1,655 research outputs found
Combining Models of Approximation with Partial Learning
In Gold's framework of inductive inference, the model of partial learning
requires the learner to output exactly one correct index for the target object
and only the target object infinitely often. Since infinitely many of the
learner's hypotheses may be incorrect, it is not obvious whether a partial
learner can be modifed to "approximate" the target object.
Fulk and Jain (Approximate inference and scientific method. Information and
Computation 114(2):179--191, 1994) introduced a model of approximate learning
of recursive functions. The present work extends their research and solves an
open problem of Fulk and Jain by showing that there is a learner which
approximates and partially identifies every recursive function by outputting a
sequence of hypotheses which, in addition, are also almost all finite variants
of the target function.
The subsequent study is dedicated to the question how these findings
generalise to the learning of r.e. languages from positive data. Here three
variants of approximate learning will be introduced and investigated with
respect to the question whether they can be combined with partial learning.
Following the line of Fulk and Jain's research, further investigations provide
conditions under which partial language learners can eventually output only
finite variants of the target language. The combinabilities of other partial
learning criteria will also be briefly studied.Comment: 28 page
Review: Peering through a keyhole: liquid biopsy in primary and metastatic central nervous system tumours
Fibroid explants reveal a higher sensitivity against MDM2-inhibitor nutlin-3 than matching myometrium
<p>Abstract</p> <p>Background</p> <p>Spontaneous cessation of growth is a frequent finding in uterine fibroids. Increasing evidence suggests an important role of cellular senescence in this growth control. Deciphering the underlying mechanisms of growth control that can be expected not only to shed light on the biology of the tumors but also to identify novel therapeutic targets.</p> <p>Methods</p> <p>We have analyzed uterine leiomyomas and matching normal tissue for the expression of p14<sup>Arf </sup>and used explants to see if reducing the MDM2 activity using the small-molecule inhibitor nutlin-3 can induce p53 and activate genes involved in senescence and/or apoptosis. For these studies quantitative real-time RT-PCR, Western blots, and immunohistochemistry were used. Statistical analyses were performed using the student's <it>t </it>test.</p> <p>Results</p> <p>An in depth analysis of 52 fibroids along with matching myometrium from 31 patients revealed in almost all cases a higher expression of p14<sup>Arf </sup>in the tumors than in the matching normal tissue. In tissue explants, treatment with the MDM2 inhibitor nutlin-3 induced apoptosis as well as senescence as revealed by a dose-dependent increase of the expression of <it>BAX </it>as well as of <it>p21</it>, respectively. Simultaneously, the expression of the proliferation marker Ki-67 drastically decreased. Western-blot analysis identified an increase of the p53 level as the most likely reason for the increased activity of its downstream markers <it>BAX </it>and <it>p21</it>. Because as a rule fibroids express much higher levels of p14<sup>Arf</sup>, a major negative regulator of MDM2, than matching myometrium it was then analyzed if fibroids are more sensitive against nutlin-3 treatment than matching myometrium. We were able to show that in most fibroids analyzed a higher sensibility than that of matching myometrium was noted with a corresponding increase of the p53 immunopositivity of the fibroid samples compared to those from myometrium.</p> <p>Conclusions</p> <p>The results show that uterine fibroids represent a cell population of advanced cellular age compared to matching myometrium. Moreover, the data point to members of the p53-network as to potential novel therapeutic targets for the treatment of uterine fibroids.</p
Optical one-way quantum computing with a simulated valence-bond solid
One-way quantum computation proceeds by sequentially measuring individual
spins (qubits) in an entangled many-spin resource state. It remains a
challenge, however, to efficiently produce such resource states. Is it possible
to reduce the task of generating these states to simply cooling a quantum
many-body system to its ground state? Cluster states, the canonical resource
for one-way quantum computing, do not naturally occur as ground states of
physical systems. This led to a significant effort to identify alternative
resource states that appear as ground states in spin lattices. An appealing
candidate is a valence-bond-solid state described by Affleck, Kennedy, Lieb,
and Tasaki (AKLT). It is the unique, gapped ground state for a two-body
Hamiltonian on a spin-1 chain, and can be used as a resource for one-way
quantum computing. Here, we experimentally generate a photonic AKLT state and
use it to implement single-qubit quantum logic gates.Comment: 11 pages, 4 figures, 8 tables - added one referenc
Particle creation rate for dynamical black holes
We present the particle creation probability rate around a general black hole
as an outcome of quantum fluctuations. Using the uncertainty principle for
these fluctuation, we derive a new ultraviolet frequency cutoff for the
radiation spectrum of a dynamical black hole. Using this frequency cutoff, we
define the probability creation rate function for such black holes. We consider
a dynamical Vaidya model, and calculate the probability creation rate for this
case when its horizon is in a slowly evolving phase. Our results show that one
can expect the usual Hawking radiation emission process in the case of a
dynamical black hole when it has a slowly evolving horizon. Moreover,
calculating the probability rate for a dynamical black hole gives a measure of
when Hawking radiation can be killed off by an incoming flux of matter or
radiation. Our result strictly suggests that we have to revise the Hawking
radiation expectation for primordial black holes that have grown substantially
since they were created in the early universe. We also infer that this
frequency cut off can be a parameter that shows the primordial black hole
growth at the emission moment.Comment: 10 pages, 1 figure. The paper was rewritten in more clear
presentation and one more appendix is adde
Numerical Algebraic Geometry: A New Perspective on String and Gauge Theories
The interplay rich between algebraic geometry and string and gauge theories
has recently been immensely aided by advances in computational algebra.
However, these symbolic (Gr\"{o}bner) methods are severely limited by
algorithmic issues such as exponential space complexity and being highly
sequential. In this paper, we introduce a novel paradigm of numerical algebraic
geometry which in a plethora of situations overcomes these short-comings. Its
so-called 'embarrassing parallelizability' allows us to solve many problems and
extract physical information which elude the symbolic methods. We describe the
method and then use it to solve various problems arising from physics which
could not be otherwise solved.Comment: 36 page
The holographic principle
There is strong evidence that the area of any surface limits the information
content of adjacent spacetime regions, at 10^(69) bits per square meter. We
review the developments that have led to the recognition of this entropy bound,
placing special emphasis on the quantum properties of black holes. The
construction of light-sheets, which associate relevant spacetime regions to any
given surface, is discussed in detail. We explain how the bound is tested and
demonstrate its validity in a wide range of examples.
A universal relation between geometry and information is thus uncovered. It
has yet to be explained. The holographic principle asserts that its origin must
lie in the number of fundamental degrees of freedom involved in a unified
description of spacetime and matter. It must be manifest in an underlying
quantum theory of gravity. We survey some successes and challenges in
implementing the holographic principle.Comment: 52 pages, 10 figures, invited review for Rev. Mod. Phys; v2:
reference adde
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