3,938 research outputs found
A Characterization of Deterministic Sampling Patterns for Low-Rank Matrix Completion
Low-rank matrix completion (LRMC) problems arise in a wide variety of
applications. Previous theory mainly provides conditions for completion under
missing-at-random samplings. This paper studies deterministic conditions for
completion. An incomplete matrix is finitely rank- completable
if there are at most finitely many rank- matrices that agree with all its
observed entries. Finite completability is the tipping point in LRMC, as a few
additional samples of a finitely completable matrix guarantee its unique
completability. The main contribution of this paper is a deterministic sampling
condition for finite completability. We use this to also derive deterministic
sampling conditions for unique completability that can be efficiently verified.
We also show that under uniform random sampling schemes, these conditions are
satisfied with high probability if entries per column are
observed. These findings have several implications on LRMC regarding lower
bounds, sample and computational complexity, the role of coherence, adaptive
settings and the validation of any completion algorithm. We complement our
theoretical results with experiments that support our findings and motivate
future analysis of uncharted sampling regimes.Comment: This update corrects an error in version 2 of this paper, where we
erroneously assumed that columns with more than r+1 observed entries would
yield multiple independent constraint
Marriage and care of a spouse with dementia: a cross-cultural study Brazil-Portugal
This study aimed to analyze the meaning of marriage and care of the spouse from the perspective of Brazilian and Portuguese caregivers of elderly people with Alzheimer Disease (AD). Twelve women participated in the study, being the sample obtained by convenience using the snowball technique. We used a questionnaire and a semi-structured interview, data were analyzed by the Bardin content analysis technique. The results pointed out that although the cultural differences between Brazil and Portugal, some meanings related to marriage and care of the spouse in the context of AD were similar for Brazilian and Portuguese wives. Despite marital changes related to dementia, most wives felt well performing their role of caregiver, perhaps because among other variables, this is a task traditionally and culturally expected to be performed by women of both countries.info:eu-repo/semantics/publishedVersio
Hamilton-Jacobi formalism for Linearized Gravity
In this work we study the theory of linearized gravity via the
Hamilton-Jacobi formalism. We make a brief review of this theory and its
Lagrangian description, as well as a review of the Hamilton-Jacobi approach for
singular systems. Then we apply this formalism to analyze the constraint
structure of the linearized gravity in instant and front-form dynamics.Comment: To be published in Classical and Quantum Gravit
Deterministic Conditions for Subspace Identifiability from Incomplete Sampling
Consider a generic -dimensional subspace of , , and
suppose that we are only given projections of this subspace onto small subsets
of the canonical coordinates. The paper establishes necessary and sufficient
deterministic conditions on the subsets for subspace identifiability.Comment: To appear in Proc. of IEEE ISIT, 201
Comments on regularization ambiguities and local gauge symmetries
We study the regularization ambiguities in an exact renormalized
(1+1)-dimensional field theory. We show a relation between the regularization
ambiguities and the coupling parameters of the theory as well as their role in
the implementation of a local gauge symmetry at quantum level.Comment: Latex 2e, 4 pages. To appear in Modern Physics Letters
Flux-dynamics associated with the Second Magnetisation Peak in iron-pnictide Ba_{1-x}K_xFe_2As_2
We report on isofield magnetic relaxation data on a single crystal of
with superconducting transition temperature = 32.7 K
which exhibit the so called fish-tail effect. A surface map of the
superconducting transition temperature shows that the superconducting
properties are close to homogeneous across the sample. Magnetic relaxation
data, M(t), was used to obtain the activation energy U(M) in order to study
different vortex dynamics regimes. Results of this analysis along with time
dependent measurements as a function of field and temperature extended to the
reversible region of some M(H) curves demonstrate that the irreversibility as
well the second magnetization peak position, , are time dependent and
controlled by plastic motion of the vortex state. In the region delimited by a
characteristic field Hon (well below ), and , the vortex dynamics is
controlled by collective pinning. For fields below Hon the activation energy,
, increases with field as expected for collective pinning, but the pinning
mechanism is likely to be in the single vortex limit.Comment: 8 pages, 8 figures, one tabl
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