wiener filter method.
Applying charm to the Union2.1 supernova compilation, we have recovered a
cosmic expansion history that is fully compatible with the standard
CDM cosmological expansion history with parameter values consistent
with the results of the Planck mission
Site-resolved imaging of a fermionic Mott insulator
The complexity of quantum many-body systems originates from the interplay of
strong interactions, quantum statistics, and the large number of
quantum-mechanical degrees of freedom. Probing these systems on a microscopic
level with single-site resolution offers important insights. Here we report
site-resolved imaging of two-component fermionic Mott insulators, metals, and
band insulators using ultracold atoms in a square lattice. For strong repulsive
interactions we observe two-dimensional Mott insulators containing over 400
atoms. For intermediate interactions, we observe a coexistence of phases. From
comparison to theory we find trap-averaged entropies per particle of
. In the band-insulator we find local entropies as low as
. Access to local observables will aid the understanding
of fermionic many-body systems in regimes inaccessible by modern theoretical
methods.Comment: 6+7 page
Identification of pollen-expressed pectin methylesterase inhibitors in Arabidopsis
AbstractPectin methylesterases (PMEs) play an essential role during plant development by affecting the mechanical properties of the plant cell wall. Previous work indicated that plant PMEs may be subject to post-translational regulation. Here, we report the analysis of two proteinaceous inhibitors of PME in Arabidopsis thaliana (AtPMEI1 and 2). The functional analysis of recombinant AtPMEI1 and 2 proteins revealed that both proteins are able to inhibit PME activity from flowers and siliques. Quantitative RT-PCR analysis indicated that expression of AtPMEI1 and 2 mRNAs is tightly regulated during plant development with highest mRNA levels in flowers. Promotor::GUS fusions demonstrated that expression is mostly restricted to pollen
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