16,217 research outputs found
Residual proton-neutron interactions and the scheme
We investigate the correlation between integrated proton-neutron interactions
obtained by using the up-to-date experimental data of binding energies and the
, the product of valence proton number and valence neutron
number with respect to the nearest doubly closed nucleus. We make corrections
on a previously suggested formula for the integrated proton-neutron
interaction. Our results demonstrate a nice, nearly linear, correlation between
the integrated p-n interaction and , which provides us
with a firm foundation of the applicability of the scheme
to nuclei far from the stability line.Comment: four pages, three figures, Physical Review C, in pres
The Forecasting Capacity of Housing Price Expectations
This study captures the essential elements of the price expectations of market participants in a rising market. Adopting a forward-looking approach, this paper explores the effectiveness of expectations as an indicator of forthcoming housing price changes in Hong Kong. Examination of the quarterly survey data from December 2003 to September 2007 indicates that both homeowners and non-homeowners tend to overestimate the probability of future housing price increases yet underestimate its volatility. This adds weight to the argument that market participants are generally not rational in the prediction of price movement. Homeowners, investors and potential home buyers have more or less the same level of confidence about the future market outlook. Like non-owners, they expect higher prices. The number of correct forecasts exceeds incorrect forecasts, suggesting that overall price expectations are fairly close to realization. It can be broadly concluded that the aggregate price expectations in the long run can be an appropriate forecasting tool for future market performance.Price expectations; Forecastability; Housing market; Hong Kong
Cosmological Reionization by Stellar Sources
I use cosmological simulations that incorporate a physically motivated
approximation to three-dimensional radiative transfer that recovers correct
asymptotic ionization front propagation speeds for some cosmologically relevant
density distributions transfer to investigate the process of the reionization
of the universe by ionizing radiation from proto-galaxies. Reionization
proceeds in three stages and occupies a large redshift range from z~15 until
z~5. During the first, ``pre-overlap'' stage, HII regions gradually expand into
the low density IGM, leaving behind neutral high density protrusions. During
the second, ``overlap'' stage, that occurs in about 10% of the Hubble time, HII
regions merge and the ionizing background rises by a large factor. During the
third, ``post-overlap'' stage, remaining high density regions are being
gradually ionized as the required ionizing photons are being produced.
Residual fluctuations in the ionizing background reach significant (more than
10%) levels for the Lyman-alpha forest absorption systems with column densities
above 10^14 - 10^15 cm^-2 at z=3 to 4.Comment: Revised version accepted for publication in ApJ. Color versions of
Fig. 3a-h in GIF format, full (unbinned) versions of Fig. 5, 6, and 13, as
well as MPEG animations are available at
http://casa.colorado.edu/~gnedin/GALLERY/rei_p.htm
Technique of quantum state transfer for a double Lambda atomic beam
The transfer technique of quantum states from light to collective atomic
excitations in a double type system is extended to matter waves in
this paper, as a novel scheme towards making a continuous atom laser. The
intensity of the output matter waves is found to be determined by the initial
relative phase of the two independent coherent probe lights, which may indicate
an interesting method for the measurement of initial relative phase of two
independent light sources.Comment: 5 pages, 2 figure
Why People Forward Emails to Others?
The issue of electronic mail (e-mail) communication has attracted much academic attention over the last two decades. Yet, little is known about why people forward emails to others. Through a review of the literature, this paper aims to investigate reasons why people forward emails and proposes several variables related to one\u27s intention of doing so. More specifically, we hypothesize that the higher degree the four possible variables are (the recipient’s trust in the email content, the recipient\u27s trust in the senders, intention to staying in touch with friends, and the receivers\u27 altruism trait), the more likely people will forward emails. On the other hand, we hypothesize that the lower degree the two possible variables are (the size of email file, and the cost of forwarding e-mail), the less likely people will forward emails
Scale-free networks with tunable degree distribution exponents
We propose and study a model of scale-free growing networks that gives a
degree distribution dominated by a power-law behavior with a model-dependent,
hence tunable, exponent. The model represents a hybrid of the growing networks
based on popularity-driven and fitness-driven preferential attachments. As the
network grows, a newly added node establishes new links to existing nodes
with a probability based on popularity of the existing nodes and a
probability based on fitness of the existing nodes. An explicit form of
the degree distribution is derived within a mean field approach. For
reasonably large , , where the
function is dominated by the behavior of for small
values of and becomes -independent as , and is a
model-dependent exponent. The degree distribution and the exponent
are found to be in good agreement with results obtained by extensive numerical
simulations.Comment: 12 pages, 2 figures, submitted to PR
Network Inoculation: Heteroclinics and phase transitions in an epidemic model
In epidemiological modelling, dynamics on networks, and in particular
adaptive and heterogeneous networks have recently received much interest. Here
we present a detailed analysis of a previously proposed model that combines
heterogeneity in the individuals with adaptive rewiring of the network
structure in response to a disease. We show that in this model qualitative
changes in the dynamics occur in two phase transitions. In a macroscopic
description one of these corresponds to a local bifurcation whereas the other
one corresponds to a non-local heteroclinic bifurcation. This model thus
provides a rare example of a system where a phase transition is caused by a
non-local bifurcation, while both micro- and macro-level dynamics are
accessible to mathematical analysis. The bifurcation points mark the onset of a
behaviour that we call network inoculation. In the respective parameter region
exposure of the system to a pathogen will lead to an outbreak that collapses,
but leaves the network in a configuration where the disease cannot reinvade,
despite every agent returning to the susceptible class. We argue that this
behaviour and the associated phase transitions can be expected to occur in a
wide class of models of sufficient complexity.Comment: 26 pages, 11 figure
Spectrum of Relativistic and Subrelativistic Cosmic Rays in the 100 pc Central Region
From the rate of hydrogen ionization and the gamma ray flux, we derived the
spectrum of relativistic and subrelativistic cosmic rays (CRs) nearby and
inside the molecular cloud Sgr B2 near the Galactic Center (GC). We studied two
cases of CR propagation in molecular clouds: free propagation and scattering of
particles by magnetic fluctuations excited by the neutral gas turbulence. We
showed that in the latter case CR propagation inside the cloud can be described
as diffusion with the coefficient cm s. For
the case of hydrogen ionization by subrelativistic protons, we showed that
their spectrum outside the cloud is quite hard with the spectral index
. The energy density of subrelativistic protons ( eV cm)
is one order of magnitude higher than that of relativistic CRs. These protons
generate the 6.4 keV emission from Sgr B2, which was about 30\% of the flux
observed by Suzaku in 2013. Future observations for the period after 2013 may
discover the background flux generated by subrelativistic CRs in Sgr B2.
Alternatively hydrogen ionization of the molecular gas in Sgr B2 may be caused
by high energy electrons. We showed that the spectrum of electron
bremsstrahlung is harder than the observed continuum from Sgr B2, and in
principle this X-ray component provided by electrons could be seen from the
INTEGRAL data as a stationary high energy excess above the observed spectrum
.Comment: 42 pages, 6 figures, accepted by Ap
- …