43 research outputs found
Only Three
It is shown that it is possible to account for all experimental indications
for neutrino oscillations with just three flavours. In particular we suggest
that the atmospheric neutrino anomaly and the LSND result can be explained by
the same mass difference and mixing. Possible implications and future tests of
the resulting mass and mixing pattern are given.Comment: 10 pages, 2 Postscript figures (eps
Neutrino mixing and masses from long baseline and atmospheric oscillation experiments
We argue that regardless of the outcome of future Long Baseline experiments,
additional information will be needed to unambiguously decide among the
different scenarios of neutrino mixing. We use, for this purpose, a simple test
of underground data: an asymmetry between downward and upward going events.
Such an asymmetry, in which matter effects can be crucial, tests electron and
muon neutrino data separately and can be compared with the theoretical
prediction without relying on any simulation program.Comment: 9 pages, 2 figures (eps
Sweeping the Space of Admissible Quark Mass Matrices
We propose a new and efficient method of reconstructing quark mass matrices
from their eigenvalues and a complete set of mixing observables. By a
combination of the principle of NNI (nearest neighbour interaction) bases which
are known to cover the general case, and of the polar decomposition theorem
that allows to convert arbitrary nonsingular matrices to triangular form, we
achieve a parameterization where the remaining freedom is reduced to one
complex parameter. While this parameter runs through the domain bounded by a
circle with radius R determined by the up-quark masses around the origin in the
complex plane one sweeps the space of all mass matrices compatible with the
given set of data.Comment: 18 page
Renormalization in Quantum Field Theory: An Improved Rigorous Method
The perturbative construction of the S-matrix in the causal spacetime
approach of Epstein and Glaser may be interpreted as a method of regularization
for divergent Feynman diagrams. The results of any method of regularization
must be equivalent to those obtained from the Epstein-Glaser (EG) construction,
within the freedom left by the latter. In particular, the conceptually
well-defined approach of Bogoliubov, Parasuk, Hepp, and Zimmermann (BPHZ),
though conceptually different from EG, meets this requirement. Based on this
equivalence we propose a modified BPHZ procedure which provides a significant
simplification of the techniques of perturbation theory, and which applies
equally well to standard quantum field theory and to chiral theories. We
illustrate the proposed method by a number of examples of various orders in
perturbation theory. At the level of multi-loop diagrams we find that
subdiagrams as classified by Zimmermann's forest formula in BPHZ may be
restricted to subdiagrams in the sense of Epstein-Glaser, thus entailing an
important reduction of actual computations. Furthermore, the relationship of
our approach to the method of dimensional regularization is particularly
transparent, without having to invoke analytic continuation to unphysical
spacetime dimension, and sheds new light on certain parameters within
dimensional regularization.Comment: 19 pages, 3 figure
Is Strong SASI Activity the Key to Successful Neutrino-Driven Supernova Explosions?
Following a simulation approach of recent publications we explore the
viability of the neutrino-heating explosion mechanism in dependence on the
spatial dimension. Our results disagree with previous findings. While we also
observe that two-dimensional (2D) models explode for lower driving neutrino
luminosity than spherically symmetric (1D) models, we do not find that
explosions in 3D occur easier and earlier than in 2D. Moreover, we find that
the average entropy of matter in the gain layer hardly depends on the dimension
and thus is no good diagnostic quantity for the readiness to explode. Instead,
mass, integrated entropy, total neutrino-heating rate, and nonradial kinetic
energy in the gain layer are higher when models are closer to explosion.
Coherent, large-scale mass motions as typically associated with the standing
accretion-shock instability (SASI) are observed to be supportive for explosions
because they drive strong shock expansion and thus enlarge the gain layer.
While 2D models with better angular resolution explode clearly more easily, the
opposite trend is seen in 3D. We interpret this as a consequence of the
turbulent energy cascade, which transports energy from small to large spatial
scales in 2D, thus fostering SASI activity. In contrast, the energy flow in 3D
is in the opposite direction, feeding fragmentation and vortex motions on
smaller scales and thus making the 3D evolution with finer grid resolution more
similar to 1D. More favorable conditions for explosions in 3D may therefore be
tightly linked to efficient growth of low-order SASI modes including
nonaxisymmetric ones.Comment: 25 pages, 20 figures, 33 eps files; significant extension due to
referee comments and more simulations; version accepted by Ap
Mechanics: From Newton’s Laws to Deterministic Chaos /
This book covers all topics in mechanics from elementary Newtonian mechanics, the principles of canonical mechanics and rigid body mechanics to relativistic mechanics and nonlinear dynamics. It was among the first textbooks to include dynamical systems and deterministic chaos in due detail. As compared to the previous editions the present fifth edition is updated and revised with more explanations, additional examples and sections on Noether's theorem. Symmetries and invariance principles, the basic geometric aspects of mechanics as well as elements of continuum mechanics also play an important role. The book will enable the reader to develop general principles from which equations of motion follow, to understand the importance of canonical mechanics and of symmetries as a basis for quantum mechanics, and to get practice in using general theoretical concepts and tools that are essential for all branches of physics. The book contains more than 120 problems with complete solutions, as well as some practical examples which make moderate use of personal computers. This will be appreciated in particular by students using this textbook to accompany lectures on mechanics. The book ends with some historical notes on scientists who made important contributions to the development of mechanics
Mechanics: From Newton’s Laws to Deterministic Chaos
This updated and revised fourth edition covers all topics in mechanics from elementary Newtonian mechanics, canonical and rigid body mechanics to relativistic mechanics and nonlinear dynamics. In particular, symmetries and invariance principles, geometrical structures and continuum mechanics play an important role. This book will enable the reader to develop general principles from which equations of motions may be derived, to understand the importance of symmetries as a basis for quantum mechanics and to get practice in using theoretical tools and concepts that are essential for all branches of physics. The book contains numerous problems with complete solutions, and some practical examples.This will be appreciated in particular by students using the text to accompnay lectures on mechanics. The book ends with some historical remarks on important pioneers in mechanics
Quantum physics
This book presents a comprehensive introduction to quantum physics. Part One covers the basic principles and prime applications of quantum mechanics, from the uncertainty relations to many-body systems. Part Two introduces to relativistic quantum field theory, and ranges from symmetries in quantum physics to electroweak interactions. Numerous worked-out examples as well as exercises with solutions, or hints, make the book useful as accompanying text for courses as well as for independent individual study. For both parts the necessary mathematical framework is treated in adequate form and detail. The book ends with selected biographical notes on pioneers of quantum mechanics and quantum field theory