2,234 research outputs found
Coolant passage heat transfer with rotation, a progress report
The objective of this 36-month experimental and analytical program is to develop a heat transfer and pressure drop database, computational fluid dynamic techniques, and correlations for multipass rotating coolant passages with and without flow turbulators. The experimental effort will be focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines so that the effects of Coriolis and buoyancy forces on the coolant side flow can be rationally included in the design of turbine blades
Irrelevant Interactions without Composite Operators - A Remark on the Universality of Second Order Phase Transitions
We study the critical behaviour of symmetric theory including
irrelevant terms of the form in the bare action,
where is the UV cutoff (corresponding e.g. to the inverse lattice
spacing for a spin system). The main technical tool is renormalization theory
based on the flow equations of the renormalization group which permits to
establish the required convergence statements in generality and rigour. As a
consequence the effect of irrelevant terms on the critical behaviour may be
studied to any order without using renormalization theory for composite
operators. This is a technical simplification and seems preferable from the
physical point of view. In this short note we restrict for simplicity to the
symmetry class of the Ising model, i.e. one component theory. The
method is general, however.Comment: 13 page
Large Momentum bounds from Flow Equations
We analyse the large momentum behaviour of 4-dimensional massive euclidean
Phi-4-theory using the flow equations of Wilson's renormalization group. The
flow equations give access to a simple inductive proof of perturbative
renormalizability. By sharpening the induction hypothesis we prove new and, as
it seems, close to optimal bounds on the large momentum behaviour of the
correlation functions. The bounds are related to what is generally called
Weinberg's theorem.Comment: 14 page
Singularity Cancellation in Fermion Loops through Ward Identities
Recently Neumayr and Metzner have shown that the connected N-point density-
correlation functions of the two-dimensional and the one-dimensional Fermi gas
at one-loop order generically vanish/are regular in the small momentum/small
energy-momentum limits. Their result is based on an explicit analysis in the
sequel of results of Feldman et al.[2]. In this note we use Ward identities to
give a proof of the same fact - in a considerably shortened and simplified way
- for any dimension of space.Comment: 11 pages, 2nd corrected and improved version, to appear in Ann. Henri
Poincar
Temperature Independent Renormalization of Finite Temperature Field Theory
We analyse 4-dimensional massive \vp^4 theory at finite temperature T in
the imaginary-time formalism. We present a rigorous proof that this quantum
field theory is renormalizable, to all orders of the loop expansion. Our main
point is to show that the counterterms can be chosen temperature independent,
so that the temperature flow of the relevant parameters as a function of
can be followed. Our result confirms the experience from explicit calculations
to the leading orders. The proof is based on flow equations, i.e. on the
(perturbative) Wilson renormalization group. In fact we will show that the
difference between the theories at T>0 and at T=0 contains no relevant terms.
Contrary to BPHZ type formalisms our approach permits to lay hand on
renormalization conditions and counterterms at the same time, since both appear
as boundary terms of the renormalization group flow. This is crucial for the
proof.Comment: 17 pages, typos and one footnote added, to appear in Ann.H.Poincar
Emotional Qualities of VR Space
The emotional response a person has to a living space is predominantly
affected by light, color and texture as space-making elements. In order to
verify whether this phenomenon could be replicated in a simulated environment,
we conducted a user study in a six-sided projected immersive display that
utilized equivalent design attributes of brightness, color and texture in order
to assess to which extent the emotional response in a simulated environment is
affected by the same parameters affecting real environments. Since emotional
response depends upon the context, we evaluated the emotional responses of two
groups of users: inactive (passive) and active (performing a typical daily
activity). The results from the perceptual study generated data from which
design principles for a virtual living space are articulated. Such a space, as
an alternative to expensive built dwellings, could potentially support new,
minimalist lifestyles of occupants, defined as the neo-nomads, aligned with
their work experience in the digital domain through the generation of emotional
experiences of spaces. Data from the experiments confirmed the hypothesis that
perceivable emotional aspects of real-world spaces could be successfully
generated through simulation of design attributes in the virtual space. The
subjective response to the virtual space was consistent with corresponding
responses from real-world color and brightness emotional perception. Our data
could serve the virtual reality (VR) community in its attempt to conceive of
further applications of virtual spaces for well-defined activities.Comment: 12 figure
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