30,511 research outputs found
Generalized contact process with two symmetric absorbing states in two dimensions
We explore the two-dimensional generalized contact process with two absorbing
states by means of large-scale Monte-Carlo simulations. In part of the phase
diagram, an infinitesimal creation rate of active sites between inactive
domains is sufficient to take the system from the inactive phase to the active
phase. The system therefore displays two different nonequilibrium phase
transitions. The critical behavior of the generic transition is compatible with
the generalized voter (GV) universality class, implying that the
symmetry-breaking and absorbing transitions coincide. In contrast, the
transition at zero domain-boundary activation rate is not critical.Comment: 7 pages, 7 eps figures included, final version as publishe
Defect energy of infinite-component vector spin glasses
We compute numerically the zero temperature defect energy, Delta E, of the
vector spin glass in the limit of an infinite number of spin components m, for
a range of dimensions 2 <= d <= 5. Fitting to Delta E ~ L^theta, where L is the
system size, we obtain: theta = -1.54 (d=2), theta = -1.04 (d=3), theta = -0.67
(d=4) and theta = -0.37 (d=5). These results show that the lower critical
dimension, d_l (the dimension where theta changes sign), is significantly
higher for m=infinity than for finite m (where 2 < d_l < 3).Comment: 4 pages, 5 figure
Dipole-Allowed Direct Band Gap Silicon Superlattices
Silicon is the most popular material used in electronic devices. However, its
poor optical properties owing to its indirect band gap nature limit its usage
in optoelectronic devices. Here we present the discovery of super-stable
pure-silicon superlattice structures that can serve as promising materials for
solar cell applications and can lead to the realization of pure Si-based
optoelectronic devices. The structures are almost identical to that of bulk Si
except that defective layers are intercalated in the diamond lattice. The
superlattices exhibit dipole-allowed direct band gaps as well as indirect band
gaps, providing ideal conditions for the investigation of a direct-to-indirect
band gap transition. The transition can be understood in terms of a novel
conduction band originating from defective layers, an overlap between the
valence- and conduction-band edge states at the interface layers, and zone
folding with quantum confinement effects on the conduction band of
non-defective bulk-like Si. The fact that almost all structural portions of the
superlattices originate from bulk Si warrants their stability and good lattice
matching with bulk Si. Through first-principles molecular dynamics simulations,
we confirmed their thermal stability and propose a possible method to
synthesize the defective layer through wafer bonding
Earnings and Dividend Announcements is there a Corroboration Effect?
We examine abnormal stock returns surrounding contemporaneous earnings and dividend announcements in order to determine whether investors evaluate the two announcements in relation to each other.We find that there is a statistically significant interaction effect.The abnormal return corresponding to any earnings or dividend announcement depends upon the value of the other announcement. This evidence suggests the existence of a corroborative relationship between the two announcements. Investors give more credence to unanticipated dividend increases or decreases when earnings are also above or below expectations, and vice versa.
Does higher education foster critical and creative learners? An exploration of two universities in South Korea and the USA
This paper describes two studies that explore students' beliefs about critical and creative learning at two universities, and considers the implications of those beliefs in comparison to the universities' stated education goals. One is a mixed method study of students at a top university in Korea, and the second is a comparative study between the Korean university and a United States (US) university. The first study found that both high-achievers and the general population at a top Korean university perceived their critical and creative abilities as lower than their receptive learning abilities, and that higher achievers were neither more critical nor creative than lower achievers. The second study finds that the Korean university students, compared to US students, were more likely to rate their receptive learning ability as higher than their critical and creative learning abilities. Comparisons across year of higher education (HE) suggest that Korean students' perceptions did not significantly change with respect to year in school, while US students' perceptions of critical learning abilities significantly increased across school years. Results are discussed with respect to the impact of culture, epistemological beliefs, and HE instruction on critical and creative learning
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