62,145 research outputs found
Narrative Quilts and Quilted Narratives: The Art of Faith Ringgold and Alice Walker
There have been two main streams of influence on Chicano artists aside from the obvious one that is the result of their artistic training, education and development in the United States. The primary influence came from Mexico, first during the colonial period in the form of New Spanish art and architecture, and then in modem times provided by the Mexican muralists through their work and their use of pre-Columbian art. The New Spanish materials formed the nucleus for the second stream of influence composed of the various manifestations of religious folk art found primarily in the Southwest
Holographic renormalisation group flows and renormalisation from a Wilsonian perspective
From the Wilsonian point of view, renormalisable theories are understood as
submanifolds in theory space emanating from a particular fixed point under
renormalisation group evolution. We show how this picture precisely applies to
their gravity duals. We investigate the Hamilton-Jacobi equation satisfied by
the Wilson action and find the corresponding fixed points and their
eigendeformations, which have a diagonal evolution close to the fixed points.
The relevant eigendeformations are used to construct renormalised theories. We
explore the relation of this formalism with holographic renormalisation. We
also discuss different renormalisation schemes and show that the solutions to
the gravity equations of motion can be used as renormalised couplings that
parametrise the renormalised theories. This provides a transparent connection
between holographic renormalisation group flows in the Wilsonian and
non-Wilsonian approaches. The general results are illustrated by explicit
calculations in an interacting scalar theory in AdS space.Comment: 63 pages. Minor changes and references added. Matches JHEP versio
The effect of opening up ANWR to drilling on the current price of oil
The Effect of Opening up ANWR to Drilling on the Current Price of Oil R. Morris Coats and Gary M. PecquetEveryone knows that oil discovered today, perhaps in the Alaskan National Wildlife Refuge (ANWR), has no effect on prices until that oil hits the market. For instance, on its website, the Democratic Policy Committee, (http://democrats.senate.gov/~dpc/pubs/107-1-72.html) states that “it will require seven to twelve years from approval before there is any oil production from the ANWR area. Therefore, production in ANWR will have no impact on current or short-term gasoline and oil supplies and prices.” While this is something that everyone seems to know, it is a case that the theory held by everyone just happens to be wrong. Since future prices are expected to be lower, future profits are also lower, so the value of oil not produced now, but held for future sales, is lower, making it more profitable to go ahead and produce and sell now instead of waiting for future profits. Using oil now reduces the amount of oil available for the future, which involves the opportunity cost of forgone future profits, which are sometime called the marginal user costs or scarcity rents. In this paper, we use simple two-period models to show that if an amount of newly discovered oil is significant enough to reduce prices in the future, any drop in future prices reduces the future profitability of oil, reducing the marginal user costs of oil now. That reduction in the marginal user costs reduces the current price of oil just as if there were a reduction in the marginal costs of extracting oil now. We explore the effects of the reduction in marginal user costs in the competitive or price-taker case as well as the price-searcher case, where a monopolist or dominant supplier responds to a substantial discovery by another seller, but where the discovery will not contribute to production for some years to come. In both cases, we find that oil that is expected to reach the market at some time in the future has an immediate impact on oil prices. Topic Area: Q4 EnergyANWR; resource discovery; timing of price impact; speculation
A Nonthermal Radio Filament Connected to the Galactic Black Hole?
Using the Very Large Array, we have investigated a non-thermal radio filament
(NTF) recently found very near the Galactic black hole and its radio
counterpart, SgrA*. While this NTF -- the Sgr A West Filament (SgrAWF) --
shares many characteristics with the population of NTFs occupying the central
few hundred parsecs of the Galaxy, the SgrAWF has the distinction of having an
orientation and sky location that suggest an intimate physical connection to
SgrA*. We present 3.3 and 5.5 cm images constructed using an innovative
methodology that yields a very high dynamic range, providing an unprecedentedly
clear picture of the SgrAWF. While the physical association of the SgrAWF with
SgrA* is not unambiguous, the images decidedly evoke this interesting
possibility. Assuming that the SgrAWF bears a physical relationship to SgrA*,
we examine the potential implications. One is that SgrA* is a source of
relativistic particles constrained to diffuse along ordered local field lines.
The relativistic particles could also be fed into the local field by a
collimated outflow from SgrA*, perhaps driven by the Poynting flux accompanying
the black hole spin in the presence of a magnetic field threading the event
horizon. Second, we consider the possibility that the SgrAWF is the
manifestation of a low-mass-density cosmic string that has become anchored to
the black hole. The simplest form of these hypotheses would predict that the
filament be bi-directional, whereas the SgrAWF is only seen on one side of
SgrA*, perhaps because of the dynamics of the local medium.Comment: 9 pages, 4 figures, accepted for ApJ Letter
A New Perspective of the Radio Bright Zone at The Galactic Center: Feedback from Nuclear Activities
New observations of Sgr A have been carried out with the VLA using the
broadband (2 GHz) continuum mode at 5.5 GHz, covering the central 30 pc region
of the RBZ at the Galactic center. Using the MS-MFS algorithms in CASA, we have
imaged Sgr A with a resolution of 1", achieving an rms 8 Jy/beam, and a
dynamic range 100,000:1.The radio image is compared with X-ray, CN
emission-line and Paschen- images obtained using Chandra, SMA and
HST/NICMOS, respectively. We discuss several prominent radio features. The "Sgr
A West Wings" extend 5 pc from the NW and SE tips of the ionized "Mini-spiral"
in Sgr A West to positions located 2.9 and 2.4 arc min to the NW and SE of Sgr
A*, respectively. The NW wing, along with several other prominent features,
including the "NW Streamers", form an elongated radio lobe (NW lobe), oriented
nearly perpendicular to the Galactic plane. This radio lobe, with a size of
14.4 pc x 7.3 pc, has a known X-ray counterpart. A row of three thermally
emitting rings is observed in the NW lobe. A field containing numerous
amorphous radio blobs extends for a distance of ~2 arc min beyond the tip of
the SE wing; these features coincide with the SE X-ray lobe. Most of the
amorphous radio blobs in the NW and SE lobes have Paschen-
counterparts, suggesting that a shock interaction of ambient gas concentrations
with a collimated nuclear wind (outflow) that may be driven by radiation force
from the central star cluster within the CND. Finally, we remark on a prominent
radio feature located within the shell of the Sgr A East SNR. Because this
feature -- the "Sigma Front" -- correlates well in shape and orientation with
the nearby edge of the CND, we propose that it is a reflected shock wave
resulting from the impact of the Sgr A East blast wave on the CND.Comment: 18 pages, 9 figures, ApJ accepte
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