7,570 research outputs found
Detection techniques for tenuous planetary atmospheres Fifth six-month report, 1 Jul. - 30 Dec. 1965
Physical methods description for detection and analysis of tenuous planetary atmospheric component gases, especially water vapo
Scale invariant thermodynamics of a toroidally trapped Bose gas
We consider a system of bosonic atoms in an axially symmetric harmonic trap
augmented with a two dimensional repulsive Gaussian optical potential. We find
an expression for the grand free energy of the system for configurations
ranging from the harmonic trap to the toroidal regime. For large tori we
identify an accessible regime where the ideal gas thermodynamics of the system
are found to be independent of toroidal radius. This property is a consequence
of an invariant extensive volume of the system that we identify analytically in
the regime where the toroidal potential is radially harmonic. In considering
corrections to the scale invariant transition temperature, we find that the
first order interaction shift is the dominant effect in the thermodynamic
limit, and is also scale invariant. We also consider adiabatic loading from the
harmonic to toroidal trap configuration, which we show to have only a small
effect on the condensate fraction of the ideal gas, indicating that loading
into the scale invariant regime may be experimentally practical.Comment: 10 pages, 3 figures, to appear in Phys. Rev. A, typos corrected,
references added, rewritten to emphasize generalized volume. Results
unchange
dimensional Dirac equation with non Hermitian interaction
We study dimensional Dirac equation with non Hermitian interactions,
but real energies. In particular, we analyze the pseudoscalar and scalar
interactions in detail, illustrating our observations with some examples. We
also show that the relevant hidden symmetry of the Dirac equation with such an
interaction is pseudo supersymmetry.Comment: 9 page
Families of quasi-exactly solvable extensions of the quantum oscillator in curved spaces
We introduce two new families of quasi-exactly solvable (QES) extensions of
the oscillator in a -dimensional constant-curvature space. For the first
three members of each family, we obtain closed-form expressions of the energies
and wavefunctions for some allowed values of the potential parameters using the
Bethe ansatz method. We prove that the first member of each family has a hidden
sl(2,) symmetry and is connected with a QES equation of the first
or second type, respectively. One-dimensional results are also derived from the
-dimensional ones with , thereby getting QES extensions of the
Mathews-Lakshmanan nonlinear oscillator.Comment: 30 pages, 8 figures, published versio
Logarithmic correction to scaling for multi-spin strings in the AdS_5 black hole background
We find new explicit solutions describing closed strings spinning with equal
angular momentum in two independent planes in the black hole spacetime.
These are folded strings in the radial direction and also winding
times around an angular direction. We especially consider these solutions in
the long string and high temperature limit, where it is shown that there is a
logarithmic correction to the scaling between energy and spin. This is similar
to the one-spin case. The strings are spinning, or actually orbiting around the
black hole of the black hole spacetime, similarly to solutions
previously found in black hole spacetimes.Comment: 11 pages, Final version, To appear in IJMP
Cooling in the single-photon strong-coupling regime of cavity optomechanics
In this paper we discuss how red-sideband cooling is modified in the
single-photon strong-coupling regime of cavity optomechanics where the
radiation pressure of a single photon displaces the mechanical oscillator by
more than its zero-point uncertainty. Using Fermi's Golden rule we calculate
the transition rates induced by the optical drive without linearizing the
optomechanical interaction. In the resolved-sideband limit we find
multiple-phonon cooling resonances for strong single-photon coupling that lead
to non-thermal steady states including the possibility of phonon anti-bunching.
Our study generalizes the standard linear cooling theory.Comment: 4 pages, 3 figure
The subdiffusive target problem: Survival probability
The asymptotic survival probability of a spherical target in the presence of
a single subdiffusive trap or surrounded by a sea of subdiffusive traps in a
continuous Euclidean medium is calculated. In one and two dimensions the
survival probability of the target in the presence of a single trap decays to
zero as a power law and as a power law with logarithmic correction,
respectively. The target is thus reached with certainty, but it takes the trap
an infinite time on average to do so. In three dimensions a single trap may
never reach the target and so the survival probability is finite and, in fact,
does not depend on whether the traps move diffusively or subdiffusively. When
the target is surrounded by a sea of traps, on the other hand, its survival
probability decays as a stretched exponential in all dimensions (with a
logarithmic correction in the exponent for ). A trap will therefore reach
the target with certainty, and will do so in a finite time. These results may
be directly related to enzyme binding kinetics on DNA in the crowded cellular
environment.Comment: 6 pages. References added, improved account of previous results and
typos correcte
Unified Treatment of Mixed Vector-Scalar Screened Coulomb Potentials for Fermions
The problem of a fermion subject to a general mixing of vector and scalar
screened Coulomb potentials in a two-dimensional world is analyzed and
quantization conditions are found.Comment: 7 page
Spectral signatures of magnetic Bloch oscillations in one-dimensional easy-axis ferromagnets
Domain walls in a one-dimensional gapped easy-axis ferromagnet can exhibit
Bloch oscillations in an applied magnetic field. We investigate how exchange
couplings modify this behavior within an approximation based on noninteracting
domain-wall bound states. In particular, we obtain analytical results for the
spectrum and the dynamic structure factor, and show where in momentum space to
expect equidistant energy levels, the Wannier-Zeeman ladder, which is the
spectral signature of magnetic Bloch oscillations. We compare our results to
previous calculations employing a single domain-wall approximation, and make
predictions relevant for the material .Comment: 12 pages, 14 figure
PT-Invariant Periodic Potentials with a Finite Number of Band Gaps
We obtain the band edge eigenstates and the mid-band states for the complex,
PT-invariant generalized associated Lam\'e potentials V^{PT}(x)=-a(a+1)m
\sn^2(y,m)-b(b+1)m {\sn^2 (y+K(m),m)} -f(f+1)m {\sn^2
(y+K(m)+iK'(m),m)}-g(g+1)m {\sn^2 (y+iK'(m),m)}, where ,
and there are four parameters . This work is a substantial
generalization of previous work with the associated Lam\'e potentials
V(x)=a(a+1)m\sn^2(x,m)+b(b+1)m{\sn^2 (x+K(m),m)} and their corresponding
PT-invariant counterparts , both of which involving
just two parameters . We show that for many integer values of ,
the PT-invariant potentials are periodic problems with a finite
number of band gaps. Further, usingsupersymmetry, we construct several
additional, new, complex, PT-invariant, periodic potentials with a finite
number of band gaps. We also point out the intimate connection between the
above generalized associated Lam\'e potential problem and Heun's differential
equation.Comment: 30 pages, 0 figure
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