6,429 research outputs found
Sealed bid second price auctions with discrete bids
A single item is sold to two bidders by way of a sealed bid second price auction in which bids are restricted to a set of discrete values. Restricting attention to symmetric pure strategy behavior on the part of bidders, a unique equilibrium exists. When following these equilibrium strategies bidders may bid strictly above or below their valuation, implying that the item may be awarded to a bidder other than the high valuation bidder. In an auction with two acceptable bids, the expected revenue of the seller may be maximized by a high bid level not equal to the highest possible bidder valuation and may exceed the expected revenue from an analogous second price auction with continuous bidding (and no reserve price). With three acceptable bids, a revenue maximizing seller may choose unevenly spaced bids. With an arbitrary number of evenly spaced bids, as the number of acceptable bids is increased, the expected revenue of the seller and the probability of ex post inefficiency both may either increase or decrease
Cognitive Bias Modification: Past Perspectives, Current Findings, and Future Applications
Research conducted within the general paradigm of Cognitive Bias Modification (CBM) reveals that emotional biases in attention, interpretation, and memory are not merely associated with emotional disorders but contribute to them. After briefly describing research on both emotional biases and their modification, we examine similarities between CBM paradigms and older experimental paradigms used in research on learning and memory. We also compare the techniques and goals of CBM research to other approaches to understanding cognition/emotion interactions. From a functional perspective, the CBM tradition reminds us to use experimental tools to evaluate assumptions about clinical phenomena and more generally, about causal relationships between cognitive processing and emotion
Unparticle effects in rare (t -> c g g) decay
Rare (t -> c g g) decay can only appear at loop level in the Standard Model
(SM), and naturally they are strongly suppressed. These flavor changing decays
induced by the mediation of spin-0 and spin-2 unparticles, can appear at tree
level in unparticle physics. In this work the virtual effects of unparticle
physics in the flavor-changing (t -> c g g) decay is studied. Using the SM
result for the branching ratio of the (t -> c g g) decay, the parameter space
of d_U and Lambda_U, where the branching ratio of this decay exceeds the one
predicted by the SM, is obtained. Measurement of the branching ratio larger
than 10^(-9) can give valuable information for establishing unparticle physics.Comment: 15 pages, 7 figures, LaTeX formatte
Modeling of nutation-precession: very long baseline interferometry results
Analysis of over 20 years of very long baseline
interferometry data (VLBI) yields estimates of the
coefficients of the nutation series with standard deviations
ranging from 5 microseconds of arc (μas) for the terms
with periods <400 days to 38 µas for the
longest-period terms. The largest deviations between the VLBI
estimates of the amplitudes of terms in the nutation series
and the theoretical values from the Mathews-Herring-Buffett
(MHB2000) nutation series are 56 ± 38 μas
(associated with two of the 18.6 year nutations). The
amplitudes of nutational terms with periods <400 days
deviate from the MHB2000 nutation series values at the level
standard deviation. The estimated correction to the IAU-1976
precession constant is -2.997 ± 0.008 mas
yr-1 when the coefficients of the MHB2000 nutation
series are held fixed and is consistent with that inferred
from the MHB2000 nutation theory. The secular change in the
obliquity of the ecliptic is estimated to be -0.252 ±
0.003 mas yr-1. When the coefficients of the
largest-amplitude terms in the nutation series are estimated,
the precession constant correction and obliquity rate are
estimated to be -2.960 ± 0.030 and -0.237 ± 0.012
mas yr-1. Significant variations in the freely
excited retrograde free core nutation mode are observed over
the 20 years. During this time the amplitude has decreased
from -300 ± 50 μas in the mid-1980s to nearly zero
by the year 2000. There is evidence that the amplitude of the
mode in now increasing again
Bulk Viscosity, Decaying Dark Matter, and the Cosmic Acceleration
We discuss a cosmology in which cold dark-matter particles decay into
relativistic particles. We argue that such decays could lead naturally to a
bulk viscosity in the cosmic fluid. For decay lifetimes comparable to the
present hubble age, this bulk viscosity enters the cosmic energy equation as an
effective negative pressure. We investigate whether this negative pressure is
of sufficient magnitude to account fo the observed cosmic acceleration. We show
that a single decaying species in a flat, dark-matter dominated cosmology
without a cosmological constant cannot reproduce the observed
magnitude-redshift relation from Type Ia supernovae. However, a delayed bulk
viscosity, possibly due to a cascade of decaying particles may be able to
account for a significant fraction of the apparent cosmic acceleration.
Possible candidate nonrelativistic particles for this scenario include sterile
neutrinos or gauge-mediated decaying supersymmetric particles.Comment: 7 pages, 4 figure
Structural features of adenovirus 2 virus-associated RNA required for binding to the protein kinase DAI
The double-stranded RNA activated protein kinase DAI contains an RNA binding domain consisting of two copies of a double-stranded RNA binding motif. We have investigated the role of RNA structure in the interaction between DAI and the structured single-stranded RNA, adenovirus VA RNAI, which inhibits DAI activation. Mutations in the apical stem, terminal stem, and central domain of the RNA were tested to assess the contribution of these elements to DAI binding in vitro. The data demonstrate that over half a turn of intact apical stem is required for the interaction and that there is a correlation between the binding of apical stem mutants and their ability to function both in vivo and in vitro. There was also evidence of preference for GC-rich sequence in the proximal region of the apical stem. In the central domain the correlation between binding and function of mutant RNAs was poor, suggesting that at least some of this region plays no direct role in binding to DAI, despite its functional importance. Exceptionally, central domain mutations that encroached on the phylogenetically conserved stem 4 of VA RNA disrupted binding, and complementary mutations in this sequence partially restored binding. Measurement of the binding of wild-type VA RNAI to DAI and p20, a truncated form of the protein containing the RNA binding domains alone, under various ionic conditions imply that the major interactions are electrostatic and occur via the protein's RNA binding domain. However, differences between full-length DAI and p20 in their binding to mutants in the conserved stem suggest that regions outside the RNA binding domain also participate in the binding. The additional interactions are likely to be non-ionic, and may be important for preventing DAI activation during virus infection
On-demand or Spot? Selling the cloud to risk-averse customers
In Amazon EC2, cloud resources are sold through a combination of an on-demand
market, in which customers buy resources at a fixed price, and a spot market,
in which customers bid for an uncertain supply of excess resources. Standard
market environments suggest that an optimal design uses just one type of
market. We show the prevalence of a dual market system can be explained by
heterogeneous risk attitudes of customers. In our stylized model, we consider
unit demand risk-averse bidders. We show the model admits a unique equilibrium,
with higher revenue and higher welfare than using only spot markets.
Furthermore, as risk aversion increases, the usage of the on-demand market
increases. We conclude that risk attitudes are an important factor in cloud
resource allocation and should be incorporated into models of cloud markets.Comment: Appeared at WINE 201
Direct Signals for Large Extra Dimensions in the Production of Fermion Pairs at Linear Colliders
We analyze the potentiality of the new generation of linear
colliders to search for large extra dimensions via the production of fermion
pairs in association with Kaluza-Klein gravitons (G), i.e. . This process leads to a final state exhibiting a significant amount
of missing energy in addition to acoplanar lepton or jet pairs. We study in
detail this reaction using full tree level contibutions due to the graviton
emission and the standard model backgrounds. After choosing the cuts to enhance
the signal, we show that a linear collider with a center-of-mass energy of 500
GeV will be able to probe quantum gravity scales from 0.96(0.86) up to 4.1(3.3)
TeV at 2(5) level, depending on the number of extra dimensions.Comment: 19 pages, 5 figures. Using RevTex, axodraw.sty. Discussion was
extended. No changes in the results. Accepted for publication by Phys. Rev.
Possible explanation for star-crushing effect in binary neutron star simulations
A possible explanation is suggested for the controversial star-crushing
effect seen in numerical simulations of inspiraling neutron star binaries by
Wilson, Mathews and Marronetti (WMM). An apparently incorrect definition of
momentum density in the momentum constraint equation used by WMM gives rise to
a post-1-Newtonian error in the approximation scheme. We show by means of an
analytic, post-1-Newtonian calculation that this error causes an increase of
the stars' central densities which is of the order of several percent when the
stars are separated by a few stellar radii, in agreement with what is seen in
the simulations.Comment: 4 pages, 1 figure, uses revetx macros, minor revision
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