1,490 research outputs found
Absence of Ground States for a Class of Translation Invariant Models of Non-relativistic QED
We consider a class of translation invariant models of non-relativistic QED
with net charge. Under certain natural assumptions we prove that ground states
do not exist in the Fock space
Infraparticle Scattering States in Non-Relativistic QED: II. Mass Shell Properties
We study the infrared problem in the usual model of QED with non-relativistic
matter. We prove spectral and regularity properties characterizing the mass
shell of an electron and one-electron infraparticle states of this model. Our
results are crucial for the construction of infraparticle scattering states,
which are treated in a separate paper.Comment: AMS Latex, 45 pages, 2 figure
Diffuse radio emission in the complex merging galaxy cluster Abell 2069
Galaxy clusters with signs for a recent merger show in many cases extended
diffuse radio features. This emission originates from relativistic electrons
which suffer synchrotron losses due to the intra-cluster magnetic field. The
mechanisms of the particle acceleration and the properties of the magnetic
field are still poorly understood. We search for diffuse radio emission in
galaxy clusters. Here, we study the complex galaxy cluster Abell 2069, for
which X-ray observations indicate a recent merger. We investigate the cluster's
radio continuum emission by deep Westerbork Synthesis Radio Telescope (WSRT)
observations at 346 MHz and a Giant Metrewave Radio Telescope (GMRT)
observation at 322 MHz. We find an extended diffuse radio feature roughly
coinciding with the main component of the cluster. We classify this emission as
a radio halo and estimate its lower limit flux density to 25 +/- 9 mJy.
Moreover, we find a second extended diffuse source located at the cluster's
companion and estimate its flux density to 15 +/- 2 mJy. We speculate that this
is a small halo or a mini-halo. If true, this cluster is the first example of a
double-halo in a single galaxy cluster.Comment: 6 pages, 3 figures, accepted for publication in A&
Ionization of Atoms by Intense Laser Pulses
The process of ionization of a hydrogen atom by a short infrared laser pulse
is studied in the regime of very large pulse intensity, in the dipole
approximation. Let denote the integral of the electric field of the pulse
over time at the location of the atomic nucleus. It is shown that, in the limit
where , the ionization probability approaches unity and the
electron is ejected into a cone opening in the direction of and of
arbitrarily small opening angle. Asymptotics of various physical quantities in
is studied carefully. Our results are in qualitative agreement with
experimental data reported in \cite{1,2}.Comment: 27 pages, 1 figure
Contributions to the Fourth Solar Wind Conference
Recent results in interplanetary physics are examined. These include observations of shock waves and post-shock magnetic fields made by Voyager 1, 2; observations of the electron temperature as a function of distance between 1.36 AU and 2.25 AU; and observations of the structure of sector boundaries observed by Helios 1. A theory of electron energy transport in the collisionless solar wind is presented, and compared with observations. Alfven waves and Alvenic fluctuations in the solar wind are also discussed
Towards a construction of inclusive collision cross-sections in the massless Nelson model
The conventional approach to the infrared problem in perturbative quantum
electrodynamics relies on the concept of inclusive collision cross-sections. A
non-perturbative variant of this notion was introduced in algebraic quantum
field theory. Relying on these insights, we take first steps towards a
non-perturbative construction of inclusive collision cross-sections in the
massless Nelson model. We show that our proposal is consistent with the
standard scattering theory in the absence of the infrared problem and discuss
its status in the infrared-singular case.Comment: 23 pages, LaTeX. As appeared in Ann. Henri Poincar\'
Hyperfine splitting in non-relativistic QED: uniqueness of the dressed hydrogen atom ground state
We consider a free hydrogen atom composed of a spin-1/2 nucleus and a
spin-1/2 electron in the standard model of non-relativistic QED. We study the
Pauli-Fierz Hamiltonian associated with this system at a fixed total momentum.
For small enough values of the fine-structure constant, we prove that the
ground state is unique. This result reflects the hyperfine structure of the
hydrogen atom ground state.Comment: 22 pages, 3 figure
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First imaging of corotating interaction regions using the STEREO spacecraft
Plasma parcels are observed propagating from the Sun out to the large coronal heights monitored by the Heliospheric Imagers (HI) instruments onboard the NASA STEREO spacecraft during September 2007. The source region of these out-flowing parcels is found to corotate with the Sun and to be rooted near the western boundary of an equatorial coronal hole. These plasma enhancements evolve during their propagation through the HI cameras’ fields of view and only becoming fully developed in the outer camera field of view. We provide evidence that HI is observing the formation of a Corotating Interaction Region(CIR) where fast solar wind from the equatorial coronal hole is interacting with the slow solar wind of the streamer belt located on the western edge of that coronal hole. A dense plasma parcel is also observed near the footpoint of the observed CIR at a distance less than 0.1AU from the Sun where fast wind would have not had time to catch up slow wind. We suggest that this low-lying plasma enhancement is a plasma parcel which has been disconnected from a helmet streamer and subsequently becomes embedded inside the corotating interaction region
On the Atomic Photoeffect in Non-relativistic QED
In this paper we present a mathematical analysis of the photoelectric effect
for one-electron atoms in the framework of non-relativistic QED. We treat
photo-ionization as a scattering process where in the remote past an atom in
its ground state is targeted by one or several photons, while in the distant
future the atom is ionized and the electron escapes to spacial infinity. Our
main result shows that the ionization probability, to leading order in the
fine-structure constant, , is correctly given by formal time-dependent
perturbation theory, and, moreover, that the dipole approximation produces an
error of only sub-leading order in . In this sense, the dipole
approximation is rigorously justified.Comment: 25 page
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