4,825 research outputs found
Initial conditions for inflation and the energy scale of SUSY-breaking from the (nearly) gaussian sky
We show how general initial conditions for small field inflation can be
obtained in multi-field models. This is provided by non-linear angular friction
terms in the inflaton that provide a phase of non-slow-roll inflation before
the slow-roll inflation phase. This in turn provides a natural mechanism to
star small-field slow-roll at nearly zero velocity for arbitrary initial
conditions. We also show that there is a relation between the scale of SUSY
breaking sqrt (f) and the amount of non-gaussian fluctuations generated by the
inflaton. In particular, we show that in the local non-gaussian shape there
exists the relation sqrt (f) = 10^{13} GeV sqrt (f_NL). With current
observational limits from Planck, and adopting the minimum amount of
non-gaussian fluctuations allowed by single-field inflation, this provides a
very tight constraint for the SUSY breaking energy scale sqrt (f) = 3-7 x
10^{13} GeV at 95% confidence. Further limits, or detection, from next year's
Planck polarisation data will further tighten this constraint by a factor of
two. We highlight that the key to our approach is to identify the inflaton with
the scalar component of the goldstino superfield. This superfield is universal
and implements the dynamics of SUSY breaking as well as superconformal
breaking.Comment: Invited talk at the BW2013 meetin
Solution-processed organic devices developed by a novel cost-effective patterning technique based on electrical erosion
Application of arc erosion to the patterning of metallic contacts in organic devices is presented. A home-made systems and details of the working principles are described. Advantages and drawbacks of this novel technology are discussed
The international law gaze: Marshall Island v United Kingdom
The International Court of Justice recently bowed to nuclear weapons States and disappointed the rest of the international community. Forty-two years after the Courtâs astonishing decision in declaring the dispute on nuclear tests between New Zealand and France terminated (Nuclear Test Case (New Zealand v. France), [1974] I.C.J. Rep. 458, at [54]), a new chapter on the reluctance of the Court to deal with nuclear weapons took place in its judgment of 5 October 2016 on Preliminary Objections in Obligations Concerning Negotiations Relating to Cessation of the Nuclear Arms Race and to Nuclear Disarmament (Marshall Islands v United Kingdom). There, the Court declared that it lacked jurisdiction, since there was no dispute between the parties. (Marshall Islands v UK, at [59])
Class-Weighted Convolutional Features for Visual Instance Search
Image retrieval in realistic scenarios targets large dynamic datasets of
unlabeled images. In these cases, training or fine-tuning a model every time
new images are added to the database is neither efficient nor scalable.
Convolutional neural networks trained for image classification over large
datasets have been proven effective feature extractors for image retrieval. The
most successful approaches are based on encoding the activations of
convolutional layers, as they convey the image spatial information. In this
paper, we go beyond this spatial information and propose a local-aware encoding
of convolutional features based on semantic information predicted in the target
image. To this end, we obtain the most discriminative regions of an image using
Class Activation Maps (CAMs). CAMs are based on the knowledge contained in the
network and therefore, our approach, has the additional advantage of not
requiring external information. In addition, we use CAMs to generate object
proposals during an unsupervised re-ranking stage after a first fast search.
Our experiments on two public available datasets for instance retrieval,
Oxford5k and Paris6k, demonstrate the competitiveness of our approach
outperforming the current state-of-the-art when using off-the-shelf models
trained on ImageNet. The source code and model used in this paper are publicly
available at http://imatge-upc.github.io/retrieval-2017-cam/.Comment: To appear in the British Machine Vision Conference (BMVC), September
201
Powering AGNs with super-critical black holes
We propose a novel mechanism for powering the central engines of Active
Galactic Nuclei through super-critical (type II) black hole collapse. In this
picture, ~ of material collapsing at relativistic speeds can
trigger a gravitational shock, which can eject a large percentage of the
collapsing matter at relativistic speeds, leaving behind a "light" black hole.
In the presence of a poloidal magnetic field, the plasma collimates along two
jets, and the associated electron synchrotron radiation can easily account for
the observed radio luminosities, sizes and durations of AGN jets. For Lorentz
factors of order 100 and magnetic fields of a few hundred , synchrotron
electrons can shine for yrs, producing jets of sizes of order 100 kpc.
This mechanism may also be relevant for Gamma Ray Bursts and, in the absence of
magnetic field, supernova explosions.Comment: 4 pages, 1 figur
Multi-variate joint PDF for non-Gaussianities: exact formulation and generic approximations
We provide an exact expression for the multi-variate joint probability
distribution function of non-Gaussian fields primordially arising from local
transformations of a Gaussian field. This kind of non-Gaussianity is generated
in many models of inflation. We apply our expression to the non- Gaussianity
estimation from Cosmic Microwave Background maps and the halo mass function
where we obtain analytical expressions. We also provide analytic approximations
and their range of validity. For the Cosmic Microwave Background we give a fast
way to compute the PDF which is valid up to 7{\sigma} for fNL values (both true
and sampled) not ruled out by current observations, which consists of
expressing the PDF as a combination of bispectrum and trispectrum of the
temperature maps. The resulting expression is valid for any kind of
non-Gaussianity and is not limited to the local type. The above results may
serve as the basis for a fully Bayesian analysis of the non-Gaussianity
parameter.Comment: Matches accepted verion to JCAP; conclusions unchaged, extra
references adde
Estudio semiĂłtico del pasquĂn virtual en las elecciones presidenciales de MĂ©xico 2012
El PasquĂn es un sustantivo masculino un cartel, cedulĂłn que es un medio de comunicaciĂłn masivo que llega a un gran nĂșmero de personas. Los pasquines han sido de gran ayuda para dar informaciĂłn oportuna y no requerida. Su importancia radica en la escala con la que pueden llegar y ser conocidos por el pĂșblico
The bias of weighted dark matter halos from peak theory
We give an analytical form for the weighted correlation function of peaks in
a Gaussian random field. In a cosmological context, this approach strictly
describes the formation bias and is the main result here. Nevertheless, we show
its validity and applicability to the evolved cosmological density field and
halo field, using Gaussian random field realisations and dark matter N-body
numerical simulations. Using this result from peak theory we compute the bias
of peaks (and dark matter halos) and show that it reproduces results from the
simulations at the level. Our analytical formula for the
bias predicts a scale-dependent bias with two characteristics: a broad band
shape which, however, is most affected by the choice of weighting scheme and
evolution bias, and a more robust, narrow feature localised at the BAO scale,
an effect that is confirmed in simulations. This scale-dependent bias smooths
the BAO feature but, conveniently, does not move it. We provide a simple
analytic formula to describe this effect. We envision that our analytic
solution will be of use for galaxy surveys that exploit galaxy clustering.Comment: Submitted to MNRA
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