154 research outputs found
(Quantum) Space-Time as a Statistical Geometry of Fuzzy Lumps and the Connection with Random Metric Spaces
We develop a kind of pregeometry consisting of a web of overlapping fuzzy
lumps which interact with each other. The individual lumps are understood as
certain closely entangled subgraphs (cliques) in a dynamically evolving network
which, in a certain approximation, can be visualized as a time-dependent random
graph. This strand of ideas is merged with another one, deriving from ideas,
developed some time ago by Menger et al, that is, the concept of probabilistic-
or random metric spaces, representing a natural extension of the metrical
continuum into a more microscopic regime. It is our general goal to find a
better adapted geometric environment for the description of microphysics. In
this sense one may it also view as a dynamical randomisation of the causal-set
framework developed by e.g. Sorkin et al. In doing this we incorporate, as a
perhaps new aspect, various concepts from fuzzy set theory.Comment: 25 pages, Latex, no figures, some references added, some minor
changes added relating to previous wor
(Quantum) Space-Time as a Statistical Geometry of Lumps in Random Networks
In the following we undertake to describe how macroscopic space-time (or
rather, a microscopic protoform of it) is supposed to emerge as a
superstructure of a web of lumps in a stochastic discrete network structure. As
in preceding work (mentioned below), our analysis is based on the working
philosophy that both physics and the corresponding mathematics have to be
genuinely discrete on the primordial (Planck scale) level. This strategy is
concretely implemented in the form of \tit{cellular networks} and \tit{random
graphs}. One of our main themes is the development of the concept of
\tit{physical (proto)points} or \tit{lumps} as densely entangled subcomplexes
of the network and their respective web, establishing something like
\tit{(proto)causality}. It may perhaps be said that certain parts of our
programme are realisations of some early ideas of Menger and more recent ones
sketched by Smolin a couple of years ago. We briefly indicate how this
\tit{two-story-concept} of \tit{quantum} space-time can be used to encode the
(at least in our view) existing non-local aspects of quantum theory without
violating macroscopic space-time causality.Comment: 35 pages, Latex, under consideration by CQ
Insights into the room temperature magnetism of ZnO/Co3O4 mixtures
The origin of room temperature (RT) ferromagneticlike behavior in ZnO-based
diluted magnetic semiconductors is still an unclear topic. The present work
concentrates on the appearance of RT magnetic moments in just mixed ZnO/Co3O4
mixtures without thermal treatment. In this study, it is shown that the
magnetism seems to be related to surface reduction of the Co3O4 nanoparticles,
in which, an antiferromagnetic Co3O4 nanoparticle (core) is surrounded by a
CoO-like shell. This singular superficial magnetism has also been found in
other mixtures with semiconductors such as TiO2 and insulators such as Al2O3
Slow decay of dynamical correlation functions for nonequilibrium quantum states
A property of dynamical correlation functions for nonequilibrium states is
discussed. We consider arbitrary dimensional quantum spin systems with local
interaction and translationally invariant states with nonvanishing current over
them. A correlation function between local charge and local Hamiltonian at
different spacetime points is shown to exhibit slow decay.Comment: typos correcte
Planck Fluctuations, Measurement Uncertainties and the Holographic Principle
Starting from a critical analysis of recently reported surprisingly large
uncertainties in length and position measurements deduced within the framework
of quantum gravity, we embark on an investigation both of the correlation
structure of Planck scale fluctuations and the role the holographic hypothesis
is possibly playing in this context. While we prove the logical independence of
the fluctuation results and the holographic hypothesis (in contrast to some
recent statements in that direction) we show that by combining these two topics
one can draw quite strong and interesting conclusions about the fluctuation
structure and the microscopic dynamics on the Planck scale. We further argue
that these findings point to a possibly new and generalized form of quantum
statistical mechanics of strongly (anti)correlated systems of degrees of
freedom in this fundamental regime.Comment: 19 pages, Latex, no figures, some new references, to appear
ModPhysLett
Proper time and Minkowski structure on causal graphs
For causal graphs we propose a definition of proper time which for small
scales is based on the concept of volume, while for large scales the usual
definition of length is applied. The scale where the change from "volume" to
"length" occurs is related to the size of a dynamical clock and defines a
natural cut-off for this type of clock. By changing the cut-off volume we may
probe the geometry of the causal graph on different scales and therey define a
continuum limit. This provides an alternative to the standard coarse graining
procedures. For regular causal lattice (like e.g. the 2-dim. light-cone
lattice) this concept can be proven to lead to a Minkowski structure. An
illustrative example of this approach is provided by the breather solutions of
the Sine-Gordon model on a 2-dimensional light-cone lattice.Comment: 15 pages, 4 figure
Разработка методов тепловой дефектоскопии и дефектометрии авиационных композитов
Диссертация посвящена разработке методов дефектометрии в рамках импульсного теплового контроля авиационных композитов. Проведён сравнительный анализ существующих термографических методов количественной оценки глубины дефектов. Выявлены их преимущества и недостатки и обозначены существующие проблемы в этой сфере.
Представлен термографический метод количественной оценки глубины дефектов в материалах, обладающих свойством оптической полупрозрачности. Разработан метод количественной оценки глубины дефектов, характеризующихся малым отношением поперечных размеров к глубине. Разработан метод оценки толщины тонких покрытий основанный на пороговой отсечке кажущейся тепловой инерции.This study is focused on quantitative estimation of defect depth by applying pulsed thermal nondestructive testing. A novel method for estimating defect depth is proposed by taking into account the phenomenon of 3D heat diffusion finite lateral size of defects and thermal reflection coefficient at the boundary between a host material and defects. The method is based on the combination of a known analytical model and non-linear fitting (NLF) procedure. The apparent effusivity method for the quantitative evaluation of coating thickness in a one-sided thermal NDT procedure is presented. And the depth prediction method based on neural networks is presented
Relational interpretation of the wave function and a possible way around Bell's theorem
The famous ``spooky action at a distance'' in the EPR-szenario is shown to be
a local interaction, once entanglement is interpreted as a kind of ``nearest
neighbor'' relation among quantum systems. Furthermore, the wave function
itself is interpreted as encoding the ``nearest neighbor'' relations between a
quantum system and spatial points. This interpretation becomes natural, if we
view space and distance in terms of relations among spatial points. Therefore,
``position'' becomes a purely relational concept. This relational picture leads
to a new perspective onto the quantum mechanical formalism, where many of the
``weird'' aspects, like the particle-wave duality, the non-locality of
entanglement, or the ``mystery'' of the double-slit experiment, disappear.
Furthermore, this picture cirumvents the restrictions set by Bell's
inequalities, i.e., a possible (realistic) hidden variable theory based on
these concepts can be local and at the same time reproduce the results of
quantum mechanics.Comment: Accepted for publication in "International Journal of Theoretical
Physics
A new gas attenuator system for the ID17 biomedical beamline at the ESRF
Volume: 425Non peer reviewe
X-Tream: a novel dosimetry system for Synchrotron Microbeam Radiation Therapy
Microbeam Radiation Therapy (MRT) is a radiation treatment technique under development for inoperable brain tumors. MRT is based on the use of a synchrotron generated X-ray beam with an extremely high dose rate ( ~ 20 kGy/sec), striated into an array of X-ray micro-blades. In order to advance to clinical trials, a real-time dosimeter with excellent spatial resolution must be developed for absolute dosimetry. The design of a real-time dosimeter for such a radiation scenario represents a significant challenge due to the high photon flux and vertically striated radiation field, leading to very steep lateral dose gradients. This article analyses the striated radiation field in the context of the requirements for temporal dosimetric measurements and presents the architecture of a new dosimetry system based on the use of silicon detectors and fast data acquisition electronic interface. The combined system demonstrates micrometer spatial resolution and microsecond real time readout with accurate sensitivity and linearity over five orders of magnitude of input signal. The system will therefore be suitable patient treatment plan verification and may also be expanded for in-vivo beam monitoring for patient safety during the treatment
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