2,057,710 research outputs found
Shear layer effects on the performance of an acoustic mirror microphone system
No full textDFVLR Forschungsbericht 79-30, Köl
Application of linear and nonlinear adaptive filters for the compensation of disturbances in the laminar boundary layer
No full textIn order to delay the laminar-turbulent transition in the boundary layer of airfoils the compensation of instability waves by artificially excited disturbances is studied. It turns out that also nonlinear processes occur in the spatial development of disturbances. This can be modeled by different types of nonlinear filter structures
R. F. and D. C. F. McEwin
No full text"SX11030 R.F. McEwin 2'14 Aust Field Reg Served In Darwin July 1941 - Jan 1943 _____ SX11081 D.C.F. McEwin 2'14 Aust Field Reg Served In Darwin July 1941 - Jan 1943"SX11030 R. F. McEwin 2'14 Australian Field Regiment Served In Darwin July 1941 - January 1943 ____ SX11081 D. C. F. McEwin 2'14 Australian Field Regiment Served In Darwin July 1941 - January 1943
On spectral measures for certain unitary representations of R. Thompson's group F
No full textThe Hilbert space H of backward renormalisation of an anyonic quantum spin chain affords a unitary representation of Thompson’s group F via local scale transformations. The group F is discrete and mysterious in many ways so the obvious questions of irreducibility and distinctness of these representations appear difficult and in a first step towards solving them we calculate the spectral measures of group elements in the representation. Given a vector in the canonical dense subspace of H we calculate the corresponding spectral measure and illustrate with some examples. To do this calculation we introduce the “essential part” (intimately related to the conjugacy class) of an element. The spectral measure for any vector in H is, apart from possibly finitely many eigenvalues, absolutely continuous with respect to
Lebesgue measure. The same considerations and results hold for the Brown-Thompson groups Fn (for which F = F2)
F & R, Ludmilla, Schutzmarke registriert
No full textF & R, LUDMILLA, SCHUTZMARKE REGISTRIERT
F & R, Ludmilla, Schutzmarke registriert ( -
Cosmological consequences of f(R) gravity
No full textreservedIn this thesis, we are focusing on a theory called f(R) gravity, obtained from modifications of General Relativity (GR) by adding higher powers of the Ricci scalar into the standard GR action. By introducing additional terms to the action, we aim to replicate the observed evolution of the Universe without being hindered by the problems of the existence of dark matter and dark energy and address some other interesting phenomena in the universe such as gravitational waves and cosmological perturbations.In this thesis, we are focusing on a theory called f(R) gravity, obtained from modifications of General Relativity (GR) by adding higher powers of the Ricci scalar into the standard GR action. By introducing additional terms to the action, we aim to replicate the observed evolution of the Universe without being hindered by the problems of the existence of dark matter and dark energy and address some other interesting phenomena in the universe such as gravitational waves and cosmological perturbations
F & R, Randl Ia Ia, Schutzmarke registriert
No full textF & R, RANDL IA IA, SCHUTZMARKE REGISTRIERT
F & R, Randl Ia Ia, Schutzmarke registriert ( -
Asymptotically Schwarzschild solutions in f (R) extension of general relativity
No full textWe address the question of how to build a class of f(R) extensions of General Relativity which are compatible with solar system experiments, without making any preliminary assumption on the properties of f. The aim is reached by perturbatively solving the modified Einstein equations around a Schwarzschild background and retrieving a posteriori the corresponding f(R). This turns out to be non analytical in R=0 and should be intended as the leading correction to the Einstein-Hilbert action in the low curvature limit. The parameters characterizing the f(R) class are then set by constraining the corrections to four different local tests with the observations. The result is a class of f(R) theories built up from a purely bottom-up approach and compatible with the local tests. At a more general level, this result can help constraining exact f(R) models working in Cosmology, since it provides the correct local limit. Further developments and possible extensions of the approach to Cosmology are also discussed
Redundant operators in the exact renormalisation group and in the f(R) approximation to asymptotic safety
No full textIn this paper we review the definition and properties of redundant operators in the exact renormalisation group. We explain why it is important to require them to be eigenoperators and why generically they appear only as a consequence of symmetries of the particular choice of renormalisation group equations. This clarifies when Newton’s constant and or the cosmological constant can be considered inessential. We then apply these ideas to the Local Potential Approximation and approximations of a similar spirit such as the f (R) approximation in the asymptotic safety programme in quantum gravity. We show that these approximations can break down if the fixed point does not support a ‘vacuum’ solution in the appropriate domain: all eigenoperators become redundant and the physical space of perturbations collapses to a point. We show that this is the case for the recently discovered lines of fixed points in the f (R) flow equations
R., F. an Herman Grimm (1 Brief)
No full textR., F. AN HERMAN GRIMM (1 BRIEF)
R., F. an Herman Grimm (1 Brief) (Br4220)
Brief 4220 (Br4220
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