3,149 research outputs found
Avoiding Wireheading with Value Reinforcement Learning
How can we design good goals for arbitrarily intelligent agents?
Reinforcement learning (RL) is a natural approach. Unfortunately, RL does not
work well for generally intelligent agents, as RL agents are incentivised to
shortcut the reward sensor for maximum reward -- the so-called wireheading
problem. In this paper we suggest an alternative to RL called value
reinforcement learning (VRL). In VRL, agents use the reward signal to learn a
utility function. The VRL setup allows us to remove the incentive to wirehead
by placing a constraint on the agent's actions. The constraint is defined in
terms of the agent's belief distributions, and does not require an explicit
specification of which actions constitute wireheading.Comment: Artificial General Intelligence (AGI) 201
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A physiological marker of recognition memory in adults with autism spectrum disorder? The Pupil Old/New Effect
This study investigated the pupil Old/New effect in individuals with Autism Spectrum Disorder (ASD) and typical development (TD). Participants studied verbal and visual meaningful and meaningless materials in black and white on a computer screen. Pupil sizes were measured while participants performed a Remember (episodic memory with context) /Know (semantic memory, no context) recognition memory test. ASD compared to TD individuals showed significantly reduced recognition rates for all materials. Both groups showed better memory for visual compared to verbal (picture superiority effect) and meaningful compared to meaningless materials. A pupil size ratio (pupil size for test item divided by baseline) for old (studied) and new (unstudied) materials indicated larger pupils for old compared to new materials only for the TD but not the ASD group. Pupil size in response to old versus new items was positively related to recognition accuracy, confirming that the pupil Old/New effect reflects a memory phenomenon in the ASD group. In addition, this study suggests an involvement of the noradrenergic neurotransmitter system in the abnormal hippocampal functioning in ASD. Implications of these findings as well as their underlying neurophysiology will be discussed in relation to current theories of memory in ASD
Nonlinear dynamics of giant resonances in atomic nuclei
The dynamics of monopole giant resonances in nuclei is analyzed in the
time-dependent relativistic mean-field model. The phase spaces of isoscalar and
isovector collective oscillations are reconstructed from the time-series of
dynamical variables that characterize the proton and neutron density
distributions. The analysis of the resulting recurrence plots and correlation
dimensions indicate regular motion for the isoscalar mode, and chaotic dynamics
for the isovector oscillations. Information-theoretic functionals identify and
quantify the nonlinear dynamics of giant resonances in quantum systems that
have spatial as well as temporal structure.Comment: 24 pages, RevTeX, 15 PS figures, submitted Phys. Rev.
Fission barriers in actinides in covariant density functional theory: the role of triaxiality
Relativistic mean field theory allowing for triaxial deformations is applied
for a systematic study of fission barriers in the actinide region. Different
pairing schemes are studied in details and it is shown that covariant density
functional theory is able to describe fission barriers on a level of accuracy
comparable with non-relativistic calculations, even with the best
phenomenological macroscopic+microscopic approaches. Triaxiality in the region
of the first saddle plays a crucial role in achieving that.Comment: 11 pages, 13 figure
Fission barriers in covariant density functional theory: extrapolation to superheavy nuclei
Systematic calculations of fission barriers allowing for triaxial deformation
are performed for even-even superheavy nuclei with charge number
using three classes of covariant density functional models. The softness of
nuclei in the triaxial plane leads to an emergence of several competing fission
pathes in the region of the inner fission barrier in some of these nuclei. The
outer fission barriers are considerably affected by triaxiality and octupole
deformation. General trends of the evolution of the inner and the outer fission
barrier heights are discussed as a function of the particle numbers.Comment: 24 pages, 8 tables, 12 figure
The Geometry of a -Deformed Phase Space
The geometry of the -deformed line is studied. A real differential
calculus is introduced and the associated algebra of forms represented on a
Hilbert space. It is found that there is a natural metric with an associated
linear connection which is of zero curvature. The metric, which is formally
defined in terms of differential forms, is in this simple case identifiable as
an observable.Comment: latex file, 26 pp, a typing error correcte
Comparison of TCGA and GENIE genomic datasets for the detection of clinically actionable alterations in breast cancer.
Whole exome sequencing (WES), targeted gene panel sequencing and single nucleotide polymorphism (SNP) arrays are increasingly used for the identification of actionable alterations that are critical to cancer care. Here, we compared The Cancer Genome Atlas (TCGA) and the Genomics Evidence Neoplasia Information Exchange (GENIE) breast cancer genomic datasets (array and next generation sequencing (NGS) data) in detecting genomic alterations in clinically relevant genes. We performed an in silico analysis to determine the concordance in the frequencies of actionable mutations and copy number alterations/aberrations (CNAs) in the two most common breast cancer histologies, invasive lobular and invasive ductal carcinoma. We found that targeted sequencing identified a larger number of mutational hotspots and clinically significant amplifications that would have been missed by WES and SNP arrays in many actionable genes such as PIK3CA, EGFR, AKT3, FGFR1, ERBB2, ERBB3 and ESR1. The striking differences between the number of mutational hotspots and CNAs generated from these platforms highlight a number of factors that should be considered in the interpretation of array and NGS-based genomic data for precision medicine. Targeted panel sequencing was preferable to WES to define the full spectrum of somatic mutations present in a tumor
Bimodality as a signal of Liquid-Gas phase transition in nuclei?
We use the HIPSE (Heavy-Ion Phase-Space Exploration) Model to discuss the
origin of the bimodality in charge asymmetry observed in nuclear reactions
around the Fermi energy. We show that it may be related to the important
angular momentum (spin) transferred into the quasi-projectile before secondary
decay. As the spin overcomes the critical value, a sudden opening of decay
channels is induced and leads to a bimodal distribution for the charge
asymmetry. In the model, it is not assigned to a liquid-gas phase transition
but to specific instabilities in nuclei with high spin. Therefore, we propose
to use these reactions to study instabilities in rotating nuclear droplets.Comment: 4 pages, 4 figures Accepted to PR
Localized form of Fock terms in nuclear covariant density functional theory
In most of the successful versions of covariant density functional theory in
nuclei, the Fock terms are not included explicitly, which leads to local
functionals and forms the basis of their widespread applicability at present.
However, it has serious consequences for the description of Gamow-Teller
resonances (GTR) and spin-dipole resonances (SDR) which can only be cured by
adding further phenomenological parameters. Relativistic Hartree-Fock models do
not suffer from these problems. They can successfully describe the GTR and SDR
as well as the isovector part of the Dirac effective mass without any
additional parameters. However, they are non-local and require considerable
numerical efforts. By the zero-range reduction and the Fierz transformation, a
new method is proposed to take into account the Fock terms in local
functionals, which retains the simplicity of conventional models and provides
proper descriptions of the spin-isospin channels and the Dirac masses.Comment: 6 pages, 4 figures, Phys. Rev. C in pres
Relativistic Hartree-Fock-Bogoliubov theory with Density Dependent Meson-Nucleon Couplings
Relativistic Hartree-Fock-Bogoliubov (RHFB) theory with density-dependent
meson-nucleon couplings is presented. The integro-differential RHFB equations
are solved by expanding the different components of the quasi-particle spinors
in the complete set of eigen-solutions of the Dirac equations with Woods-Saxon
potentials. Using the finite-range Gogny force D1S as an effective interaction
in the pairing channel, systematic RHFB calculations are performed for Sn
isotopes and N=82 isotones. It is demonstrated that an appropriate description
of both mean field and pairing effects can be obtained within RHFB theory with
finite range Gogny pairing forces. Better systematics are also found in the
regions from the stable to the neutron-rich side with the inclusion of Fock
terms, especially in the presence of -tensor couplings.Comment: 11 pages, 2 tables and 4 figure
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