5,424,013 research outputs found
Le potentiel de valorisation des cinémas de Sierre par l'association Ecran Total
Lâobjectif principal de cette Ă©tude est dâamener des rĂ©ponses concrĂštes Ă la question de recherche « comment valoriser Ă long terme les cinĂ©mas de Sierre afin dâattirer et de fidĂ©liser un public plus nombreux et dâatteindre les objectifs de rentabilitĂ© ?», dans le but de maintenir une politique culturelle pour la Ville de Sierre et dâassurer la pĂ©rennitĂ© des cinĂ©mas de la ville. Une des solutions envisagĂ©es est la fidĂ©lisation de la clientĂšle au travers divers Ă©vĂ©nements mis en place par lâassociation Ecran Total nouvellement crĂ©e (2013). Pour rĂ©aliser cette Ă©tude, trois axes analyses ont Ă©tĂ© choisis. PremiĂšrement, une analyse de marchĂ© a Ă©tĂ© effectuĂ©e afin de dĂ©peindre la situation dans laquelle le marchĂ© du cinĂ©ma Ă©volue et dâobserver les Ă©ventuelles menaces. Puis, une analyse concurrentielle de marchĂ© a permis dâentrevoir les stratĂ©gies des cinĂ©mas romands ainsi que celles des cinĂ©mas en dehors de la Suisse, concernant les animations et les Ă©vĂ©nements organisĂ©s afin dâaffiner le business modĂšle des cinĂ©mas sierrois. Pour finir, des entretiens qualitatifs ont Ă©tĂ© effectuĂ©s avec les diffĂ©rents acteurs, internes et externes, des cinĂ©mas sierrois, afin de positionner ces derniers par rapport aux autres cinĂ©mas. Les rĂ©sultats de cette Ă©tude ont permis de comprendre quelle Ă©tait la situation actuelle des cinĂ©mas sierrois et quelles pourraient ĂȘtre les pistes dâamĂ©lioration envisageables afin dâattirer et de fidĂ©liser la clientĂšle. De ces rĂ©sultats, un plan de communication comprenant diverses suggestions de scĂ©narii dâĂ©vĂ©nements a pu ĂȘtre dĂ©crit. Lâassociation Ecran Total est libre de sâen inspirer afin de proposer un ou plusieurs nouveaux Ă©vĂ©nements dans les salles sierroises
21-cm cosmology
Imaging the Universe during the first hundreds of millions of years remains
one of the exciting challenges facing modern cosmology. Observations of the
redshifted 21 cm line of atomic hydrogen offer the potential of opening a new
window into this epoch. This would transform our understanding of the formation
of the first stars and galaxies and of the thermal history of the Universe. A
new generation of radio telescopes is being constructed for this purpose with
the first results starting to trickle in. In this review, we detail the physics
that governs the 21 cm signal and describe what might be learnt from upcoming
observations. We also generalize our discussion to intensity mapping of other
atomic and molecular lines.Comment: 64 pages, 20 figures, submitted to Reports on Progress in Physics,
comments welcom
Detecting the 21 cm Forest in the 21 cm Power Spectrum
We describe a new technique for constraining the radio loud population of
active galactic nuclei at high redshift by measuring the imprint of 21 cm
spectral absorption features (the 21 cm forest) on the 21 cm power spectrum.
Using semi-numerical simulations of the intergalactic medium and a
semi-empirical source population we show that the 21 cm forest dominates a
distinctive region of -space, . By simulating
foregrounds and noise for current and potential radio arrays, we find that a
next generation instrument with a collecting area on the order of (such as the Hydrogen Epoch of Reionization Array) may
separately constrain the X-ray heating history at large spatial scales and
radio loud active galactic nuclei of the model we study at small ones. We
extrapolate our detectability predictions for a single radio loud active
galactic nuclei population to arbitrary source scenarios by analytically
relating the 21 cm forest power spectrum to the optical depth power spectrum
and an integral over the radio luminosity function.Comment: 20 pages, 17 figures, accepted for publication in MNRA
Accelerating the CM method
Given a prime q and a negative discriminant D, the CM method constructs an
elliptic curve E/\Fq by obtaining a root of the Hilbert class polynomial H_D(X)
modulo q. We consider an approach based on a decomposition of the ring class
field defined by H_D, which we adapt to a CRT setting. This yields two
algorithms, each of which obtains a root of H_D mod q without necessarily
computing any of its coefficients. Heuristically, our approach uses
asymptotically less time and space than the standard CM method for almost all
D. Under the GRH, and reasonable assumptions about the size of log q relative
to |D|, we achieve a space complexity of O((m+n)log q) bits, where mn=h(D),
which may be as small as O(|D|^(1/4)log q). The practical efficiency of the
algorithms is demonstrated using |D| > 10^16 and q ~ 2^256, and also |D| >
10^15 and q ~ 2^33220. These examples are both an order of magnitude larger
than the best previous results obtained with the CM method.Comment: 36 pages, minor edits, to appear in the LMS Journal of Computation
and Mathematic
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