13,551 research outputs found
Fano-Kondo effect in a two-level system with triple quantum dots: shot noise characteristics
We theoretically compare transport properties of Fano-Kondo effect with those
of Fano effect. We focus on shot noise characteristics of a triple quantum dot
(QD) system in the Fano-Kondo region at zero temperature, and discuss the
effect of strong electric correlation in QDs. We found that the modulation of
the Fano dip is strongly affected by the on-site Coulomb interaction in QDs.Comment: 4 pages, 6figure
Spin-Peierls states of quantum antiferromagnets on the lattice
We discuss the quantum paramagnetic phases of Heisenberg antiferromagnets on
the 1/5-depleted square lattice found in . The possible phases of
the quantum dimer model on this lattice are obtained by a mapping to a
quantum-mechanical height model. In addition to the ``decoupled'' phases found
earlier, we find a possible intermediate spin-Peierls phase with
spontaneously-broken lattice symmetry. Experimental signatures of the different
quantum paramagnetic phases are discussed.Comment: 9 pages; 2 eps figure
Non-Abelian quantized Hall states of electrons at filling factors 12/5 and 13/5 in the first excited Landau level
We present results of extensive numerical calculations on the ground state of
electrons in the first excited (n=1) Landau level with Coulomb interactions,
and including non-zero thickness effects, for filling factors 12/5 and 13/5 in
the torus geometry. In a region that includes these experimentally-relevant
values, we find that the energy spectrum and the overlaps with the trial states
support the previous hypothesis that the system is in the non-Abelian k = 3
liquid phase we introduced in a previous paper.Comment: 5 pages (Revtex4), 7 figure
The missing metals problem. III How many metals are expelled from galaxies?
[Abridged] We revisit the metal budget at z~2. In the first two papers of
this series, we already showed that ~30% (to <60% if extrapolating the LF) of
the metals are observed in all z~2.5 galaxies detected in current surveys.
Here, we extend our analysis to the metals outside galaxies, i.e. in
intergalactic medium (IGM), using observational data and analytical
calculations. Our results for the two are strikingly similar: (1)
Observationally, we find that, besides the small (5%) contribution of DLAs, the
forest and sub-DLAs contribute subtantially to make <30--45% of the metal
budget, but neither of these appear to be sufficient to close the metal budget.
The forest accounts for 15--30% depending on the UV background, and sub-DLAs
for >2% to <17% depending on the ionization fraction. Together, the `missing
metals' problem is substantially eased. (2) We perform analytical calculations
based on the effective yield--mass relation. At z=2, we find that the method
predicts that 2$--50% of the metals have been ejected from galaxies into the
IGM, consistent with the observations. The metal ejection is predominantly by
L<1/3L_B^*(z=2) galaxies, which are responsible for 90% the metal enrichment,
while the 50 percentile is at L~1/10L^*_B(z=2). As a consequence, if indeed 50%
of the metals have been ejected from galaxies, 3--5 bursts of star formation
are required per galaxy prior to z=2. The ratio between the mass of metals
outside galaxies to those in stars has changed from z=2 to z=0: it was 2:1 or
1:1 and is now 1:8 or 1:9. This evolution implies that a significant fraction
of the IGM metals will cool and fall back into galaxies.Comment: 18pages, MNRAS, in press; small changes to match proofs; extended
version with summary tabl
Mars Spacecraft Power System Development Final Report
Development of optimum Mariner spacecraft power system for application to future flyby and orbiter mission
Condensation of `composite bosons' in a rotating BEC
We provide evidence for several novel phases in the dilute limit of rotating
BECs. By exact calculation of wavefunctions and energies for small numbers of
particles, we show that the states near integer angular momentum per particle
are best considered condensates of composite entities, involving vortices and
atoms. We are led to this result by explicit comparison with a description
purely in terms of vortices. Several parallels with the fractional quantum Hall
effect emerge, including the presence of the Pfaffian state.Comment: 4 pages, Latex, 3 figure
Ground State Entropy of the Potts Antiferromagnet on Cyclic Strip Graphs
We present exact calculations of the zero-temperature partition function
(chromatic polynomial) and the (exponent of the) ground-state entropy for
the -state Potts antiferromagnet on families of cyclic and twisted cyclic
(M\"obius) strip graphs composed of -sided polygons. Our results suggest a
general rule concerning the maximal region in the complex plane to which
one can analytically continue from the physical interval where . The
chromatic zeros and their accumulation set exhibit the rather
unusual property of including support for and provide further
evidence for a relevant conjecture.Comment: 7 pages, Latex, 4 figs., J. Phys. A Lett., in pres
Photoionization of Galactic Halo Gas by Old Supernova Remnants
We present new calculations on the contribution from cooling hot gas to the
photoionization of warm ionized gas in the Galaxy. We show that hot gas in
cooling supernova remnants (SNRs) is an important source of photoionization,
particularly for gas in the halo. We find that in many regions at high latitude
this source is adequate to account for the observed ionization so there is no
need to find ways to transport stellar photons from the disk. The flux from
cooling SNRs sets a floor on the ionization along any line of sight. Our model
flux is also shown to be consistent with the diffuse soft X-ray background and
with soft X-ray observations of external galaxies.
We consider the ionization of the clouds observed towards the halo star HD
93521, for which there are no O stars close to the line of sight. We show that
the observed ionization can be explained successfully by our model EUV/soft
X-ray flux from cooling hot gas. In particular, we can match the H alpha
intensity, the S++/S+ ratio, and the C+* column. From observations of the
ratios of columns of C+* and either S+ or H0, we are able to estimate the
thermal pressure in the clouds. The slow clouds require high (~10^4 cm^-3 K)
thermal pressures to match the N(C+*)/N(S+) ratio. Additional heating sources
are required for the slow clouds to maintain their ~7000 K temperatures at
these pressures, as found by Reynolds, Hausen & Tufte (1999).Comment: AASTeX 5.01; 34 pages, 2 figures; submitted to Astrophysical Journa
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