730 research outputs found
Convergence and Stability of the Inverse Scattering Series for Diffuse Waves
We analyze the inverse scattering series for diffuse waves in random media.
In previous work the inverse series was used to develop fast, direct image
reconstruction algorithms in optical tomography. Here we characterize the
convergence, stability and approximation error of the serie
The averaged null energy condition and difference inequalities in quantum field theory
Recently, Larry Ford and Tom Roman have discovered that in a flat cylindrical
space, although the stress-energy tensor itself fails to satisfy the averaged
null energy condition (ANEC) along the (non-achronal) null geodesics, when the
``Casimir-vacuum" contribution is subtracted from the stress-energy the
resulting tensor does satisfy the ANEC inequality. Ford and Roman name this
class of constraints on the quantum stress-energy tensor ``difference
inequalities." Here I give a proof of the difference inequality for a minimally
coupled massless scalar field in an arbitrary two-dimensional spacetime, using
the same techniques as those we relied on to prove ANEC in an earlier paper
with Robert Wald. I begin with an overview of averaged energy conditions in
quantum field theory.Comment: 20 page
Continuity of the measure of the spectrum for quasiperiodic Schrodinger operators with rough potentials
We study discrete quasiperiodic Schr\"odinger operators on \ell^2(\zee)
with potentials defined by -H\"older functions. We prove a general
statement that for and under the condition of positive Lyapunov
exponents, measure of the spectrum at irrational frequencies is the limit of
measures of spectra of periodic approximants. An important ingredient in our
analysis is a general result on uniformity of the upper Lyapunov exponent of
strictly ergodic cocycles.Comment: 15 page
A Bishop-Phelps-Bollobas Type Theorem for uniform algegras
This paper is devoted to showing that Asplund operators with range in a uniform Banach algebra have
the Bishop¿Phelps¿Bollobas property, i.e., they are approximated by norm attaining Asplund operators
at the same time that a point where the approximated operator almost attains its norm is approximated
by a point at which the approximating operator attains it. To prove this result we use the weak*-to-norm
fragmentability of weak*-compact subsets of the dual of Asplund spaces and we need to observe a Urysohn type result producing peak complex-valued functions in uniform algebras that are small outside a given open set and whose image is inside a Stolz region.This research was partially supported by MEC and FEDER projects MTM2008-05396 and MTM2011-25377. The research of the second author was also partially supported by Generalitat Valenciana (GV/2010/036), and by Universidad Politecnica de Valencia (project PAID-06-09-2829).Cascales, B.; Guirao Sánchez, AJ.; Kadets, V. (2013). A Bishop-Phelps-Bollobas Type Theorem for uniform algegras. Advances in Mathematics. 240:370-382. https://doi.org/10.1016/j.aim.2013.03.005S37038224
Time Asymmetric Quantum Physics
Mathematical and phenomenological arguments in favor of asymmetric time
evolution of micro-physical states are presented.Comment: Tex file with 2 figure
Revisiting the ‘Great Levelling’: the limits of Piketty’s Capital and Ideology for understanding the rise of late 20th century inequality
In Capital and Ideology, Thomas Piketty returns to questions of historical inequality, not merely to fill in the gaps in the earlier, widely circulated and impactful Capital in the 21st Century, but to undertake a far more ambitious and nuanced project. Critics (Bhambra and Holmwood 2017; Moeller 2015) pointed out that in the previous book, Piketty’s consideration of the role of high concentrations wealth on inequality focused largely on a handful of relatively wealthy countries (the US, UK, France, Germany and Japan). More importantly, it did not consider the political and economic relationships, forged by European colonization and the trans-Atlantic slave trade, that helped create lasting inequalities in wealth, status, education and life expectancy around the globe. These oversights corresponded to significant methodological gaps, in which inequalities defined by social status and identity, including gender, race and caste, were largely left out of considerations that centred around economic and material disparities. Yet these different forms of inequalities are intimately connected, as gender wage gaps and racial wealth gaps in different parts of the world attest
Schooling and Poor Children in 19th-Century America
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68138/2/10.1177_000276429203500307.pd
The theory and method of comparative area studies
Though many now downplay the tension between area studies and disciplinary political science, there has been little substantive guidance on how to accomplish complementarity between their respective approaches. This article seeks to develop the idea of comparative area studies (CAS) as a rubric that maintains the importance of regional knowledge while contributing to general theory building using inductive intra-regional, cross-regional, inter-regional comparison. Treating regions as theoretically-grounded analytical categories, rather than inert or innate geographical entities, can help inform both quantitative and qualitative attempts to build general theory.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
The association between biochemical control and cardiovascular risk factors in acromegaly
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