2,230 research outputs found
Short Range Interactions in the Hydrogen Atom
In calculating the energy corrections to the hydrogen levels we can identify
two different types of modifications of the Coulomb potential , with one
of them being the standard quantum electrodynamics corrections, ,
satisfying over the whole range of
the radial variable . The other possible addition to is a potential
arising due to the finite size of the atomic nucleus and as a matter of fact,
can be larger than in a very short range. We focus here on the latter
and show that the electric potential of the proton displays some undesirable
features. Among others, the energy content of the electric field associated
with this potential is very close to the threshold of pair production.
We contrast this large electric field of the Maxwell theory with one emerging
from the non-linear Euler-Heisenberg theory and show how in this theory the
short range electric field becomes smaller and is well below the pair
production threshold
The geometric tensor for classical states
We use the Liouville eigenfunctions to define a classical version of the
geometric tensor and study its relationship with the classical adiabatic gauge
potential (AGP). We focus on integrable systems and show that the imaginary
part of the geometric tensor is related to the Hannay curvature. The
singularities of the geometric tensor and the AGP allows us to link the
transition from Arnold-Liouville integrability to chaos with some of the
mathematical formalism of quantum phase transitions
The Schwinger action principle for classical systems
We use the Schwinger action principle to obtain the correct equations of
motion in the Koopman-von Neumann operational version of classical mechanics.
We restrict our analysis to non-dissipative systems and velocity-independent
forces. We show that the Schwinger action principle can be interpreted as a
variational principle in these special cases
Projective representation of the Galilei group for classical and quantum-classical systems
A physically relevant unitary irreducible non-projective representation of
the Galilei group is possible in the Koopman-von Neumann formulation of
classical mechanics. This classical representation is characterized by the
vanishing of the central charge of the Galilei algebra. This is in contrast to
the quantum case where the mass plays the role of the central charge. Here we
show, by direct construction, that classical mechanics also allows for a
projective representation of the Galilei group where the mass is the central
charge of the algebra. We extend the result to certain kind of
quantum-classical hybrid systems
Reconfigurable interconnects in DSM systems: a focus on context switch behavior
Recent advances in the development of reconfigurable optical interconnect technologies allow for the fabrication of low cost and run-time adaptable interconnects in large distributed shared-memory (DSM) multiprocessor machines. This can allow the use of adaptable interconnection networks that alleviate the huge bottleneck present due to the gap between the processing speed and the memory access time over the network. In this paper we have studied the scheduling of tasks by the kernel of the operating system (OS) and its influence on communication between the processing nodes of the system, focusing on the traffic generated just after a context switch. We aim to use these results as a basis to propose a potential reconfiguration of the network that could provide a significant speedup
Adiabatic driving and parallel transport for parameter-dependent Hamiltonians
We use the Van Vleck-Primas perturbation theory to study the problem of
parallel transport of the eigenvectors of a parameter-dependent Hamiltonian.
The perturbative approach allows us to define a non-Abelian connection
that generates parallel translation via unitary transformation of
the eigenvectors. It is shown that the connection obtained via the perturbative
approach is an average of the Maurer-Cartan 1-form of the one-parameter
subgroup generated by the Hamiltonian. We use the Yang-Mills curvature and the
non-Abelian Stokes' theorem to show that the holonomy of the connection
is related to the Berry phase
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