13,247 research outputs found
Detectability of High Redshift Ellipticals in the Hubble Deep Field
Relatively few intensively star-forming galaxies at redshifts z>2.5 have been
found in the Hubble Deep Field (HDF). This has been interpreted to imply a low
space density of elliptical galaxies at high z, possibly due to a late (z<2.5)
epoch of formation, or to dust obscuration of the ellipticals that are forming
at z~3. I use HST UV (2300 Ang) images of 25 local early-type galaxies to
investigate a third option, that ellipticals formed at z>4.5, and were fading
passively by 2<z<4.5. Present-day early-types are faint and centrally
concentrated in the UV. If ellipticals formed their stars in a short burst at
z>4.5, and have faded passively to their present brightnesses at UV
wavelengths, they would generally be below the HDF detection limits in any of
its bands at z>2.5. Quiescent z ~ 3 ellipticals, if they exist, should turn up
in sufficiently deep IR images.Comment: AAS LaTex, 11 pages, 1 table, 1 figure, some corrections and
clarifications, accepted for publication in ApJ
Velocity dominated singularities in the cheese slice universe
We investigate the properties of spacetimes resulting from matching together
exact solutions using the Darmois matching conditions. In particular we focus
on the asymptotically velocity term dominated property (AVTD). We propose a
criterion that can be used to test if a spacetime constructed from a matching
can be considered AVTD. Using the Cheese Slice universe as an example, we show
that a spacetime constructed from a such a matching can inherit the AVTD
property from the original spacetimes. Furthermore the singularity resulting
from this particular matching is an AVTD singularity.Comment: 11 pages, 3 figures, accepted for publication in the International
Journal of Modern Physics
Are We Understating the Impact of Economic Conditions on Welfare Rolls?
In this brief we argue that welfare participation is more sensitive to economic conditions than previously believed. Why? Prior research focused on short-term economic fluctuations and ignored differences between high- and low-skilled workers. As welfare is long-term (i.e., permanent) it makes more sense to make comparisons with long-term economic trends. Also, since low-skilled workers are more likely to end up on welfare, it is proper to focus on their economic opportunities. Thus, we focus on the long-term impact of economic conditions on welfare participation, and we concentrate our analysis on low-skilled workers. Specifically, we analyze long-term changes in the supply of high-paying jobs for coal and steel workers as they affect certain heavy coal- and steel-producing regions of the United States during the 1970s and 1980s. Our findings indicate that welfare participation in these regions closely mirrors the long-term local availability of high-paying jobs for low-skilled workers. This has serious policy implications for the long-term success of welfare reform.
The Relation of Thermal Fluctuation and Information-Entropy for One-Dimensional Rindler Oscillator
Within the framework of thermo-field-dynamics (TFD), the
information-entropies associated with the measurements of position and momentum
for one-dimensional Rindler oscillator are derived, and the connection between
its information-entropy and thermal fluctuation is obtained. A conclusion is
drawn that the thermal fluctuation leads to the loss of information.Comment: 14 pages, 1 figur
Are Children "Normal"?
We examine Becker's (1960) contention that children are "normal." For the cross section of non-Hispanic white married couples in the U.S., we show that when we restrict comparisons to similarly-educated women living in similarly-expensive locations, completed fertility is positively correlated with the husband's income. The empirical evidence is consistent with children being "normal." In an effort to show causal effects, we analyze the localized impact on fertility of the mid-1970s increase in world energy prices â an exogenous shock that substantially increased men's incomes in the Appalachian coal-mining region. Empirical evidence for that population indicates that fertility increases in men's income.economics of fertility, location choice, Appalachian fertility
Distinguishing Supersymmetry From Universal Extra Dimensions or Little Higgs Models With Dark Matter Experiments
There are compelling reasons to think that new physics will appear at or
below the TeV-scale. It is not known what form this new physics will take,
however. Although The Large Hadron collider is very likely to discover new
particles associated with the TeV-scale, it may be difficult for it to
determine the nature of those particles, whether superpartners, Kaluza-Klein
modes or other states. In this article, we consider how direct and indirect
dark matter detection experiments may provide information complementary to
hadron colliders, which can be used to discriminate between supersymmetry,
models with universal extra dimensions, and Little Higgs theories. We find
that, in many scenarios, dark matter experiments can be effectively used to
distinguish between these possibilities.Comment: 23 pages, 7 figures, references added in version
Magnetic Field Uniformity Across the GF 9-2 YSO, L1082C Dense Core, and GF 9 Filamentary Dark Cloud
The orientation of the magnetic field (B-field) in the filamentary dark cloud
GF 9 was traced from the periphery of the cloud into the L1082C dense core that
contains the low-mass, low-luminosity Class 0 young stellar object (YSO) GF 9-2
(IRAS 20503+6006). This was done using SOFIA HAWC+ dust thermal emission
polarimetry (TEP) at 216 um in combination with Mimir near-infrared background
starlight polarimetry (BSP) conducted at H-band (1.6 um) and K-band (2.2 um).
These observations were augmented with published I-band (0.77 um) BSP and
Planck 850 um TEP to probe B-field orientations with offset from the YSO in a
range spanning 6000 AU to 3 pc. No strong B-field orientation change with
offset was found, indicating remarkable uniformity of the B-field from the
cloud edge to the YSO environs. This finding disagrees with weak-field models
of cloud core and YSO formation. The continuity of inferred B-field
orientations for both TEP and BSP probes is strong evidence that both are
sampling a common B-field that uniformly threads the cloud, core, and YSO
region. Bayesian analysis of Gaia DR2 stars matched to the Mimir BSP stars
finds a distance to GF 9 of 270 +/- 10 pc. No strong wavelength dependence of
B-field orientation angle was found, contrary to previous claims.Comment: 18 pages, 6 figures ApJ, accepte
Entanglement requirements for implementing bipartite unitary operations
We prove, using a new method based on map-state duality, lower bounds on
entanglement resources needed to deterministically implement a bipartite
unitary using separable (SEP) operations, which include LOCC (local operations
and classical communication) as a particular case. It is known that the Schmidt
rank of an entangled pure state resource cannot be less than the Schmidt rank
of the unitary. We prove that if these ranks are equal the resource must be
uniformly (maximally) entangled: equal nonzero Schmidt coefficients. Higher
rank resources can have less entanglement: we have found numerical examples of
Schmidt rank 2 unitaries which can be deterministically implemented, by either
SEP or LOCC, using an entangled resource of two qutrits with less than one ebit
of entanglement.Comment: 7 pages Revte
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