scispace - formally typeset
Search or ask a question
Institution

International School for Advanced Studies

EducationTrieste, Friuli-Venezia Giulia, Italy
About: International School for Advanced Studies is a education organization based out in Trieste, Friuli-Venezia Giulia, Italy. It is known for research contribution in the topics: Galaxy & Dark matter. The organization has 3751 authors who have published 13433 publications receiving 588454 citations. The organization is also known as: SISSA & Scuola Internazionale Superiore di Studi Avanzati.


Papers
More filters
Journal ArticleDOI
TL;DR: A simple inflationary model characterized by a scale factor which grows like Sapprox.t/sup p/, with p a constant greater than one, which is called power-law inflation (PLI), and considers the constraints on this model coming from the requirement of solving the horizon, flatness, ''good'' reheating, and ''convenient'' perturbation-spectrum problems.
Abstract: The outstanding cosmological problems (horizon, flatness, . . .) which may be solved by the usual inflationary models may also find a solution in the frame of a ``generalized'' inflationary cosmology which is characterized by a suitable phase of accelerated expansion. The usual exponential growth of the scale factor S is just a particular case of such a general idea. Following this line of thought, we study in some detail a simple inflationary model characterized by a scale factor which grows like S\ensuremath{\sim}${t}^{p}$, with p a constant greater than one, which we call power-law inflation (PLI). Some properties of PLI have been analyzed, in different contexts, also by other authors. We consider the constraints on this model coming from the requirement of solving the horizon, flatness, ``good'' reheating, and ``convenient'' perturbation-spectrum problems. In order to obtain the perturbation spectrum when re-entering the horizon during the Friedmann phase, we extend to PLI the gauge-invariant approach developed by Bardeen et al. for the usual inflationary models. We find that the above constraints can be suitably satisfied. Finally, we outline possible connections between PLI and particular inflationary models which have recently been proposed.

803 citations

Journal ArticleDOI
Alain Abergel1, Peter A. R. Ade2, Nabila Aghanim1, M. I. R. Alves1  +307 moreInstitutions (66)
TL;DR: In this article, the authors presented an all-sky model of dust emission from the Planck 857, 545 and 353 GHz, and IRAS 100 micron data.
Abstract: This paper presents an all-sky model of dust emission from the Planck 857, 545 and 353 GHz, and IRAS 100 micron data. Using a modified black-body fit to the data we present all-sky maps of the dust optical depth, temperature, and spectral index over the 353-3000 GHz range. This model is a tight representation of the data at 5 arcmin. It shows variations of the order of 30 % compared with the widely-used model of Finkbeiner, Davis, and Schlegel. The Planck data allow us to estimate the dust temperature uniformly over the whole sky, providing an improved estimate of the dust optical depth compared to previous all-sky dust model, especially in high-contrast molecular regions. An increase of the dust opacity at 353 GHz, tau_353/N_H, from the diffuse to the denser interstellar medium (ISM) is reported. It is associated with a decrease in the observed dust temperature, T_obs, that could be due at least in part to the increased dust opacity. We also report an excess of dust emission at HI column densities lower than 10^20 cm^-2 that could be the signature of dust in the warm ionized medium. In the diffuse ISM at high Galactic latitude, we report an anti-correlation between tau_353/N_H and T_obs while the dust specific luminosity, i.e., the total dust emission integrated over frequency (the radiance) per hydrogen atom, stays about constant. The implication is that in the diffuse high-latitude ISM tau_353 is not as reliable a tracer of dust column density as we conclude it is in molecular clouds where the correlation of tau_353 with dust extinction estimated using colour excess measurements on stars is strong. To estimate Galactic E(B-V) in extragalactic fields at high latitude we develop a new method based on the thermal dust radiance, instead of the dust optical depth, calibrated to E(B-V) using reddening measurements of quasars deduced from Sloan Digital Sky Survey data.

768 citations

Journal ArticleDOI
13 May 1999-Nature
TL;DR: The theory accounts in a general way for the quarter-power allometric scaling of living organisms and predicts scaling relations applicable to all efficient transportation networks, which is verified from observational data on the river drainage basins.
Abstract: Many biological processes, from cellular metabolism to population dynamics, are characterized by allometric scaling (power-law) relationships between size and rate1,2,3,4,5,6,7,8,9,10 An outstanding question is whether typical allometric scaling relationships—the power-law dependence of a biological rate on body mass—can be understood by considering the general features of branching networks serving a particular volume Distributed networks in nature stem from the need for effective connectivity11, and occur both in biological systems such as cardiovascular and respiratory networks1,2,3,4,5,6,7,8 and plant vascular and root systems1,9,10, and in inanimate systems such as the drainage network of river basins12 Here we derive a general relationship between size and flow rates in arbitrary networks with local connectivity Our theory accounts in a general way for the quarter-power allometric scaling of living organisms1,2,3,4,5,6,7,8,9,10, recently derived8 under specific assumptions for particular network geometries It also predicts scaling relations applicable to all efficient transportation networks, which we verify from observational data on the river drainage basins Allometric scaling is therefore shown to originate from the general features of networks irrespective of dynamical or geometric assumptions

758 citations

Journal ArticleDOI
28 Aug 2003-Nature
TL;DR: A theoretical framework for the unified neutral theory of biodiversity and an analytical solution for the distribution of the RSA both in the metacommunity (Fisher's log series) and in the local community, where there are fewer rare species.
Abstract: The theory of island biogeography asserts that an island or a local community approaches an equilibrium species richness as a result of the interplay between the immigration of species from the much larger metacommunity source area and local extinction of species on the island (local community). Hubbell generalized this neutral theory to explore the expected steady-state distribution of relative species abundance (RSA) in the local community under restricted immigration. Here we present a theoretical framework for the unified neutral theory of biodiversity and an analytical solution for the distribution of the RSA both in the metacommunity (Fisher's log series) and in the local community, where there are fewer rare species. Rare species are more extinction-prone, and once they go locally extinct, they take longer to re-immigrate than do common species. Contrary to recent assertions, we show that the analytical solution provides a better fit, with fewer free parameters, to the RSA distribution of tree species on Barro Colorado Island, Panama, than the lognormal distribution.

734 citations

Journal ArticleDOI
TL;DR: In this paper, coherent atomic oscillations between two weakly coupled Bose-Einstein condensates are discussed, where the weak link is provided by a laser barrier in a (possibly asymmetric) double-well trap or by Raman coupling between two Condensates in different hyperfine levels.
Abstract: We discuss the coherent atomic oscillations between two weakly coupled Bose-Einstein condensates. The weak link is provided by a laser barrier in a (possibly asymmetric) double-well trap or by Raman coupling between two condensates in different hyperfine levels. The boson Josephson junction (BJJ) dynamics is described by the two-mode nonlinear Gross-Pitaevskii equation that is solved analytically in terms of elliptic functions. The BJJ, being a neutral, isolated system, allows the investigations of dynamical regimes for the phase difference across the junction and for the population imbalance that are not accessible with superconductor Josephson junctions (SJJ's). These include oscillations with either or both of the following properties: (i) the time-averaged value of the phase is equal to $\ensuremath{\pi} (\ensuremath{\pi}$-phase oscillations); (ii) the average population imbalance is nonzero, in states with macroscopic quantum self-trapping. The (nonsinusoidal) generalization of the SJJ ac and plasma oscillations and the Shapiro resonance can also be observed. We predict the collapse of experimental data (corresponding to different trap geometries and the total number of condensate atoms) onto a single universal curve for the inverse period of oscillations. Analogies with Josephson oscillations between two weakly coupled reservoirs of ${}^{3}\mathrm{He}\ensuremath{-}B$ and the internal Josephson effect in ${}^{3}\mathrm{He}\ensuremath{-}A$ are also discussed.

728 citations


Authors

Showing all 3802 results

NameH-indexPapersCitations
Sabino Matarrese155775123278
G. de Zotti154718121249
J. González-Nuevo144500108318
Matt J. Jarvis144106485559
Carlo Baccigalupi137518104722
L. Toffolatti13637695529
Michele Parrinello13363794674
Marzio Nessi129104678641
Luigi Danese12839492073
Lidia Smirnova12794475865
Michele Pinamonti12684669328
David M. Alexander12565260686
Davide Maino12441088117
Dipak Munshi12436584322
Peter Onyisi11469460392
Network Information
Related Institutions (5)
Max Planck Society
406.2K papers, 19.5M citations

90% related

Weizmann Institute of Science
54.5K papers, 3M citations

88% related

University of Paris-Sud
52.7K papers, 2.1M citations

88% related

Brookhaven National Laboratory
39.4K papers, 1.7M citations

88% related

École Polytechnique
39.2K papers, 1.2M citations

87% related

Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202322
202279
2021656
2020714
2019712
2018622