43 research outputs found
Peaks in the Hartle-Hawking Wave Function from Sums over Topologies
Recent developments in ``Einstein Dehn filling'' allow the construction of
infinitely many Einstein manifolds that have different topologies but are
geometrically close to each other. Using these results, we show that for many
spatial topologies, the Hartle-Hawking wave function for a spacetime with a
negative cosmological constant develops sharp peaks at certain calculable
geometries. The peaks we find are all centered on spatial metrics of constant
negative curvature, suggesting a new mechanism for obtaining local homogeneity
in quantum cosmology.Comment: 16 pages,LaTeX, no figures; v2: some changes coming from revision of
a math reference: wave function peaks sharp but not infinite; v3: added
paragraph in intro on interpretation of wave functio
Designing Ecosystems of Intelligence from First Principles
This white paper lays out a vision of research and development in the field
of artificial intelligence for the next decade (and beyond). Its denouement is
a cyber-physical ecosystem of natural and synthetic sense-making, in which
humans are integral participants -- what we call ''shared intelligence''. This
vision is premised on active inference, a formulation of adaptive behavior that
can be read as a physics of intelligence, and which inherits from the physics
of self-organization. In this context, we understand intelligence as the
capacity to accumulate evidence for a generative model of one's sensed world --
also known as self-evidencing. Formally, this corresponds to maximizing
(Bayesian) model evidence, via belief updating over several scales: i.e.,
inference, learning, and model selection. Operationally, this self-evidencing
can be realized via (variational) message passing or belief propagation on a
factor graph. Crucially, active inference foregrounds an existential imperative
of intelligent systems; namely, curiosity or the resolution of uncertainty.
This same imperative underwrites belief sharing in ensembles of agents, in
which certain aspects (i.e., factors) of each agent's generative world model
provide a common ground or frame of reference. Active inference plays a
foundational role in this ecology of belief sharing -- leading to a formal
account of collective intelligence that rests on shared narratives and goals.
We also consider the kinds of communication protocols that must be developed to
enable such an ecosystem of intelligences and motivate the development of a
shared hyper-spatial modeling language and transaction protocol, as a first --
and key -- step towards such an ecology.Comment: 23+18 pages, one figure, one six page appendi
Identification of a Novel Class of Farnesylation Targets by Structure-Based Modeling of Binding Specificity
Farnesylation is an important post-translational modification catalyzed by farnesyltransferase (FTase). Until recently it was believed that a C-terminal CaaX motif is required for farnesylation, but recent experiments have revealed larger substrate diversity. In this study, we propose a general structural modeling scheme to account for peptide binding specificity and recapitulate the experimentally derived selectivity profile of FTase in vitro. In addition to highly accurate recovery of known FTase targets, we also identify a range of novel potential targets in the human genome, including a new substrate class with an acidic C-terminal residue (CxxD/E). In vitro experiments verified farnesylation of 26/29 tested peptides, including both novel human targets, as well as peptides predicted to tightly bind FTase. This study extends the putative range of biological farnesylation substrates. Moreover, it suggests that the ability of a peptide to bind FTase is a main determinant for the farnesylation reaction. Finally, simple adaptation of our approach can contribute to more accurate and complete elucidation of peptide-mediated interactions and modifications in the cell
A case of pediatric Henoch-Schonlein purpura and thrombosis of spermatic veins
The authors report a case of thrombosis of the spermatic veins associated with Henoch-Schonlein purpura mimicking an acute scrotum, which responded to a low-molecular-weight heparin treatment
Sophisticated Affective Inference: Simulating Anticipatory Affective Dynamics of Imagining Future Events
In this paper, we combine sophisticated and deep-parametric active inference to create an agent whose affective states change as a consequence of its Bayesian beliefs about how possible future outcomes will affect future beliefs. To achieve this, we augment Markov Decision Processes with a Bayes-adaptive deep-temporal tree search that is guided by a free energy functional which recursively scores counterfactual futures. Our model reproduces the common phenomenon of rumination over a situation until unlikely, yet aversive and arousing situations emerge in one’s imagination. As a proof of concept, we show how certain hyperparameters give rise to neurocognitive dynamics that characterise imagination-induced anxiety