11,617 research outputs found
Bypassing the bandwidth theorem with PT symmetry
The beat time {\tau}_{fpt} associated with the energy transfer between two
coupled oscillators is dictated by the bandwidth theorem which sets a lower
bound {\tau}_{fpt}\sim 1/{\delta}{\omega}. We show, both experimentally and
theoretically, that two coupled active LRC electrical oscillators with
parity-time (PT) symmetry, bypass the lower bound imposed by the bandwidth
theorem, reducing the beat time to zero while retaining a real valued spectrum
and fixed eigenfrequency difference {\delta}{\omega}. Our results foster new
design strategies which lead to (stable) pseudo-unitary wave evolution, and may
allow for ultrafast computation, telecommunication, and signal processing.Comment: 5 pages, 3 figure
Arctic Ecology: A Decade of Experience
A quick glance at the title of this presentation and the reader braces himself for another antipollution or “save-the-sod” type of discourse that has become so popular these days. I do not wish to detract from the importance or the need for such efforts but I would like to address myself to the the broader meaning of the term.
Ecology--the word comes from the Greek root “oikos” which means house or household. What I’d like to do is to tell you about this “house” I’ve been living in for the past 10 years
Abell 754: A Non-Head On Collision of Subclusters
We have analyzed spatially resolved spectra of A754 obtained with ASCA. The
combination of spectral and imaging capabilities of ASCA has set unprecedented
constraints on the hydrodynamical effects of a cluster merger. We find
significant gas temperature variations over the cluster face, indicating shock
heating of the atmosphere during the merger. The hottest region, >12 keV, is
located in the region of the Northwest galaxy clump though the entire region
along the cluster axis appears to be hotter than the mean cluster temperature
(~9 keV). The cool, ~5 keV gas originally found with the HEAO1-A2 experiment,
resides in the exterior of the cluster atmosphere and in plume of gas we
identify with a stripped cool atmosphere of the infalling subcluster. We have
also attempted to reconstruct an iron abundance map of this merging system.
Though poorly constrained, no significant deviations of abundance from the mean
value are apparent in the individual regions.
A754 is the only cluster so far which shows the significant temperature
pattern expected in a subcluster merger, in both the ROSAT (Henry & Briel 1995)
and ASCA data, providing the first possibility to compare it with theoretical
predictions. The observed temperature and surface brightness maps suggest that
the two colliding subunits have missed each other by about 1 Mpc, and are now
moving perpendicular to the cluster axis in the image plane (as, e.g., in the
simulations by Evrard etal 1996).Comment: Latex, 10 pages, 3 figures incl. color plate, uses aaspp4.sty,
flushrt.sty and pstricks.sty. Submitted to ApJ Letter
Magnetic flux response of non-Hermitian topological phases
We derive the response of non-Hermitian topological phases with intrinsic point gap topology to localized magnetic flux insertions. In two spatial dimensions, we identify the necessary and sufficient conditions for a flux skin effect that localizes an extensive number of in-gap modes at a flux core. In three dimensions, we furthermore establish the existence of: a flux spectral jump, where flux tube insertion fills up the entire point gap only at a single parallel crystal momentum; a higher-order flux skin effect, which occurs at the ends of flux tubes in presence of pseudo-inversion symmetry; and a flux Majorana mode that represents a spectrally isolated mid-gap state in the complex energy plane. We uniquely associate each non-Hermitian symmetry class with intrinsic point gap topology with one of these cases or a trivial flux response, and discuss possible experimental realizations
Functional fat injection in the treatment of dysphagia following surgery
Functional fat injection under local anesthesia could be useful in the treatment of chronic dysphagia in selected patients with tissue loss secondary to laryngeal surgery
High magnetic field superconducting properties of Nb3Sn films Final report
High magnetic field superconducting properties of niobium stannide films and shielding characterictics of stannide layer
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