2,083 research outputs found
Tunneling in Polymer Quantization and the Quantum Zeno Effect
As an application of the polymer quantization scheme, in this work we
investigate the one dimensional quantum mechanical tunneling phenomenon from
the perspective of polymer representation of a non-relativistic point particle
and derive the transmission and reflection coefficients. Since any tunneling
phenomenon inevitably evokes a tunneling time we attempt an analytical
calculation of tunneling times by defining an operator well suited in discrete
spatial geometry. The results that we come up with hint at appearance of the
Quantum Zeno Effect in polymer framework.Comment: 21pp,3 figures, to be published in Phys. Lett.
Relativistic MOND from Modified Energetics
We begin to investigate the question of what modifications in energy-momentum
tensor can yield correct MOND regime. As a starting study, we refrain from
insisting on an action principle and focus exclusively on the equations of
motion. The present work, despite the absence of an explicit action functional,
can be regarded to extend Milgrom's modified inertia approach to relativistic
domain. Our results show that a proper MOND limit arises if energy-momentum
tensor is modified to involve determinant of the metric tensor in reference to
the flat metric, where the latter is dynamically generated as in gravitational
Higgs mechanism. This modified energy-momentum tensor is conserved in both
Newtonian and MONDian regimes.Comment: 7p
Time-Frequency Warped Waveforms
The forthcoming communication systems are advancing towards improved
flexibility in various aspects. Improved flexibility is crucial to cater
diverse service requirements. This letter proposes a novel waveform design
scheme that exploits axis warping to enable peaceful coexistence of different
pulse shapes. A warping transform manipulates the lattice samples non-uniformly
and provides flexibility to handle the time-frequency occupancy of a signal.
The proposed approach enables the utilization of flexible pulse shapes in a
quasi-orthogonal manner and increases the spectral efficiency. In addition, the
rectangular resource block structure, which assists an efficient resource
allocation, is preserved with the warped waveform design as well.Comment: 4 pages, 5 figures; accepted version (The URL for the final version:
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8540914&isnumber=8605392
Eine rechtssoziologische Analyse des islamischen waqf-Systems
Je abstrakter eine Rechtsnorm gefasst ist, desto besser kann sie den durch die funktionale Differenzierung der Gesellschaft entstandenen Kontingenzen gerecht werden. Umgekehrt hemmt ein Rechtssystem die System- und Sozialintegration einer Gesellschaft, wenn es hauptsächlich mit Analogien arbeitet, materielle Ziele verfolgt und damit den notwendigen Formwandel verhindert. Ein gutes Beispiel dafür ist das islamische waqf-System. Im Frühislam war Solidarität durch freiwillige Wohltätigkeit im zakāt-System erwünscht. In der Expansionsphase der islamischen Herrschaft wurde die Freiwilligkeit in eine theologisch legitimierte Norm verwandelt und im waqf-System institutionalisiert. Während dieser Transformationsphase dienten awqāf als ein System von Kompromissen. Dabei wurden die Bedingungen für waqf-Gründungen vom Zentrum bestimmt und ihre Verwaltung der Peripherie überlassen. Diese Arbeitsteilung wurde im Osmanischen Reich durch das duale Rechtssystem von sakralem und sultanischem Ursprung zusammengehalten. Zugleich wurde während dieser Phase die Lebenswelt einer rationalen Reflexion und das Recht einer Positivierung unterzogen. Die Stadien dieser Evolution werden im Folgenden nachgezeichnet und kritisch bewertet
Higgsed Stueckelberg Vector and Higgs Quadratic Divergence
Here we show that, a hidden vector field whose gauge invariance is ensured by
a Stueckelberg scalar and whose mass is spontaneously generated by the Standard
Model Higgs field contributes to quadratic divergences in the Higgs boson mass
squared, and even leads to its cancellation at one-loop when Higgs coupling to
gauge field is fine-tuned. In contrast to mechanisms based on hidden scalars
where a complete cancellation cannot be achieved, stabilization here is
complete in that the hidden vector and the accompanying Stueckelberg scalar are
both free from quadratic divergences at one-loop. This stability, deriving from
hidden exact gauge invariance, can have important implications for modelling
dark phenomena like dark matter, dark energy, dark photon and neutrino masses.
The hidden fields can be produced at the LHC.Comment: 5pp, 1 fig. Improved exposition, rectified concurrency to broken and
unbroken electroweak vacua, added reference
Anatomical landmark based registration of contrast enhanced T1-weighted MR images
In many problems involving multiple image analysis, an im- age registration step is required. One such problem appears in brain tumor imaging, where baseline and follow-up image volumes from a tu- mor patient are often to-be compared. Nature of the registration for a change detection problem in brain tumor growth analysis is usually rigid or affine. Contrast enhanced T1-weighted MR images are widely used in clinical practice for monitoring brain tumors. Over this modality, con- tours of the active tumor cells and whole tumor borders and margins are visually enhanced. In this study, a new technique to register serial contrast enhanced T1 weighted MR images is presented. The proposed fully-automated method is based on five anatomical landmarks: eye balls, nose, confluence of sagittal sinus, and apex of superior sagittal sinus. Af- ter extraction of anatomical landmarks from fixed and moving volumes, an affine transformation is estimated by minimizing the sum of squared distances between the landmark coordinates. Final result is refined with a surface registration, which is based on head masks confined to the sur- face of the scalp, as well as to a plane constructed from three of the extracted features. The overall registration is not intensity based, and it depends only on the invariant structures. Validation studies using both synthetically transformed MRI data, and real MRI scans, which included several markers over the head of the patient were performed. In addition, comparison studies against manual landmarks marked by a radiologist, as well as against the results obtained from a typical mutual information based method were carried out to demonstrate the effectiveness of the proposed method
Waveform Design for 5G and Beyond
5G is envisioned to improve major key performance indicators (KPIs), such as
peak data rate, spectral efficiency, power consumption, complexity, connection
density, latency, and mobility. This chapter aims to provide a complete picture
of the ongoing 5G waveform discussions and overviews the major candidates. It
provides a brief description of the waveform and reveals the 5G use cases and
waveform design requirements. The chapter presents the main features of cyclic
prefix-orthogonal frequency-division multiplexing (CP-OFDM) that is deployed in
4G LTE systems. CP-OFDM is the baseline of the 5G waveform discussions since
the performance of a new waveform is usually compared with it. The chapter
examines the essential characteristics of the major waveform candidates along
with the related advantages and disadvantages. It summarizes and compares the
key features of different waveforms.Comment: 22 pages, 21 figures, 2 tables; accepted version (The URL for the
final version:
https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119333142.ch2
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