12,856 research outputs found
Localization of Eigenfunctions in the Stadium Billiard
We present a systematic survey of scarring and symmetry effects in the
stadium billiard. The localization of individual eigenfunctions in Husimi phase
space is studied first, and it is demonstrated that on average there is more
localization than can be accounted for on the basis of random-matrix theory,
even after removal of bouncing-ball states and visible scars. A major point of
the paper is that symmetry considerations, including parity and time-reversal
symmetries, enter to influence the total amount of localization. The properties
of the local density of states spectrum are also investigated, as a function of
phase space location. Aside from the bouncing-ball region of phase space,
excess localization of the spectrum is found on short periodic orbits and along
certain symmetry-related lines; the origin of all these sources of localization
is discussed quantitatively and comparison is made with analytical predictions.
Scarring is observed to be present in all the energy ranges considered. In
light of these results the excess localization in individual eigenstates is
interpreted as being primarily due to symmetry effects; another source of
excess localization, scarring by multiple unstable periodic orbits, is smaller
by a factor of .Comment: 31 pages, including 10 figure
Intertwining technique for a system of difference Schroedinger equations and new exactly solvable multichannel potentials
The intertwining operator technique is applied to difference Schroedinger
equations with operator-valued coefficients. It is shown that these equations
appear naturally when a discrete basis is used for solving a multichannel
Schroedinger equation. New families of exactly solvable multichannel
Hamiltonians are found
Shifting Bordering and Rescue Practices in the Central Mediterranean Sea, October 2013âOctober 2015
This counterâmapping project illustrates the areas of intervention of different operations geared toward rescue and enforcement between 2013 and 2015, including the Italian Navy's âMare Nostrumâ search and rescue mission, the EU border agency Frontex's âTritonâ enforcement operation, the humanitarian interventions of commercial vessels, and the action of civilâsociety rescue vessels such as those operated by MĂ©decins Sans FrontiĂšres (MSFâDoctors Without Borders). The project offers a spatial understanding of the Mediterranean borderâscape, the practices of rescue and enforcement that occur within it, and the risk of seaâcrossing at this particular moment. Through these maps, the Central Mediterranean Sea emerges as a striking laboratory from which novel legal arrangements, surveillance technologies, and institutional assemblages converge
Shifting Bordering and Rescue Practices in the Central Mediterranean Sea, October 2013-October 2015
This counterâmapping project illustrates the areas of intervention of different operations geared toward rescue and enforcement between 2013 and 2015, including the Italian Navy's âMare Nostrumâ search and rescue mission, the EU border agency Frontex's âTritonâ enforcement operation, the humanitarian interventions of commercial vessels, and the action of civilâsociety rescue vessels such as those operated by MĂ©decins Sans FrontiĂšres (MSFâDoctors Without Borders). The project offers a spatial understanding of the Mediterranean borderâscape, the practices of rescue and enforcement that occur within it, and the risk of seaâcrossing at this particular moment. Through these maps, the Central Mediterranean Sea emerges as a striking laboratory from which novel legal arrangements, surveillance technologies, and institutional assemblages converge
Beyond the First Recurrence in Scar Phenomena
The scarring effect of short unstable periodic orbits up to times of the
order of the first recurrence is well understood. Much less is known, however,
about what happens past this short-time limit. By considering the evolution of
a dynamically averaged wave packet, we show that the dynamics for longer times
is controlled by only a few related short periodic orbits and their interplay.Comment: 4 pages, 4 Postscript figures, submitted to Phys. Rev. Let
Influence of diffraction on the spectrum and wavefunctions of an open system
In this paper, we demonstrate the existence and significance of diffractive
orbits in an open microwave billiard, both experimentally and theoretically.
Orbits that diffract off of a sharp edge of the system are found to have a
strong influence on the transmission spectrum of the system, especially in the
regime where there are no stable classical orbits. On resonance, the
wavefunctions are influenced by both classical and diffractive orbits. Off
resonance, the wavefunctions are determined by the constructive interference of
multiple transient, nonperiodic orbits. Experimental, numerical, and
semiclassical results are presented.Comment: 27 pages, 29 figures, and 3 tables. Submitted to Physical Review E. A
copy with higher resolution figures is available at
http://monsoon.harvard.edu/~hersch/papers.htm
Vortices and confinement at weak coupling
We discuss the physical picture of thick vortices as the mechanism
responsible for confinement at arbitrarily weak coupling in SU(2) gauge theory.
By introducing appropriate variables on the lattice we distinguish between
thin, thick and `hybrid' vortices, the latter involving Z(2) monopole loop
boundaries. We present numerical lattice simulation results that demonstrate
that the full SU(2) string tension at weak coupling arises from the presence of
vortices linked to the Wilson loop. Conversely, excluding linked vortices
eliminates the confining potential. The numerical results are stable under
alternate choice of lattice action as well as a smoothing procedure which
removes short distance fluctuations while preserving long distance physics.Comment: 21 pages, LaTe
Probing the Region of Massless Quarks in Quenched Lattice QCD using Wilson Fermions
We study the spectrum of with being the
Wilson-Dirac operator on the lattice with bare mass equal to . The
background gauge fields are generated using the SU(3) Wilson action at
on an lattice. We find evidence that the spectrum of
is gapless for , implying that the physical quark is
massless in this whole region.Comment: 22 pages, LaTeX file, uses elsart.sty, includes 11 figures A
typographical error in one reference has been fixe
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