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 $L_{c}$ 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