64 research outputs found
The Renormalization Structure and Quantum Equivalence of 2D Dilaton Gravities
The one-loop effective action corresponding the general model of dilaton
gravity given by the Lagrangian , where , and are arbitrary
functions of the dilaton field, is found. The question of the quantum
equivalence of classically equivalent dilaton gravities is studied. By specific
calculation of explicit examples it is shown that classically equivalent
quantum gravities are also perturbatively equivalent at the quantum level, but
only on-shell. The renormalization group equations for the generalized
effective couplings , and are written. An
analysis of the equations shows, in particular, that the
Callan-Giddings-Harvey-Strominger model is not a fixed point of these
equations.Comment: 25 pages, LaTeX file, April 2
2D Dilaton-Maxwell Gravity as a Fixed Point of the Renormalization Group
A general model of dialton-Maxwell gravity in two dimensions is investigated.
The corresponding one-loop effective action and the generalized
-functions are obtained. A set of models that are fixed points of the
renormalization group equations are presented.Comment: 7 pages, LaTeX file, UB-ECM-PF 92/Mar1
One Loop Counterterms in 2D Dilaton-Maxwell Quantum Gravity
The renormalization structure of two-dimensional quantum gravity is
investigated, in a covariant gauge. One-loop divergences of the effective
action are calculated. All the surface divergent terms are taken into account,
thus completing previous one-loop calculations of the theory. It is shown that
the on-shell effective action contains only surface divergences. The off-shell
renormalizability of the theory is discussed and classes of renormalizable
dilaton and Maxwell potentials are found.Comment: 9 pages, LaTeX file, HUPD-92-1
One-Loop Renormalization of Higher-Derivative 2D Dilaton Gravity
A theory of higher-derivative 2D dilaton gravity which has its roots in the
massive higher-spin mode dynamics of string theory is suggested. The
divergences of the effective action to one-loop are calculated, both in the
covariant and in the conformal gauge. Some technical problems which appear in
the calculations are discussed. An interpretation of the theory as a particular
D=2 higher-derivative -model is given. For a specific case of
higher-derivative 2D dilaton gravity, which is one loop multiplicatively
renormalizable, static configurations corresponding to black holes are shown to
exist.Comment: 12 pages, LaTeX fil
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Convenient Versus Unique Effective Action Formalism in 2D Dilaton-Maxwell Quantum Gravity
The structure of one-loop divergences of two-dimensional dilaton-Maxwell
quantum gravity is investigated in two formalisms: one using a convenient
effective action and the other a unique effective action. The one-loop
divergences (including surface divergences) of the convenient effective action
are calculated in three different covariant gauges: (i) De Witt, (ii)
-degenerate De Witt, and (iii) simplest covariant. The on-shell
effective action is given by surface divergences only (finiteness of the
-matrix), which yet depend upon the gauge condition choice.
Off-shell renormalizability is discussed and classes of renormalizable
dilaton and Maxwell potentials are found which coincide in the cases of
convenient and unique effective actions. A detailed comparison of both
situations, i.e. convenient vs. unique effective action, is given. As an
extension of the procedure, the one-loop effective action in two-dimensional
dilaton-Yang-Mills gravity is calculated.Comment: 25 pages, LaTeX file, HUPD-93-0
Covariant Effective Action and One-Loop Renormalization of 2D Dilaton Gravity with Fermionic Matter
Two dimensional dilaton gravity interacting with a four-fermion model and
scalars is investigated, all the coefficients of the Lagrangian being arbitrary
functions of the dilaton field. The one-loop covariant effective action for 2D
dilaton gravity with Majorana spinors (including the four-fermion interaction)
is obtained, and the technical problems which appear in an attempt at
generalizing such calculations to the case of the most general four-fermion
model described by Dirac fermions are discussed. A solution to these problems
is found, based on its reduction to the Majorana spinor case.
The general covariant effective action for 2D dilaton gravity with the
four-fermion model described by Dirac spinors is given. The one-loop
renormalization of dilaton gravity with Majorana spinors is carried out and the
specific conditions for multiplicative renormalizability are found. A
comparison with the same theory but with a classical gravitational field is
done.Comment: LaTeX, 25 pages, july 2
How are "teaching the teachers" courses in evidence based medicine evaluated? A systematic review
Background
Teaching of evidence-based medicine (EBM) has become widespread in medical education. Teaching the teachers (TTT) courses address the increased teaching demand and the need to improve effectiveness of EBM teaching. We conducted a systematic review of assessment tools for EBM TTT courses. To summarise and appraise existing assessment methods for teaching the teachers courses in EBM by a systematic review.
Methods
We searched PubMed, BioMed, EmBase, Cochrane and Eric databases without language restrictions and included articles that assessed its participants. Study selection and data extraction were conducted independently by two reviewers.
Results
Of 1230 potentially relevant studies, five papers met the selection criteria. There were no specific assessment tools for evaluating effectiveness of EBM TTT courses. Some of the material available might be useful in initiating the development of such an assessment tool.
Conclusion
There is a need for the development of educationally sound assessment tools for teaching the teachers courses in EBM, without which it would be impossible to ascertain if such courses have the desired effect
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