7,243 research outputs found
Quantum Effective Action in Spacetimes with Branes and Boundaries
We construct quantum effective action in spacetime with branes/boundaries.
This construction is based on the reduction of the underlying Neumann type
boundary value problem for the propagator of the theory to that of the much
more manageable Dirichlet problem. In its turn, this reduction follows from the
recently suggested Neumann-Dirichlet duality which we extend beyond the tree
level approximation. In the one-loop approximation this duality suggests that
the functional determinant of the differential operator subject to Neumann
boundary conditions in the bulk factorizes into the product of its Dirichlet
counterpart and the functional determinant of a special operator on the brane
-- the inverse of the brane-to-brane propagator. As a byproduct of this
relation we suggest a new method for surface terms of the heat kernel
expansion. This method allows one to circumvent well-known difficulties in heat
kernel theory on manifolds with boundaries for a wide class of generalized
Neumann boundary conditions. In particular, we easily recover several lowest
order surface terms in the case of Robin and oblique boundary conditions. We
briefly discuss multi-loop applications of the suggested Dirichlet reduction
and the prospects of constructing the universal background field method for
systems with branes/boundaries, analogous to the Schwinger-DeWitt technique.Comment: LaTeX, 25 pages, final version, to appear in Phys. Rev.
Steeped in Rhetoric: Digital Populism and the Tea Party Movement
Though politically disparate and hard to quantify, one of the binding elements of the Tea Party Movement is Internet Communication Technology, or new media. Social media, online discussion boards, blogs, and other forms of new media constitute a veritable component of the discourse among its members. From the whispering confederation of conservative bloggers in its beginning stages, to the relatively quick transition into a social media powerhouse, the Tea Party fits into the category of dissident social movements in a new way than movements past, in that web-based communication is a staple of the movement. Also, the Tea Party's "Web 2.0" identity intersects with a tradition of populism, combining new media communication with rhetoric depicting the Tea Party as "common" people pitted against "elitist" enemies of the country. The populist sentiments within the Tea Party reflect a wider understanding about the role of technology in fostering democracy, and "restoring" the republic back to its "core values." Tea Partiers, then, could be described as "Digital Populists," historically situated among the histories of other American populist moments, but understanding new media technology as a new way to shape political discourse. Throughout this project, then, my aim is to link populist rhetoric with technological determinism, using the Tea Party's new media ecology as a case study. The first chapter provides historical examples of populist rhetorical frameworks informing the relationship between technology and society; Chapter 2 is a case study of three Tea Party websites; and Chapter 3 is a theoretical reflection on the data that analyzes how the Tea Party's engagement with new media fits into broader conversations about technology and democracy. At the core of this project is an inquiry into how technology works in our everyday lives. My analysis questions the presumption that new media communication technology fosters a more democratic society. Specifically, I argue that, while steeped in rhetoric of technological liberation, revolution, and democracy, the Tea Party's approach to new media contributes less to a vibrant culture of democratic engagement, and more to a peculiar and unstable technological mythology in American culture
Higher Spin Gravitational Couplings and the Yang--Mills Detour Complex
Gravitational interactions of higher spin fields are generically plagued by
inconsistencies. We present a simple framework that couples higher spins to a
broad class of gravitational backgrounds (including Ricci flat and Einstein)
consistently at the classical level. The model is the simplest example of a
Yang--Mills detour complex, which recently has been applied in the mathematical
setting of conformal geometry. An analysis of asymptotic scattering states
about the trivial field theory vacuum in the simplest version of the theory
yields a rich spectrum marred by negative norm excitations. The result is a
theory of a physical massless graviton, scalar field, and massive vector along
with a degenerate pair of zero norm photon excitations. Coherent states of the
unstable sector of the model do have positive norms, but their evolution is no
longer unitary and their amplitudes grow with time. The model is of
considerable interest for braneworld scenarios and ghost condensation models,
and invariant theory.Comment: 19 pages LaTe
Further functional determinants
Functional determinants for the scalar Laplacian on spherical caps and
slices, flat balls, shells and generalised cylinders are evaluated in two,
three and four dimensions using conformal techniques. Both Dirichlet and Robin
boundary conditions are allowed for. Some effects of non-smooth boundaries are
discussed; in particular the 3-hemiball and the 3-hemishell are considered. The
edge and vertex contributions to the coefficient are examined.Comment: 25 p,JyTex,5 figs. on request
Effective action and heat kernel in a toy model of brane-induced gravity
We apply a recently suggested technique of the Neumann-Dirichlet reduction to
a toy model of brane-induced gravity for the calculation of its quantum
one-loop effective action. This model is represented by a massive scalar field
in the -dimensional flat bulk supplied with the -dimensional kinetic
term localized on a flat brane and mimicking the brane Einstein term of the
Dvali-Gabadadze-Porrati (DGP) model. We obtain the inverse mass expansion of
the effective action and its ultraviolet divergences which turn out to be
non-vanishing for both even and odd spacetime dimensionality . For the
massless case, which corresponds to a limit of the toy DGP model, we obtain the
Coleman-Weinberg type effective potential of the system. We also obtain the
proper time expansion of the heat kernel in this model associated with the
generalized Neumann boundary conditions containing second order tangential
derivatives. We show that in addition to the usual integer and half-integer
powers of the proper time this expansion exhibits, depending on the dimension
, either logarithmic terms or powers multiple of one quarter. This property
is considered in the context of strong ellipticity of the boundary value
problem, which can be violated when the Euclidean action of the theory is not
positive definite.Comment: LaTeX, 20 pages, new references added, typos correcte
End-to-End Localization and Ranking for Relative Attributes
We propose an end-to-end deep convolutional network to simultaneously
localize and rank relative visual attributes, given only weakly-supervised
pairwise image comparisons. Unlike previous methods, our network jointly learns
the attribute's features, localization, and ranker. The localization module of
our network discovers the most informative image region for the attribute,
which is then used by the ranking module to learn a ranking model of the
attribute. Our end-to-end framework also significantly speeds up processing and
is much faster than previous methods. We show state-of-the-art ranking results
on various relative attribute datasets, and our qualitative localization
results clearly demonstrate our network's ability to learn meaningful image
patches.Comment: Appears in European Conference on Computer Vision (ECCV), 201
Engineering Education for High-Ability Students
Over the course of their careers, engineers command a breadth and depth of knowledge from science, mathematics, society, politics, and economics that is needed for continuously updating their knowledge of the latest discoveries and advances. Driven by curiosity and enabled by rapid information technology, engineers are kept abreast of the latest advancements almost instantaneously. Today’s scientific knowledge is fluid and complex, yet these traits of engineering remain constant: the ability to define structure, plan, repeatedly evaluate, and align results to the initial objective. Engineering teachers need to facilitate their students’ ability to access information effectively and to apply it appropriately, as well as to foster a strong foundation in science and mathematics. Skill development in creativity, communication, and business acumen is the hallmark of an effective engineering education program and curriculum
Reasoned action approach to analyze differences in athletes\u27 physical activity during COVID-19
The purpose of this study was to examine the reasoned action approach (RAA) in relation to the impact of COVID-19 on college athletes’ physical activity (PA). Participants were college athletes (ages 18-22 years) who were involved in university, club, and/or intramural sport. The RAA constructs were measured for the three different types of PA behaviors. Statistical analyses included ANOVA and multiple regression analyses to evaluate the RAA determinants of PA intentions. Results partially supported theoretical expectations. All RAA constructs had an impact on perceived norms indicating a dominant influence. Remote social interaction/training during isolation periods are suggested to promote sustained conditioning among college athletes
Diffeomorphism invariant eigenvalue problem for metric perturbations in a bounded region
We suggest a method of construction of general diffeomorphism invariant
boundary conditions for metric fluctuations. The case of dimensional
Euclidean disk is studied in detail. The eigenvalue problem for the Laplace
operator on metric perturbations is reduced to that on -dimensional vector,
tensor and scalar fields. Explicit form of the eigenfunctions of the Laplace
operator is derived. We also study restrictions on boundary conditions which
are imposed by hermiticity of the Laplace operator.Comment: LATeX file, no figures, no special macro
Heat Kernel Expansion for Semitransparent Boundaries
We study the heat kernel for an operator of Laplace type with a
-function potential concentrated on a closed surface. We derive the
general form of the small asymptotics and calculate explicitly several
first heat kernel coefficients.Comment: 16 page
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