20,381 research outputs found
Landscape Predictions from Cosmological Vacuum Selection
In BP models with hundreds of fluxes, we compute the effects of cosmological
dynamics on the probability distribution of landscape vacua. Starting from
generic initial conditions, we find that most fluxes are dynamically driven
into a different and much narrower range of values than expected from landscape
statistics alone. Hence, cosmological evolution will access only a tiny
fraction of the vacua with small cosmological constant. This leads to a host of
sharp predictions. Unlike other approaches to eternal inflation, the
holographic measure employed here does not lead to "staggering", an excessive
spread of probabilities that would doom the string landscape as a solution to
the cosmological constant problem.Comment: 15 pages, 6 figures, v4 prd format, minor editin
Dewetting on porous media with aspiration
We consider a porous solid covered with a water film (or with a drop) in
situations where the liquid is pumped in, either spontaneously (if the porous
medium is hydrophilic) or mechanically (by an external pump). The dynamics of
dewetting is then strongly modified. We analyse a few major examples: a)
horizontal films, which break at a certain critical thickness, b) the "modified
Landau-Levich problem" where a porous plate moves up from a bath and carries a
film: aspiration towards the plate limits the height H reached by the film, c)
certain situation where the hysteresis of contact angles is important.Comment: Revised version: The analysis of the 'modified Landau-Levich problem'
(section 3) has been significantly revised. It is now treated as a singular
perturbation problem (using boundary-layer techniques), leading to a more
accurate physical pictur
Tensor Microwave Background Fluctuations for Large Multipole Order
We present approximate formulas for the tensor BB, EE, TT, and TE multipole
coefficients for large multipole order l. The error in using the approximate
formula for the BB multipole coefficients is less than cosmic variance for
l>10. These approximate formulas make various qualitative properties of the
calculated multipole coefficients transparent: specifically, they show that,
whatever values are chosen for cosmological parameters, the tensor EE multipole
coefficients will always be larger than the BB coefficients for all l>15, and
that these coefficients will approach each other for l<<100. These
approximations also make clear how these multipole coefficients depend on
cosmological parameters.Comment: 19 pages, 9 figures, accepted for publication in Phys. Rev. D,
references and comments on earlier work on the subject added, cosmetic
modification of figure
Inspection of fine wires simplified by capillary tube wire holder
Capillary tube wire holder provides a mount for fine wires for photomicrographs. The holder is mounted in a stainless steel tube and cast in a transparent casting material. It protects and permits easy location of the wire
Context Attentive Bandits: Contextual Bandit with Restricted Context
We consider a novel formulation of the multi-armed bandit model, which we
call the contextual bandit with restricted context, where only a limited number
of features can be accessed by the learner at every iteration. This novel
formulation is motivated by different online problems arising in clinical
trials, recommender systems and attention modeling. Herein, we adapt the
standard multi-armed bandit algorithm known as Thompson Sampling to take
advantage of our restricted context setting, and propose two novel algorithms,
called the Thompson Sampling with Restricted Context(TSRC) and the Windows
Thompson Sampling with Restricted Context(WTSRC), for handling stationary and
nonstationary environments, respectively. Our empirical results demonstrate
advantages of the proposed approaches on several real-life datasetsComment: IJCAI 201
Strong screening in the plum pudding model
We study a generalized Thomson problem that appears in several condensed
matter settings: identical point-charge particles can penetrate inside a
homogeneously charged sphere, with global electro-neutrality. The emphasis is
on scaling laws at large Coulombic couplings, and deviations from mean-field
behaviour, by a combination of Monte Carlo simulations and an analytical
treatment within a quasi-localized charge approximation, which provides
reliable predictions. We also uncover a local overcharging phenomenon driven by
ionic correlations alone
Simultaneous Perturbation Algorithms for Batch Off-Policy Search
We propose novel policy search algorithms in the context of off-policy, batch
mode reinforcement learning (RL) with continuous state and action spaces. Given
a batch collection of trajectories, we perform off-line policy evaluation using
an algorithm similar to that by [Fonteneau et al., 2010]. Using this
Monte-Carlo like policy evaluator, we perform policy search in a class of
parameterized policies. We propose both first order policy gradient and second
order policy Newton algorithms. All our algorithms incorporate simultaneous
perturbation estimates for the gradient as well as the Hessian of the
cost-to-go vector, since the latter is unknown and only biased estimates are
available. We demonstrate their practicality on a simple 1-dimensional
continuous state space problem
- …
