8,513 research outputs found
Solutions without singularities in gauge theory of gravitation
A de-Sitter gauge theory of the gravitational field is developed using a
spherical symmetric Minkowski space-time as base manifold. The gravitational
field is described by gauge potentials and the mathematical structure of the
underlying space-time is not affected by physical events. The field equations
are written and their solutions without singularities are obtained by imposing
some constraints on the invariants of the model. An example of such a solution
is given and its dependence on the cosmological constant is studied. A
comparison with results obtained in General Relativity theory is also
presented.
Keywords: gauge theory, gravitation, singularity, computer algebraComment: 9 pages, no figure
Elementary Particles and Spin Representations
We emphasize that the group-theoretical considerations leading to SO(10)
unification of electro-weak and strong matter field components naturally extend
to space-time components, providing a truly unified description of all
generation degrees of freedoms in terms of a single chiral spin representation
of one of the groups SO(13,1), SO(9,5), SO(7,7) or SO(3,11). The realization of
these groups as higher dimensional space-time symmetries produces unification
of all fundamental fermions is a single space-time spinor.Comment: 4 page
From Crystalline to Amorphous Germania Bilayer Films at the Atomic Scale: Preparation and Characterization
A new two-dimensional (2D) germanium dioxide film has been prepared. The film consists of interconnected germania tetrahedral units forming a bilayer structure, weakly coupled to the supporting Pt(111) metal-substrate. Density functional theory calculations predict a stable structure of 558-membered rings for germania films, while for silica films 6-membered rings are preferred. By varying the preparation conditions the degree of order in the germania films is tuned. Crystalline, intermediate ordered and purely amorphous film structures are resolved by analysing scanning tunnelling microscopy images
SUGRA Noether Charges
In this work a generic set of boundary conditions for SUGRA
is proposed. This conditions defines that Hamiltonian charges equals Noether
ones, including supercharge
From Crystalline to Amorphous Germania Bilayer Films at the Atomic Scale: Preparation and Characterization
A new two-dimensional (2D) germanium dioxide film has been prepared. The film consists of interconnected germania tetrahedral units forming a bilayer structure, weakly coupled to the supporting Pt(111) metal-substrate. Density functional theory calculations predict a stable structure of 558-membered rings for germania films, while for silica films 6-membered rings are preferred. By varying the preparation conditions the degree of order in the germania films is tuned. Crystalline, intermediate ordered and purely amorphous film structures are resolved by analysing scanning tunnelling microscopy images
Phase locking below rate threshold in noisy model neurons
The property of a neuron to phase-lock to an oscillatory stimulus before adapting its spike rate to the stimulus frequency plays an important role for the auditory system. We investigate under which conditions neurons exhibit this phase locking below rate threshold. To this end, we simulate neurons employing the widely used leaky integrate-and-fire (LIF) model. Tuning parameters, we can arrange either an irregular spontaneous or a tonic spiking mode. When the neuron is stimulated in both modes, a significant rise of vector strength prior to a noticeable change of the spike rate can be observed. Combining analytic reasoning with numerical simulations, we trace this observation back to a modulation of interspike intervals, which itself requires spikes to be only loosely coupled. We test the limits of this conception by simulating an LIF model with threshold fatigue, which generates pronounced anticorrelations between subsequent interspike intervals. In addition we evaluate the LIF response for harmonic stimuli of various frequencies and discuss the extension to more complex stimuli. It seems that phase locking below rate threshold occurs generically for all zero mean stimuli. Finally, we discuss our findings in the context of stimulus detection
On non- solutions to the Seiberg-Witten equations
We show that a previous paper of Freund describing a solution to the
Seiberg-Witten equations has a sign error rendering it a solution to a related
but different set of equations. The non- nature of Freund's solution is
discussed and clarified and we also construct a whole class of solutions to the
Seiberg-Witten equations.Comment: 8 pages, Te
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