16 research outputs found
On the Origin of the Outgoing Black Hole Modes
The question of how to account for the outgoing black hole modes without
drawing upon a transplanckian reservoir at the horizon is addressed. It is
argued that the outgoing modes must arise via conversion from ingoing modes. It
is further argued that the back-reaction must be included to avoid the
conclusion that particle creation cannot occur in a strictly stationary
background. The process of ``mode conversion" is known in plasma physics by
this name and in condensed matter physics as ``Andreev reflection" or ``branch
conversion". It is illustrated here in a linear Lorentz non-invariant model
introduced by Unruh. The role of interactions and a physical short distance
cutoff is then examined in the sonic black hole formed with Helium-II.Comment: 12 pages, plain latex, 2 figures included using psfig; Analogy to
``Andreev reflection" in superfluid systems noted, references and
acknowledgment added, format changed to shorten tex
Structural and dynamical properties of superfluid helium: a density functional approach
We present a novel density functional for liquid 4He, properly accounting for
the static response function and the phonon-roton dispersion in the uniform
liquid. The functional is used to study both structural and dynamical
properties of superfluid helium in various geometries. The equilibrium
properties of the free surface, droplets and films at zero temperature are
calculated. Our predictions agree closely to the results of ab initio Monte
Carlo calculations, when available. The introduction of a phenomenological
velocity dependent interaction, which accounts for backflow effects, is
discussed. The spectrum of the elementary excitations of the free surface and
films is studied.Comment: 37 pages, REVTeX 3.0, figures on request at [email protected]
TEMPERATURE DEPENDENCE OF PHONONS IN LIQUID 4He
On a mesuré la diffusion de neutrons par 4He liquide aux vecteurs d'onde de 0.80 ; 1,13 ; 1,30 et 1,40 Å-1 et aux temperatures de 1,00 ; 1,38 ; 1,77 ; 1,97 ; 2,07 ; 2,12 ; 2,15 ; 2,26 et 4,21 K. On peut voir un pic "uniphonon" dans toutes les distributions lorsque T Tλ.The neutron scattering by liquid 4He for wave vectors of 0.80, 1.13, 1.30 and 1.40 Å-1 has been measured at 1.00, 1.38, 1.77, 1.97, 2.07, 2.12, 2.15, 2.26 and 4.21 K. A "one-phonon" peak is evident in all distributions for T Tλ