2,168 research outputs found
Strong Enhancement of Superconducting Correlation in a Two-Component Fermion Gas
We study high-density electron-hole (e-h) systems with the electron density
slightly larger than the hole density. We find a new superconducting phase, in
which the excess electrons form Cooper pairs moving in an e-h BCS phase. The
coexistence of the e-h and e-e orders is possible because e and h have opposite
charges, whereas analogous phases are impossible in the case of two fermion
species that have the same charge or are neutral. Most strikingly, the e-h
order enhances the superconducting e-h order parameter by more than one order
of magnitude as compared with that given by the BCS formula, for the same value
of the effective e-e attractive potential \lambda^{ee}. This new phase should
be observable in an e-h system created by photoexcitation in doped
semiconductors at low temperatures.Comment: 5 pages including 5 PostScript figure
The Discovery of Argon in Comet C/1995 O1 (Hale-Bopp)
On 30.14 March 1997 we observed the EUV spectrum of the bright comet C/1995
O1 (Hale-Bopp) at the time of its perihelion, using our EUVS sounding rocket
telescope/spectrometer. The spectra reveal the presence H Ly beta, O+, and,
most notably, Argon. Modelling of the retrieved Ar production rates indicates
that comet Hale-Bopp is enriched in Ar relative to cosmogonic expectations.
This in turn indicates that Hale-Bopp's deep interior has never been exposed to
the 35-40 K temperatures necessary to deplete the comet's primordial argon
supply.Comment: 9 pages, 2 figures. ApJ, 545, in press (2000
Outbursts from IGR J17473-2721
We have investigated the outbursts of IGR J17473-2721. We analyzed all
available observations carried out by RXTE on IGR J17473-2721 during its later
outburst and as well all the available SWIFT/BAT data. The flux of the latter
outburst rose in ~ one month and then kept roughly constant for the following ~
two months. During this time period, the source was in a low/hard state. The
source moved to a high/soft state within the following three days, accompanied
by the occurrence of an additional outburst at soft X-rays and the end of the
preceding outburst in hard X-rays. During the decay of this soft outburst, the
source went back to a low/hard state within 6 days, with a luminosity 4 times
lower than the first transition. This shows a full cycle of the hysteresis in
transition between the hard and the soft states. The fact that the flux
remained roughly constant for ~ two months at times prior to the spectral
transition to a high/soft state might be regarded as the result of balancing
the evaporation of the inner disk and the inward accretion flow, in a model in
which the state transition is determined by the mass flow rate. Such a balance
might be broken via an additional mass flow accreting onto the inner disk,
which lightens the extra soft outburst and causes the state transition.
However, the possibility of an origin of the emission from the jet during this
time period cannot be excluded. The spectral analysis suggests an inclined XRB
system for IGR J17473-2721. Such a long-lived preceding low/hard state makes
IGR J17473-2721 resemble the behavior of outbursts seen in black hole X-ray
binaries like GX 339-4.Comment: A&A in pres
Time of life as it is in LiFeAs
The time of life of fermionic quasiparticles, the distribution of which in
the momentum-energy space can be measured by angle resolved photoemission
(ARPES), is the first quantity to look for fingerprints of interaction
responsible for the superconducting pairing. Such an approach has been recently
used for superconducting cuprates, but its direct application to pnictides was
not possible due to essential three-dimensionality of the electronic band
structure and magnetic ordering. Here, we report the investigation of the
quasiparticle lifetime in LiFeAs, a non-magnetic stoichiometric superconductor
with a well separated two-dimensional band. We have found two energy scales:
the lower one contains clear fingerprints of optical phonon modes while the
higher scale indicates a presence of strong electron-electron interaction. The
result suggests that LiFeAs is a phonon mediated superconductor with strongly
enhanced electronic density of states at the Fermi level.Comment: reevaluated electron-phonon coupling strength, added reference
Money buys happiness when spending fits our personality
In contrast to decades of research reporting surprisingly weak relationships between consumption and happiness, recent findings suggest that money can indeed increase happiness if it is spent the “right way” (e.g., on experiences or on other people). Drawing on the concept of psychological fit, we extend this research by arguing that individual differences play a central role in determining the “right” type of spending to increase well-being. In a field study using more than 76,000 bank-transaction records, we found that individuals spend more on products that match their personality, and that people whose purchases better match their personality report higher levels of life satisfaction. This effect of psychological fit on happiness was stronger than the effect of individuals’ total income or the effect of their total spending. A follow-up study showed a causal effect: Personality-matched spending increased positive affect. In summary, when spending matches the buyer’s personality, it appears that money can indeed buy happiness.S.M. was supported by the National German Academic Foundation; J.G. was supported by the Economic and Social Research Council
Ultraviolet observations of the Saturnian north aurora and polar haze distribution with the HST-FOC
Near simultaneous observations of the Saturnian H2 north ultraviolet aurora and the polar haze were made at 153 nm and 210 nm respectively with the Faint Object Camera on board the Hubble Space Telescope. The auroral observations cover a complete rotation of the planet and, when co-added, reveal the presence of an auroral emission near 80 deg N with a peak brightness of about 150 kR of total H2 emission. The maximum optical depth of the polar haze layer is found to be located approximately 5 deg equatorward of the auroral emission zone. The haze particles are presumably formed by hydrocarbon aerosols initiated by H2+ auroral production. In this case, the observed haze optical depth requires an efficiency of aerosol formation of about 6 percent, indicating that auroral production of hydrocarbon aerosols is a viable source of high-latitude haze
Rocket FUV Observations of the Io Plasma Torus During the Shoemaker-Levy/9 Impacts
We observed the Io torus from 820-1140 A on universal time (UT) 20.25 July 1994 from a sounding rocket telescope/spectrograph. These observations serve as only the fourth published spectrum of the torus in this wavelength range, and the only far ultraviolet (FUV) data documenting the state of the torus during the Shoemaker Levy 9 Impacts
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