42 research outputs found
Observation of Sommerfeld precursors on a fluid surface
We report the observation of two types of Sommerfeld precursors (or
forerunners) on the surface of a layer of mercury. When the fluid depth
increases, we observe a transition between these two precursor surface waves in
good agreement with the predictions of asymptotic analysis. At depths thin
enough compared to the capillary length, high frequency precursors propagate
ahead of the ''main signal'' and their period and amplitude, measured at a
fixed point, increase in time. For larger depths, low frequency ''precursors''
follow the main signal with decreasing period and amplitude. These behaviors
are understood in the framework of the analysis first introduced for linear
transient electromagnetic waves in a dielectric medium by Sommerfeld and
Brillouin [1].Comment: to be published in Physical Review Letter
'Memory Must Be Defended': Beyond the Politics of Mnemonical Security
This article supplements and extends the ontological security theory in International Relations (IR) by conceptualizing the notion of mnemonical security. It engages critically the securitization of memory as a means of making certain historical remembrances secure by delegitimizing or outright criminalizing others. The securitization of historical memory by means of law tends to reproduce a sense of insecurity among the contesters of the ‘memory’ in question. To move beyond the politics of mnemonical security, two lines of action are outlined: (i) the ‘desecuritization’ of social remembrance in order to allow for its repoliticization, and (ii) the rethinking of the self–other relations in mnemonic conflicts. A radically democratic, agonistic politics of memory is called for that would avoid the knee-jerk reactive treatment of identity, memory and history as problems of security. Rather than trying to secure the unsecurable, a genuinely agonistic mnemonic pluralism would enable different interpretations of the past to be questioned, in place of pre-defining national or regional positions on legitimate remembrance in ontological security terms
Decay rate and renormalized frequency shift of a quantum wire Wannier exciton in a planar microcavity
The superradiant decay rate and frequency shift of a Wannier exciton in a
one-dimensional quantum wire are studied. It is shown that the dark mode
exciton can be examined experimentally when the quantum wire is embedded in a
planar microcavity. It is also found that the decay rate is greatly enhanced as
the cavity length is equal to the multiple wavelength of the emitted
photon. Similar to its decay rate counterpart, the frequency shift also shows
discontinuities at resonant modes.Comment: 12 pages, 2 figures. To appear in P. R. B. September 200
Narrowband Biphotons: Generation, Manipulation, and Applications
In this chapter, we review recent advances in generating narrowband biphotons
with long coherence time using spontaneous parametric interaction in monolithic
cavity with cluster effect as well as in cold atoms with electromagnetically
induced transparency. Engineering and manipulating the temporal waveforms of
these long biphotons provide efficient means for controlling light-matter
quantum interaction at the single-photon level. We also review recent
experiments using temporally long biphotons and single photons.Comment: to appear as a book chapter in a compilation "Engineering the
Atom-Photon Interaction" published by Springer in 2015, edited by A.
Predojevic and M. W. Mitchel