961 research outputs found
Bare LO-Phonon Peak in THz-Emission Signals: a Dielectric-Function Analysis
We present a normal-mode analysis of coupled photocarrier-phonon dynamics in
Te. We consider a dielectric function which accounts for LO phonons and the
electron-hole gas within the Debye-Huckel model and RPA. Our main finding is
the existence of a bare LO phonon mode in the system even at high carrier
density. This oscillation is an unscreened L- mode arising from ineffective
screening at large wave vectors. This mode is consistent with the bare
LO-phonon peak in recent THz-emission spectra of Te.Comment: 3 pages, 1 figure, Special Issue: Proceedings of the 10th Brazilian
Workshop on Semiconductor Physics, Guaruja/SP, April/200
Illicit Money Flows as Motives for FDI
We examine the role of FDI in facilitating money laundering and illegal capital flight, focusing on transition economies’ FDI outflows because they largely reflect current investment decisions rather than the inertia of past decisions. We estimate a model of FDI outflows in which illicit money flows influence the volume of FDI directed toward countries considered to be centers of money laundering. We show that traditional models of FDI are not able to account for these investment flows and that our results are robust when additional explanatory variables such as host country tax rates, governance, corruption, and cultural differences between the home and host country are included in the model. We estimate that 6 to 10% of total FDI outflows and over 20% of FDI to money-laundering countries from our sample were made to facilitate illicit money flows
Gas inflows towards the nucleus of the active galaxy NGC7213
We present two-dimensional stellar and gaseous kinematics of the inner
0.8x1.1kpc^2 of the LINER/Seyfert 1 galaxy NGC7213, from optical spectra
obtained with the GMOS integral field spectrograph on the Gemini South
telescope at a spatial resolution of 60pc. The stellar kinematics shows an
average velocity dispersion of 177km/s, circular rotation with a projected
velocity amplitude of 50km/s and a kinematic major axis at a position angle of
-4degrees (west of north). From the average velocity dispersion we estimate a
black hole mass of M_BH=8_{-6}^{+16}x10^7 M_sun. The gas kinematics is
dominated by non-circular motions, mainly along two spiral arms extending from
the nucleus out to 4arcsec (280pc) to the NW and SE, that are cospatial with a
nuclear dusty spiral seen in a structure map of the nuclear region of the
galaxy. The projected gas velocities along the spiral arms show blueshifts in
the far side and redshifts in the near side, with values of up to 200km/s. This
kinematics can be interpreted as gas inflows towards the nucleus along the
spiral arms if the gas is in the plane of the galaxy. We estimate the mass
inflow rate using two different methods. The first is based of the observed
velocities and geometry of the flow, and gives a mass inflow rate in the
ionised gas of 7x10^-2 M_sun/yr. In the second method, we calculate the net
ionised gas mass flow rate through concentric circles of decreasing radii
around the nucleus resulting in mass inflow rates ranging from 0.4 M_sun/yr at
300pc down to 0.2 M_sun/yr at 100pc from the nucleus. These rates are larger
than necessary to power the active nucleus.Comment: 10 pages, 10 figures, accepted for publication in MNRA
Husimi-Wigner representation of chaotic eigenstates
Just as a coherent state may be considered as a quantum point, its
restriction to a factor space of the full Hilbert space can be interpreted as a
quantum plane. The overlap of such a factor coherent state with a full pure
state is akin to a quantum section. It defines a reduced pure state in the
cofactor Hilbert space. The collection of all the Wigner functions
corresponding to a full set of parallel quantum sections defines the
Husimi-Wigner reresentation. It occupies an intermediate ground between drastic
suppression of nonclassical features, characteristic of Husimi functions, and
the daunting complexity of higher dimensional Wigner functions. After analysing
these features for simpler states, we exploit this new representation as a
probe of numerically computed eigenstates of chaotic Hamiltonians. The
individual two-dimensional Wigner functions resemble those of semiclassically
quantized states, but the regular ring pattern is broken by dislocations.Comment: 21 pages, 7 figures (6 color figures), submitted to Proc. R. Soc.
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