41 research outputs found
Deformed symmetries from quantum relational observables
Deformed Special Relativity (DSR) is a candidate phenomenological theory to describe the Quantum Gravitational (QG) semi-classical regime. A possible interpretation of DSR can be derived from the notion of deformed reference frame. Observables in (quantum) General Relativity can be constructed from (quantum) reference frame â a physical observable is then a relation between a system of interest and the reference frame. We present a toy model and study an example of such quantum relational observables. We show how the intrinsic quantum nature of the reference frame naturally leads to a deformation of the symmetries, comforting DSR to be a good candidate to describe the QG semi-classical regime
Using association rule mining to enrich semantic concepts for video retrieval
In order to achieve true content-based information retrieval on video we should analyse and index video with
high-level semantic concepts in addition to using user-generated tags and structured metadata like title, date,
etc. However the range of such high-level semantic concepts, detected either manually or automatically,
usually limited compared to the richness of information content in video and the potential vocabulary of
available concepts for indexing. Even though there is work to improve the performance of individual concept
classiïŹers, we should strive to make the best use of whatever partial sets of semantic concept occurrences
are available to us. We describe in this paper our method for using association rule mining to automatically
enrich the representation of video content through a set of semantic concepts based on concept co-occurrence
patterns. We describe our experiments on the TRECVid 2005 video corpus annotated with the 449 concepts
of the LSCOM ontology. The evaluation of our results shows the usefulness of our approach
Quantum reference frames and deformed symmetries
In the context of constrained quantum mechanics, reference systems are used
to construct relational observables that are invariant under the action of the
symmetry group. Upon measurement of a relational observable, the reference
system undergoes an unavoidable measurement "back-action" that modifies its
properties. In a quantum-gravitational setting, it has been argued that such a
back-action may produce effects that are described at an effective level as a
form of deformed (or doubly) special relativity. We examine this possibility
using a simple constrained system that has been extensively studied in the
context of quantum information. While our conclusions support the idea of a
symmetry deformation, they also reveal a host of other effects that may be
relevant to the context of quantum gravity, and could potentially conceal the
symmetry deformation.Comment: 11 pages, revtex. Comments are welcom
A comparison of the Bravyi-Kitaev and Jordan-Wigner transformations for the quantum simulation of quantum chemistry
The ability to perform classically intractable electronic structure
calculations is often cited as one of the principal applications of quantum
computing. A great deal of theoretical algorithmic development has been
performed in support of this goal. Most techniques require a scheme for mapping
electronic states and operations to states of and operations upon qubits. The
two most commonly used techniques for this are the Jordan-Wigner transformation
and the Bravyi-Kitaev transformation. However, comparisons of these schemes
have previously been limited to individual small molecules. In this paper we
discuss resource implications for the use of the Bravyi-Kitaev mapping scheme,
specifically with regard to the number of quantum gates required for
simulation. We consider both small systems which may be simulatable on
near-future quantum devices, and systems sufficiently large for classical
simulation to be intractable. We use 86 molecular systems to demonstrate that
the use of the Bravyi-Kitaev transformation is typically at least approximately
as efficient as the canonical Jordan-Wigner transformation, and results in
substantially reduced gate count estimates when performing limited circuit
optimisations.Comment: 46 pages, 11 figure
Actionable Recourse in Linear Classification
Machine learning models are increasingly used to automate decisions that
affect humans - deciding who should receive a loan, a job interview, or a
social service. In such applications, a person should have the ability to
change the decision of a model. When a person is denied a loan by a credit
score, for example, they should be able to alter its input variables in a way
that guarantees approval. Otherwise, they will be denied the loan as long as
the model is deployed. More importantly, they will lack the ability to
influence a decision that affects their livelihood.
In this paper, we frame these issues in terms of recourse, which we define as
the ability of a person to change the decision of a model by altering
actionable input variables (e.g., income vs. age or marital status). We present
integer programming tools to ensure recourse in linear classification problems
without interfering in model development. We demonstrate how our tools can
inform stakeholders through experiments on credit scoring problems. Our results
show that recourse can be significantly affected by standard practices in model
development, and motivate the need to evaluate recourse in practice.Comment: Extended version. ACM Conference on Fairness, Accountability and
Transparency [FAT2019
The Genotype Specific Competitive Ability Does Not Correlate with Infection in Natural Daphnia magna Populations
Different evolutionary hypotheses predict a correlation between the fitness of a genotype in the absence of infection and the likelihood to become infected. The cost of resistance hypothesis predicts that resistant genotypes pay a cost of being resistant and are less fit in the absence of parasites. The inbreeding-infection hypothesis predicts that the susceptible individuals are less fit due to inbreeding depression.Here we tested if a host's natural infection status was associated with its fitness. First, we experimentally confirmed that cured but formerly infected Daphnia magna are genetically more susceptible to reinfections with Octosporea bayeri than naturally uninfected D. magna. We then collected from each of 22 populations both uninfected and infected D. magna genotypes. All were treated against parasites and kept in their asexual phase. We estimated their relative fitness in an experiment against a tester genotype and in another experiment in direct competition. Consistently, we found no difference in competitive abilities between uninfected and cured but formerly infected genotypes. This was the case both in the presence as well as in the absence of sympatric parasites during the competition trials.Our data do not support the inbreeding-infection hypothesis. They also do not support a cost of resistance, however ignoring other parasite strains or parasite species. We suggest as a possible explanation for our results that resistance genes might segregate largely independently of other fitness associated genes in this system
Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species
Background: The prevailing paradigm of host-parasite evolution is that arms races lead to increasing specialisation via genetic adaptation. Insect herbivores are no exception and the majority have evolved to colonise a small number of closely related host species. Remarkably, the green peach aphid, Myzus persicae, colonises plant species across 40 families and single M. persicae clonal lineages can colonise distantly related plants. This remarkable ability makes M. persicae a highly destructive pest of many important crop species. Results: To investigate the exceptional phenotypic plasticity of M. persicae, we sequenced the M. persicae genome and assessed how one clonal lineage responds to host plant species of different families. We show that genetically identical individuals are able to colonise distantly related host species through the differential regulation of genes belonging to aphid-expanded gene families. Multigene clusters collectively upregulate in single aphids within two days upon host switch. Furthermore, we demonstrate the functional significance of this rapid transcriptional change using RNA interference (RNAi)-mediated knock-down of genes belonging to the cathepsin B gene family. Knock-down of cathepsin B genes reduced aphid fitness, but only on the host that induced upregulation of these genes. Conclusions: Previous research has focused on the role of genetic adaptation of parasites to their hosts. Here we show that the generalist aphid pest M. persicae is able to colonise diverse host plant species in the absence of genetic specialisation. This is achieved through rapid transcriptional plasticity of genes that have duplicated during aphid evolution