9,208 research outputs found
Price competition with consumer confusion
Copyright © 2013, INFORMS. Article posted with permission.This paper proposes a model in which identical sellers of a homogeneous product compete in both prices and price frames (i.e., ways to present price information). Frame choices affect the comparability of price offers and may cause consumer confusion and lower price sensitivity. In equilibrium, firms randomize their frame choices to obfuscate price comparisons and sustain positive profits. The nature of the equilibrium depends on whether frame differentiation or frame complexity is more confusing. Moreover, an increase in the number of competitors induces firms to rely more on frame complexity, and this may boost industry profits and lower consumer surplus
Exploratory studies of contact angle hysteresis, wetting of solidified rare gases and surface properties of mercury Final report
Contact angle hysteresis, wetting of solidified rare gases, and surface properties of mercur
The Mass Dependence of Star Formation Histories in Barred Spiral Galaxies
We performed a series of 29 gasdynamical simulations of disc galaxies, barred and unbarred, with various stellar masses, to study the impact of the bar on star formation history. Unbarred galaxies evolve very smoothly, with a star formation rate (SFR) that varies by at most a factor of three over a period of 2 Gyr. The evolution of barred galaxies is much more irregular, especially at high stellar masses. In these galaxies, the bar drives a substantial amount of gas toward the centre, resulting in a high SFR, and producing a starburst in the most massive galaxies. Most of the gas is converted into stars, and gas exhaustion leads to a rapid drop of star formation after the starburst. In massive barred galaxies (stellar mass M* > 2x10^10 Msun) the large amount of gas funnelled toward the centre is completely consumed by the starburst, while in lower-mass barred galaxies it is only partially consumed. Gas concentration is thus higher in lower-mass barred galaxies than it is in higher-mass ones. Even though unbarred galaxies funnelled less gas toward their centre, the lower SFR allows this gas to accumulate. At late times, the star formation efficiency is higher in barred galaxies than unbarred ones, enabling these galaxies to maintain a higher SFR with a smaller gas supply. Several properties, such as the global SFR, central SFR, or central gas concentration, vary monotonically with time for unbarred galaxies, but not for barred galaxies. Therefore one must be careful when comparing barred and unbarred galaxies that share one observational property, since these galaxies might be at very different stages of their respective evolution
The Mass Dependence of Star Formation Histories in Barred Spiral Galaxies
We performed a series of 29 gasdynamical simulations of disc galaxies, barred and unbarred, with various stellar masses, to study the impact of the bar on star formation history. Unbarred galaxies evolve very smoothly, with a star formation rate (SFR) that varies by at most a factor of three over a period of 2 Gyr. The evolution of barred galaxies is much more irregular, especially at high stellar masses. In these galaxies, the bar drives a substantial amount of gas toward the centre, resulting in a high SFR, and producing a starburst in the most massive galaxies. Most of the gas is converted into stars, and gas exhaustion leads to a rapid drop of star formation after the starburst. In massive barred galaxies (stellar mass M* > 2x10^10 Msun) the large amount of gas funnelled toward the centre is completely consumed by the starburst, while in lower-mass barred galaxies it is only partially consumed. Gas concentration is thus higher in lower-mass barred galaxies than it is in higher-mass ones. Even though unbarred galaxies funnelled less gas toward their centre, the lower SFR allows this gas to accumulate. At late times, the star formation efficiency is higher in barred galaxies than unbarred ones, enabling these galaxies to maintain a higher SFR with a smaller gas supply. Several properties, such as the global SFR, central SFR, or central gas concentration, vary monotonically with time for unbarred galaxies, but not for barred galaxies. Therefore one must be careful when comparing barred and unbarred galaxies that share one observational property, since these galaxies might be at very different stages of their respective evolution
Cosmic Ray Acceleration at the Forward Shock in Tycho's Supernova Remnant: Evidence from Chandra X-ray Observations
We present evidence for cosmic ray acceleration at the forward shock in
Tycho's supernova remnant (SNR) from three X-ray observables: (1) the proximity
of the contact discontinuity to the forward shock, or blast wave, (2) the
morphology of the emission from the rim of Tycho, and (3) the spectral nature
of the rim emission. We determine the locations of the blast wave (BW), contact
discontinuity (CD), and reverse shock (RS) around the rim of Tycho's supernova
remnant using a principal component analysis and other methods applied to new
Chandra data. The azimuthal-angle-averaged radius of the BW is 251". For the CD
and RS we find average radii of 241" and 183", respectively. Taking account of
projection effects, we find ratios of 1:0.93:0.70 (BW:CD:RS). We show these
values to be inconsistent with adiabatic hydrodynamical models of SNR
evolution. The CD:BW ratio can be explained if cosmic ray acceleration of ions
is occurring at the forward shock. The RS:BW ratio, as well as the strong Fe Ka
emission from the Tycho ejecta, imply that the RS is not accelerating cosmic
rays. We also extract radial profiles from ~34% of the rim of Tycho and compare
them to models of surface brightness profiles behind the BW for a purely
thermal plasma with an adiabatic shock. The observed morphology of the rim is
much more strongly peaked than predicted by the model, indicating that such
thermal emission is implausible here. Spectral analysis also implies that the
rim emission is non-thermal in nature, lending further support to the idea that
Tycho's forward shock is accelerating cosmic rays.Comment: 39 pages, 10 figures, accepted by Ap
HST Observations of SGR 0526-66: New Constraints on Accretion and Magnetar Models
Soft Gamma-ray Repeaters (SGRs) are among the most enigmatic sources known
today. Exhibiting huge X- and Gamma-ray bursts and flares, as well as soft
quiescent X-ray emission, their energy source remains a mystery. Just as
mysterious are the Anomalous X-ray pulsars (AXPs), which share many of the same
characteristics. Thanks to recent Chandra observations, SGR 0526-66, the first
SGR, now appears to be a transition object bridging the two classes, and
therefore observations of it have implications for both SGRs and AXPs. The two
most popular current models for their persistent emission are accretion of a
fossil disk or decay of an enormous (~10^15 G) magnetic field in a magnetar. We
show how deep optical observations of SGR 0526-66, the only SGR with small
enough optical extinction for meaningful observations, show no evidence of an
optical counterpart. These observation place strong new constraints on both
accretion disk and magnetar models, and suggest that the spectral energy
distribution may peak in the hard-UV. Almost all accretion disks are excluded
by the optical data, and a magnetar would require a ~10^15-10^16 G field.Comment: 23 pages, 5 figures. Accepted by Ap
Electroweak Physics, Experimental Aspects
Collider measurements on electroweak physics are summarised. Although the
precision on some observables is very high, no deviation from the Standard
Model of electroweak interactions is observed. The data allow to set stringent
limits on some models for new physics.Comment: Plenary Talk at the UK Phenomenology Workshop on Collider Physics,
Durham, 199
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