6,302 research outputs found
How to resolve doxastic disagreement
How should an agent revise her epistemic state in the light of doxastic disagreement? The problems associated with answering this question arise under the assumption that an agent’s epistemic state is best represented by her degree of belief function alone. We argue that for modeling cases of doxastic disagreement an agent’s epistemic state is best represented by her confirmation commitments and the evidence available to her. Finally, we argue that given this position it is possible to provide an adequate answer to the question of how to rationally revise one’s epistemic state in the light of disagreemen
Evidence of Evidence as Higher Order Evidence
In everyday life and in science we acquire evidence of evidence and based on this new evidence we often change our epistemic states. An assumption underlying such practice is that the following EEE Slogan is correct: 'evidence of evidence is evidence' (Feldman 2007, p. 208). We suggest that evidence of evidence is best understood as higher-order evidence about the epistemic state of agents. In order to model evidence of evidence we introduce a new powerful framework for modelling epistemic states, Dyadic Bayesianism. Based on this framework, we then discuss characterizations of evidence of evidence and argue for one of them. Finally, we show that whether the EEE Slogan holds, depends on the specific kind of evidence of evidence
Inverse photoemission in strongly correlated electron systems
Based on exact results for small clusters of 2D t-J model we demonstrate the
existence of several distinct `channels' in its inverse photoemission (IPES)
spectrum. Hole-like quasiparticles can either be annihilated completely, or
leave behind a variable number of spin excitations, which formed the `dressing
cloud' of the annihilated hole. In the physical parameter regime the latter
processes carry the bulk of IPES weight and although the Fermi surface takes
the form of hole pockets, the distribution of spectal weight including these
`magnon-bands' in the IPES spectrum is reminiscent of free electrons. The
emerging scenario for Fermiology and spectral weight distribution is shown to
be consistent with photoemission, inverse photemission and de Haas--van Alphen
experiments on cuprate superconductors.Comment: Revtex file, 4 PRB pages + three figures appended as uu-encoded
postscript. Hardcopies of figures (or the entire manuscript) can also be
obtained by e-mail request to: [email protected]
Doping dependent quasiparticle band structure in cuprate superconductors
We present an exact diagonalization study of the single particle spectral
function in the so-called t-t'-t''-J model in 2D. As a key result, we find that
unlike the `pure' t-J model, hole doping leads to a major reconstruction of the
quasiparticle band structure near (pi,0): whereas for the undoped system the
quasiparticle states near (pi,0) are deep below the top of the band at
(pi/2,pi/2), hole doping shifts these states up to E_F, resulting in extended
flat band regions close to E_F and around (pi,0). This strong doping-induced
deformation can be directly compared to angle resolved photoemission results on
Sr_2 Cu Cl_2 O_2, underdoped Bi2212 and optimally doped Bi2212. We propose the
interplay of long range hopping and decreasing spin correlations as the
mechanism of this deformation.Comment: 4 pages, Revtex, with 4 embedded eps figures. Hardcopies of figures
(or the entire manuscript) can be obtained by e-mail request to
[email protected]
Inelastic Behaviour of Hybrid Steel/Concrete Column-to-Flat Slab Assemblages
The use of tubular columns in conjunction with reinforced concrete
flat slabs provides structurally
efficient solutions which avoid undesirable failure modes such as those associated with
shear. This thesis is concerned with the development of a tubular column-to-
flat slab connection
system that enables reliable performance under seismic loading conditions. During this
research a novel detail which features a gap around the column is proposed and developed;
hence only the structural steel shearhead establishes the connection. The exposed parts of
the shear arms (fuses) are designed to yield prior to punching shear failure, in a way that
utilises the favourable features of steel in terms of the response to seismically induced loads.
The proposed connection could serve as a primary lateral resisting system within all building
configurations in regions of low to moderate seismicity or as a secondary system in areas of
signi cant seismicity. In order to provide validation for the proposed details as well as associated
numerical and design procedures, a purpose-built rig which is suitable for large scale
testing of structural sub assemblages under combined gravity and uniaxial lateral loading,
has been designed and constructed, and subsequently employed for a number of tests. Test
results and numerical analyses are presented with respect to a conventional con guration,
as well as for the proposed, partially embedded connection. The latter is shown to offer
enhanced ductility compared with traditional forms. The results are used to demonstrate the
favourable inelastic performance of the proposed detail in terms of ductility, low degradation
effects and increased energy dissipation capabilities. Complementary small scale slab panel
tests are also used to further optimise the composite behaviour of the proposed detail. Additionally,
a closed form solution based on plastic limit analysis which can serve as a basis for
a simplified design approach is proposed. Finally, the main findings from the experimental
and analytical investigations are highlighted, and recommendations for future research are
outlined
Landau mapping and Fermi liquid parameters of the 2D t-J model
We study the momentum distribution function n(k) in the 2D t-J model on small
clusters by exact diagonalization. We show that n(k) can be decomposed
systematically into two components with Bosonic and Fermionic doping
dependence. The Bosonic component originates from the incoherent motion of
holes and has no significance for the low energy physics. For the Fermionic
component we exlicitely perform the one-to-one Landau mapping between the low
lying eigenstates of the t-J model clusters and those of an equivalent system
of spin-1/2 quasiparticles. This mapping allows to extract the quasiparticle
dispersion, statistics, and Landau parameters. The results show conclusively
that the 2D t-J model for small doping is a Fermi liquid with a `small' Fermi
surface and a moderately strong attractive interaction between the
quasiparticles.Comment: Revtex file, 5 pages with 5 embedded eps-files, hardcopies of figures
(or the entire manuscript) can be obtained by e-mail request to:
[email protected]
Mott transition and ferrimagnetism in the Hubbard model on the anisotropic kagom\'e lattice
Mott transition and ferrimagnetism are studied in the Hubbard model on the
anisotropic kagom\'e lattice using the variational cluster approximation and
the phase diagram at zero temperature and half-filling is analyzed. The
ferrimagnetic phase rapidly grows as the geometric frustration is relaxed, and
the Mott insulator phase disappears in moderately frustrated region, showing
that the ferrimagnetic fluctuations stemming from the relaxation of the
geometric frustration is enhanced by the electron correlations. In metallic
phase, heavy fermion behavior is observed and mass enhancement factor is
computed. Enhancement of effective spatial anisotropy by the electron
correlations is also confirmed in moderately frustrated region, and its effect
on heavy fermion behavior is examined.Comment: 5 pages, 6 figure
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