64 research outputs found
On the APM power spectrum and the CMB anisotropy: Evidence for a phase transition during inflation?
Adams et al. (1997b) have noted that according to our current understanding
of the unification of fundamental interactions, there should have been phase
transitions associated with spontaneous symmetry breaking {\em during} the
inflationary era. This may have resulted in the breaking of scale-invariance of
the primordial density perturbation for brief periods. A possible such feature
was identified in the power spectrum of galaxy clustering in the APM survey at
the scale Mpc^{-1} and it was shown that the secondary acoustic
peaks in the power spectrum of the CMB anisotropy should consequently be
suppressed. We demonstrate that this prediction is confirmed by the recent
Boomerang and Maxima observations, which favour a step-like spectral feature in
the range Mpc^{-1}, independently of the similar previous
indication from the APM data. Such a spectral break enables an excellent fit to
both APM and CMB data with a baryon density consistent with the BBN value. It
also allows the possibility of a matter-dominated universe with zero
cosmological constant, which we show can now account for even the evolution of
the abundance of rich clusters.Comment: 11 pages (LaTeX, mn.sty) incl. 9 eps figs; small changes to match
version accepted for publication in MNRA
Further investigation of a relic neutralino as a possible origin of an annual-modulation effect in WIMP direct search
We analyze the annual-modulation effect, measured by the DAMA Collaboration
with the new implementation of a further two-years running, in the context of a
possible interpretation in terms of relic neutralinos. We impose over the set
of supersymmetric configurations, selected by the annual-modulation data, the
constraints derived from WIMP indirect measurements, and discuss the features
of the ensuing relic neutralinos. We critically discuss the sources of the main
theoretical uncertainties in the analysis of event rates for direct and
indirect WIMP searches.Comment: 29 pages, 12 figures, typeset with ReVTeX. In order to reduce size,
the version on the archive has low resolution figures. A full version of the
paper can be found at http://www.to.infn.it/~fornengo/papers
Formation and Evolution of Supermassive Black Holes
The correlation between the mass of supermassive black holes in galaxy nuclei
and the mass of the galaxy spheroids or bulges (or more precisely their central
velocity dispersion), suggests a common formation scenario for galaxies and
their central black holes. The growth of bulges and black holes can commonly
proceed through external gas accretion or hierarchical mergers, and are both
related to starbursts. Internal dynamical processes control and regulate the
rate of mass accretion. Self-regulation and feedback are the key of the
correlation. It is possible that the growth of one component, either BH or
bulge, takes over, breaking the correlation, as in Narrow Line Seyfert 1
objects. The formation of supermassive black holes can begin early in the
universe, from the collapse of Population III, and then through gas accretion.
The active black holes can then play a significant role in the re-ionization of
the universe. The nuclear activity is now frequently invoked as a feedback to
star formation in galaxies, and even more spectacularly in cooling flows. The
growth of SMBH is certainly there self-regulated. SMBHs perturb their local
environment, and the mergers of binary SMBHs help to heat and destroy central
stellar cusps. The interpretation of the X-ray background yields important
constraints on the history of AGN activity and obscuration, and the census of
AGN at low and at high redshifts reveals the downsizing effect, already
observed for star formation. History appears quite different for bright QSO and
low-luminosity AGN: the first grow rapidly at high z, and their number density
decreases then sharply, while the density of low-luminosity objects peaks more
recently, and then decreases smoothly.Comment: 31 pages, 13 figures, review paper for Astrophysics Update
Observing the First Stars and Black Holes
The high sensitivity of JWST will open a new window on the end of the
cosmological dark ages. Small stellar clusters, with a stellar mass of several
10^6 M_sun, and low-mass black holes (BHs), with a mass of several 10^5 M_sun
should be directly detectable out to redshift z=10, and individual supernovae
(SNe) and gamma ray burst (GRB) afterglows are bright enough to be visible
beyond this redshift. Dense primordial gas, in the process of collapsing from
large scales to form protogalaxies, may also be possible to image through
diffuse recombination line emission, possibly even before stars or BHs are
formed. In this article, I discuss the key physical processes that are expected
to have determined the sizes of the first star-clusters and black holes, and
the prospect of studying these objects by direct detections with JWST and with
other instruments. The direct light emitted by the very first stellar clusters
and intermediate-mass black holes at z>10 will likely fall below JWST's
detection threshold. However, JWST could reveal a decline at the faint-end of
the high-redshift luminosity function, and thereby shed light on radiative and
other feedback effects that operate at these early epochs. JWST will also have
the sensitivity to detect individual SNe from beyond z=10. In a dedicated
survey lasting for several weeks, thousands of SNe could be detected at z>6,
with a redshift distribution extending to the formation of the very first stars
at z>15. Using these SNe as tracers may be the only method to map out the
earliest stages of the cosmic star-formation history. Finally, we point out
that studying the earliest objects at high redshift will also offer a new
window on the primordial power spectrum, on 100 times smaller scales than
probed by current large-scale structure data.Comment: Invited contribution to "Astrophysics in the Next Decade: JWST and
Concurrent Facilities", Astrophysics & Space Science Library, Eds. H.
Thronson, A. Tielens, M. Stiavelli, Springer: Dordrecht (2008
Tuned Lamb Wave Excitation and Detection with Piezoelectric Wafer Active Sensors for Structural Health Monitoring
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Schools out : Adam Smith and pre-disciplinary international political economy
In this article, I argue that invocations of Adam Smith in international political economy (IPE) often reveal the influence therein of a disciplinary ontological disaggregation of economic and non-economic rationality, which I claim is obscured by the tendency to map its complex intellectual contours in terms of competing schools. I trace the origins of the disciplinary characterisation of Smith as the founder of IPE's liberal tradition to invocations of his thought by centrally important figures in the perceived Austrian, Chicago and German historical schools of economics, and reflect upon the significance to IPE of the reiteration of this portrayal by apparent members of its so-called American and British schools. I additionally contrast these interpretations to those put forward by scholars who seek to interpret IPE and Smith's contribution to it in pre-disciplinary terms, which I claim reflects a distinct ontology to that attributed to the British school of IPE with which their work is often associated. I therefore contend that reflection upon invocations of Smith's thought in IPE problematises the longstanding tendency to map its intellectual terrain in terms of competing schools, reveals that the disciplinary ontological consensus that informs this tendency impacts upon articulations of its core concerns and suggests that a pre-disciplinary approach offers an alternative lens through which such concerns might be more effectively framed
Galaxy bulges and their massive black holes: a review
With references to both key and oft-forgotten pioneering works, this article
starts by presenting a review into how we came to believe in the existence of
massive black holes at the centres of galaxies. It then presents the historical
development of the near-linear (black hole)-(host spheroid) mass relation,
before explaining why this has recently been dramatically revised. Past
disagreement over the slope of the (black hole)-(velocity dispersion) relation
is also explained, and the discovery of sub-structure within the (black
hole)-(velocity dispersion) diagram is discussed. As the search for the
fundamental connection between massive black holes and their host galaxies
continues, the competing array of additional black hole mass scaling relations
for samples of predominantly inactive galaxies are presented.Comment: Invited (15 Feb. 2014) review article (submitted 16 Nov. 2014). 590
references, 9 figures, 25 pages in emulateApJ format. To appear in "Galactic
Bulges", E. Laurikainen, R.F. Peletier, and D.A. Gadotti (eds.), Springer
Publishin
Finishing the euchromatic sequence of the human genome
The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
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