Campus & alumni news

Boston University Medicine was published by the Boston University Medical Campus, and presented stories on events and topics of interest to members of the BU Medical Campus community. It followed the discontinued publication Centerscope as Boston University Medicine from 1991-2005, and was continued as Campus & Alumni News from 2006-2013 before returning to the title Boston University Medicine from 2014-present

Chiral gravity in two dimensions

It is shown that conformal matter with c_{\ssc L}\not=c_{\ssc R} can be consistently coupled to two-dimensional `frame' gravity. The theory is quantized, following David, and Distler and Kawai, using the derivation of their {\it ansatz} due to Mavromatos and Miramontes, and D'Hoker and Kurzepa. New super-selection rules are found by requiring SL(2,{\bf C}) invariance of correlation functions on the plane. There is no analogue of the $c=1$ barrier found in non-chiral non-critical strings. A non-critical heterotic string is constructed---it has 744 states in its spectrum, transforming in the adjoint representation of $(E_8)^3.$ Correlation functions are calculated in this example.Comment: 19 pages, iassns-hep-92-19/McGill/92-2

The Infrared Einstein Ring in the Gravitational Lens MG1131+0456 and the Death of the Dusty Lens Hypothesis

We have obtained and modeled new NICMOS images of the lens system MG1131+0456, which show that its lens galaxy is an H=18.6 mag, transparent, early-type galaxy at a redshift of about z_l = 0.85; it has a major axis effective radius R_e=0.68+/-0.05 arcsec, projected axis ratio b/a=0.77+/-0.02, and major axis PA=60+/-2 degrees. The lens is the brightest member of a group of seven galaxies with similar R-I and I-H colors, and the two closest group members produce sufficient tidal perturbations to explain the ring morphology. The host galaxy of the MG1131+0456 source is a z_s > 2 ERO (``extremely red object'') which is lensed into optical and infrared rings of dramatically different morphologies. These differences imply a strongly wavelength-dependent source morphology that could be explained by embedding the host in a larger, dusty disk. At 1.6 micron (H), the ring is spectacularly luminous, with a total observed flux of H=17.4 mag and a de-magnified flux of 19.3 mag, corresponding to a 1-2L_* galaxy at the probable source redshift of z_s > 2. Thus, it is primarily the stellar emission of the radio source host galaxy that produces the overall colors of two of the reddest radio lenses, MG1131+0456 and B~1938+666, aided by the suppression of optical AGN emission by dust in the source galaxy. The dusty lens hypothesis -- that many massive early-type galaxies with 0.2 < z_l < 1.0 have large, uniform dust opacities -- is ruled out.Comment: 27 pages, 8 COLOR figures, submitted to ApJ. Black and white version available at http://cfa-www.harvard.edu/castle

Relativistic Hydrodynamics with General Anomalous Charges

We consider the hydrodynamic regime of gauge theories with general triangle anomalies, where the participating currents may be global or gauged, abelian or non-abelian. We generalize the argument of arXiv:0906.5044, and construct at the viscous order the stress-energy tensor, the charge currents and the entropy current.Comment: 13 pages, Revte

Combined Diagram: A Graphical Representation of Combination Evaporation Rates

ABSTRACT Combination methods estimate the partition of sensible and latent heat fluxes at the surface by combining the surface energy balance equation with the transfer equations for temperature and water vapor in the atmospheric surface layer. This paper presents a diagram that graphically depicts the main assumptions and steps of the method. Potential, apparent potential, and actual evaporation rates are visually explained with the diagram. Using a linearized saturation water content relation, the diagram permits the derivation of many of the combination evaporation results by means of geometrical analysis. The diagram should be helpful in the teaching and understanding of the combination methodology

Dark Matter and Pseudo-flat Directions in Weakly Coupled SUSY Breaking Sectors

We consider candidates for dark matter in models of gauge mediated supersymmetry breaking, in which the supersymmetry breaking sector is weakly coupled and calculable. Such models typically contain classically flat directions, that receive one-loop masses of a few TeV. These pseudo-flat directions provide a new mechanism to account for the cold dark matter relic abundance. We discuss also the possibility of heavy gravitino dark matter in such models.Comment: 16 pages, 2 figures. v2: comments, refs adde

Analysis of Lung Metastases in Patients with Primary Extremity Sarcoma

Purpose: To investigate the incidence, radiographic findings, and the time course for the appearence of lung metastases from primary extremity sarcoma