Search results for " Bundle"
showing 10 items of 217 documents
Nucleus incertus—An emerging modulatory role in arousal, stress and memory
2011
A major challenge in systems neuroscience is to determine the underlying neural circuitry and associated neurotransmitters and receptors involved in psychiatric disorders, such as anxiety and depression. A focus of many of these studies has been specific brainstem nuclei that modulate levels of arousal via their ascending monoaminergic projections (e.g. the serotonergic dorsal raphe, noradrenergic locus ceruleus and cholinergic laterodorsal tegmental nucleus). After years of relative neglect, the subject of recent studies in this context has been the GABAergic nucleus incertus,1 which is located in the midline periventricular central gray in the ‘prepontine’ hindbrain, with broad projection…
The effect of rewarding hypothalamic stimulation on behavioral and neural hippocampal responses during trace eyeblink conditioning in rabbit (Oryctol…
2005
Rabbits were trace-conditioned with a tone as a conditioned stimulus and an airpuff as an unconditioned stimulus. Electrical stimulation to the medial forebrain bundle in the lateral hypothalamus was delivered either before or after the tone-airpuff pair. The purpose of the present study was to test whether the effect of post-trial hypothalamic stimulation differed from the effect of pre-trial hypothalamic stimulation on trace conditioning in the same subjects. Additionally, hippocampal responses were measured during sessions to see if hypothalamic stimulation activated dopaminergic fibres and affected hippocampal cell functioning and thus learning. The results showed that behavioral nictit…
Normal Coulomb Frames in $${\mathbb{R}}^{4}$$
2012
Now we consider two-dimensional surfaces immersed in Euclidean spaces \({\mathbb{R}}^{n+2}\) of arbitrary dimension. The construction of normal Coulomb frames turns out to be more intricate and requires a profound analysis of nonlinear elliptic systems in two variables. The Euler–Lagrange equations of the functional of total torsion are identified as non-linear elliptic systems with quadratic growth in the gradient, and, more exactly, the nonlinearity in the gradient is of so-called curl-type, while the Euler–Lagrange equations appear in a div-curl-form. We discuss the interplay between curvatures of the normal bundles and torsion properties of normal Coulomb frames. It turns out that such …
Uniform fibre Bragg gratings with an embedded perturbed section for multiple applications
1999
The interest in fibre Bragg gratings has been increased with the development of flexible fabrication techniques which are able to make gratings with any non-uniform characteristic (chirped, apodised, sampled, phase-shifted, etc.) required for an specific application [1].
On the volume of unit vector fields on spaces of constant sectional curvature
2004
A unit vector field X on a Riemannian manifold determines a submanifold in the unit tangent bundle. The volume of X is the volume of this submanifold for the induced Sasaki metric. It is known that the parallel fields are the trivial minima.
Purification of Lindblad dynamics, geometry of mixed states and geometric phases
2015
We propose a nonlinear Schr\"odinger equation in a Hilbert space enlarged with an ancilla such that the partial trace of its solution obeys to the Lindblad equation of an open quantum system. The dynamics involved by this nonlinear Schr\"odinger equation constitutes then a purification of the Lindbladian dynamics. This nonlinear equation is compared with other Schr\"odinger like equations appearing in the theory of open systems. We study the (non adiabatic) geometric phases involved by this purification and show that our theory unifies several definitions of geometric phases for open systems which have been previously proposed. We study the geometry involved by this purification and show th…
Presymplectic manifolds and conservation laws
2008
In this paper we make use of a new structure called seeded fibre bundle. This allows us to combine the symplectic formalism and general relativity. A theorem of existence is obtained and some examples and properties are studied.
One-Loop Effective Lagrangian in QED
2020
Our main goal in this section is the derivation of an expression for the effective Lagrangian in one-loop approximation. So let’s start with the vacuum persistence amplitude in presence of an external field: $$\displaystyle \langle 0_+\vert 0_-\rangle ^A = e^{ iW^{(1)}[A]} = e^{i \int d^4x\mathcal {L}^{(1)}(x)} $$
Nonlinear Evolution Equations, Quasi-Solitons and their Experimental Manifestation
1990
We review the typical experimental facts which characterize quasisolitons in one-dimensional real systems, in connection with their modeling by nonlinear partial differential equations.We consider these nonlinear waves or excitations in two different domains of the real world : the macroworld and the microworld. In the macroworld we examine typical one-dimensional devices : the electrical networks, the Josephson transmission lines and the optical fibers, where the localized waves or pulses can be simply and coherently created, easily observed and manipulated on a macroscopic scale. In the microworld, we consider the magnetic chains and polymers, where the indirect experimental signatures of…
Covariant phase space quantization of the Jackiw-Teitelboim model of two-dimensional gravity
1992
Abstract On the basis of the covariant phase space formulation of field theory we analyze the Jackiw-Teitelboim model of two-dimensional gravity on a cylinder. We compute explicitly the symplectic structure showing that the (reduced) phase space is the cotangent bundle of the space of conjugacy classes of the PSL(2, R ) group. This makes it possible to quantize the theory exactly. The Hilbert space is given by the character functions of the PSL (2, R ) group. As a byproduct, this implies the complete equivalence with the PSL (2, R )-topological gravity model.