Renormalization Group Approach to Spin Glass Systems

A renormalization group transformation suitable for spin glass models and, more generally, for disordered models, is presented. The procedure is non-standard in both the nature of the additional interactions and the coarse graining transformation, that is performed on the overlap probability measure (which is clearly non-Gibbsian). Universality classes are thus naturally defined on a large set of models, going from $\Z_2$ and Gaussian spin glasses to Ising and fully frustrated models, and others.Comment: 12 pages, 4 figure

Generation of the Primordial Magnetic Fields during Cosmological Reionization

We investigate the generation of magnetic field by the Biermann battery in cosmological ionization fronts, using new simulations of the reionization of the universe by stars in protogalaxies. Two mechanisms are primarily responsible for magnetogenesis: i) the breakout of I-fronts from protogalaxies, and ii) the propagation of I-fronts through the high density neutral filaments which are part of the cosmic web. The first mechanism is dominant prior to overlapping of ionized regions (z ~ 7), whereas the second continues to operate even after that epoch. However, after overlap the field strength increase is largely due to the gas compression occurring as cosmic structures form. As a consequence, the magnetic field at z ~ 5 closely traces the gas density, and it is highly ordered on megaparsec scales. The mean mass-weighted field strength is B_0 ~ 10^{-19} G in the simulation box. There is a relatively well-defined, nearly linear correlation between B_0 and the baryonic mass of virialized objects, with B_0 ~ 10^{-18} G in the most massive objects (M ~ 10^9 M_sun) in our simulations. This is a lower limit, as lack of numerical resolution prevents us from following small scale dynamical processes which could amplify the field in protogalaxies. Although the field strengths we compute are probably adequate as seed fields for a galactic dynamo, the field is too small to have had significant effects on galaxy formation, on thermal conduction, or on cosmic ray transport in the intergalactic medium. It could, however, be observed in the intergalactic medium through innovative methods based on analysis of gamma-ray burst photon arrival times.Comment: accepted for publication in ApJ. MPEG movies and color versions of figures are available at http://casa.colorado.edu/~gnedin/GALLERY/magfi_p.htm

Dust in active nuclei. I. Evidence for "anomalous" properties

We present observational evidences that dust in the circumnuclear region of AGNs has different properties than in the Galactic diffuse interstellar medium. By comparing the reddening of optical and infrared broad lines and the X-ray absorbing column density we find that the E(B-V)/N_H ratio is nearly always lower than Galactic by a factor ranging from ~3 up to ~100. Other observational results indicate that the Av/N_H ratio is significantly lower than Galactic in various classes of AGNs including intermediate type 1.8-1.9 Seyferts, hard X-ray selected and radio selected quasars, broad absorption line QSOs and grism selected QSOs. The lack of prominent absorption features at 9.7um (silicates) and at 2175A (carbon dip) in the spectra of Seyfert 2s and of reddened Seyfert 1s, respectively, add further evidence for dust in the circumnuclear region of AGNs being different from Galactic. These observational results indicate that the dust composition in the circumnuclear region of AGNs could be dominated by large grains, which make the extinction curve flatter, featureless and are responsible for the reduction of the E(B-V)/N_H and Av/N_H ratios. Regardless of the physical origin of these phenomena, the reduced dust absorption with respect to what expected from the gaseous column density should warn about a mismatch between the optical and the X-ray classification of the active galactic nuclei in terms of their obscuration.Comment: 9 pages, 3 figures, accepted for publication in A&

Challenging the empire

This paper considers how Paul Gilroy transformed hitherto dominant understandings of the relationship between race and class by developing an innovative account that foregrounded questions of racist oppression and collective resistance amid the organic crisis of British capitalism. The returns from this rethinking were profound in that he was able to make transparent both the structuring power of racism within the working class, and the necessity for autonomous black resistance. At the same time, significant lacunae in his account are identified, including the neglect of the episodic emergence of working-class anti-racism and the part played by socialists, particularly those of racialized minority descent in fashioning a major anti-racist social movement. The paper concludes with a lament for the disappearance of such work informed by a ‘Marxism without guarantees’ in the contemporary field of racism studies, and asks readers to consider the gains to be derived from such a re-engagement

Getting to know you: A novel approach in segmenting the ageing consumer market

This presentation was given as part of the Brunel Institute for Ageing Studies (BIAS) Annual Conference 2012 by Mona Shekarriz from the School of Engineering and Design at Brunel University. The 2nd annual conference was hosted at Brunel University on the 15th February 2012

後桃花源記 : 錦田-釜山藝術交流計劃 = In search of the peachland : art exchange project between Kam Tin and Busan

《後桃花源記》是一個涉及許多不同層次的交流計劃，當中包括來自韓國釜山和香港錦田的6個藝術單位(5位藝術家和1個藝術組合)、12位來自嶺南大學視覺研究系的學生。他們在2015年2月底前往韓國釜山參觀當地不同的藝術機構、藝術空間和藝術院校，與當中一些藝術家、策劃人和藝術學生對談。在交流過程中，大家都不難發現香港和釜山，這兩個遠離國家首都的沿海城市，所面對因城市發展和重建而產生的問題，均十分相似。在3月份，兩位來自釜山的藝術家:金大洪和金美英也進駐錦田。各藝術家與參與學生一起在錦田進行創作，並於2015年3月21和22日，把作品在地呈現，之後更以文獻方式在C&G藝術單位展示。 ‘In Search of the Peachland’ is an art exchange project involving many different layers of idea exchanges amongst different parties: including 6 art units from Kam Tin and Busan (5 artists and 1 artist group), 12 students from the Visual Studies Department of Lingnan University. They went to Busan for a field trip in the end of February, 2015, to visit different art organizations and art students in Busan. During the trip, it was not difficult to find out that both Hong Kong and Busan also encounter similar problems, when undergoing intensive urban development and redevelopment. After the field-trip, two artists from Busan: KIM Dae Hong and KIM Mi Young came to Hong Kong for an artist-in-residency period in Kam Tin during March. All participating artists from Kam Tin and Busan worked with students together in Kam Tin for various art projects, which were shown on-site on 21st and 22nd of March 2015. In the end, the documentation of the on-site projects was displayed at C&G Artpartment, for a month, for the public to have an overview of the whole exchange program.https://commons.ln.edu.hk/vs_student_work/1003/thumbnail.jp

Genetic Ties and the Family: The Impact of Paternity Testing on Parents and Children

Edited by Mark A. Rothstein, Thomas H. Murray, Gregory E. Kaebnick, and Mary Anderlik Majumder. 2005. Baltimore, Maryland: The John Hopkins University Press. Hardcover, $50.00 ISBN: 0-8018-8193-

Racism and anti-racism in Europe: a critical analysis of concepts and frameworks

The targets and expressions of racism vary across Europe. This article discusses the relevance of different descriptions and analyses of racism despite the different terms used in different countries such as ‘ethnic minority’, ‘foreigner’ or ‘black’ and different interpretations of which differences matter. It shows the significance of a cross-national European perspective on racism. There are important convergences across European countries in the discourses and practices of racism, particularly the distinction between ‘useful’ and ‘abusive’ migrants. A cross-European perspective can be an important inspiration for anti-racist struggles

Unifying models for X-ray selected and Radio selected BL Lac Objects

We discuss alternative interpretations of the differences in the Spectral Energy Distributions (SEDs) of BL Lacs found in complete Radio or X-ray surveys. A large body of observations in different bands suggests that the SEDs of BL Lac objects appearing in X-ray surveys differ from those appearing in radio surveys mainly in having a (synchrotron) spectral cut-off (or break) at much higher frequency. In order to explain the different properties of radio and X-ray selected BL Lacs Giommi and Padovani proposed a model based on a common radio luminosity function. At each radio luminosity, objects with high frequency spectral cut-offs are assumed to be a minority. Nevertheless they dominate the X-ray selected population due to the larger X-ray-to-radio-flux ratio. An alternative model explored here (reminiscent of the orientation models previously proposed) is that the X-ray luminosity function is "primary" and that at each X-ray luminosity a minority of objects has larger radio-to-X-ray flux ratio. The predictions of the two scenarios, computed via a Montecarlo technique, are compared with the observed properties of BL Lacs in the two samples extracted respectively from the 1 Jy radio survey and the Einstein Slew Survey. We show that both models can explain a number but not all the observed features. We then propose a completely new approach, based on the idea that the physical parameter which governs the shape of the SEDs, is (or is associated with) the bolometric luminosity. Assuming an empirical relation between spectral shape and luminosity we show that the observational properties of the two surveys can be reproduced at least with the same accuracy as the two previous models.Comment: 21 pages, when TeX-ed including tables (3) and figures (8). MNRAS latex. mn.sty and psfig.sty included. Accepted for pubblication in MNRAS. Also available at http://www.sissa.it/~fossati/pub_list.htm

Menopausal hormone use and ovarian cancer risk: individual participant meta-analysis of 52 epidemiological studies.

BACKGROUND: Half the epidemiological studies with information about menopausal hormone therapy and ovarian cancer risk remain unpublished, and some retrospective studies could have been biased by selective participation or recall. We aimed to assess with minimal bias the effects of hormone therapy on ovarian cancer risk. METHODS: Individual participant datasets from 52 epidemiological studies were analysed centrally. The principal analyses involved the prospective studies (with last hormone therapy use extrapolated forwards for up to 4 years). Sensitivity analyses included the retrospective studies. Adjusted Poisson regressions yielded relative risks (RRs) versus never-use. FINDINGS: During prospective follow-up, 12 110 postmenopausal women, 55% (6601) of whom had used hormone therapy, developed ovarian cancer. Among women last recorded as current users, risk was increased even with <5 years of use (RR 1·43, 95% CI 1·31-1·56; p<0·0001). Combining current-or-recent use (any duration, but stopped <5 years before diagnosis) resulted in an RR of 1·37 (95% CI 1·29-1·46; p<0·0001); this risk was similar in European and American prospective studies and for oestrogen-only and oestrogen-progestagen preparations, but differed across the four main tumour types (heterogeneity p<0·0001), being definitely increased only for the two most common types, serous (RR 1·53, 95% CI 1·40-1·66; p<0·0001) and endometrioid (1·42, 1·20-1·67; p<0·0001). Risk declined the longer ago use had ceased, although about 10 years after stopping long-duration hormone therapy use there was still an excess of serous or endometrioid tumours (RR 1·25, 95% CI 1·07-1·46, p=0·005). INTERPRETATION: The increased risk may well be largely or wholly causal; if it is, women who use hormone therapy for 5 years from around age 50 years have about one extra ovarian cancer per 1000 users and, if its prognosis is typical, about one extra ovarian cancer death per 1700 users. FUNDING: Medical Research Council, Cancer Research UK