930 research outputs found
Introduction to Chiral Perturbation Theory
A brief introduction to chiral perturbation theory, the effective field
theory of quantum chromodynamics at low energies, is given.Comment: 26 pages, 11 figures. Lectures given at the summer school ISSSMB 2006
in Akyaka, Turkey, September 200
Baryogenesis from a right-handed neutrino condensate
We show that the baryon asymmetry of the Universe can be generated by a
strongly coupled right handed neutrino condensate which also drives inflation.
The resulting model has only a small number of parameters, which completely
determine not only the baryon asymmetry of the Universe and the mass of the
right handed neutrino but also the inflationary phase. This feature allows us
to make predictions that will be tested by current and planned experiments. As
compared to the usual approach our dynamical framework is both economical and
predictive.Comment: 13 pages, 3 figures. Typos corrected and several points clarified.
Results unchanged. New references adde
Prebiotic Homochirality as a Critical Phenomenon
The development of prebiotic homochirality on early-Earth or another
planetary platform may be viewed as a critical phenomenon. It is shown, in the
context of spatio-temporal polymerization reaction networks, that environmental
effects -- be them temperature surges or other external disruptions -- may
destroy any net chirality previously produced. In order to understand the
emergence of prebiotic homochirality it is important to model the coupling of
polymerization reaction networks to different planetary environments.Comment: 6 Pages, 1 Figure, In Press: Origins of Life and Evolution of
Biosphere
On the dynamical generation of the Maxwell term and scale invariance
Gauge theories with no Maxwell term are investigated in various setups. The
dynamical generation of the Maxwell term is correlated to the scale invariance
properties of the system. This is discussed mainly in the cases where the gauge
coupling carries dimensions. The term is generated when the theory contains a
scale explicitly, when it is asymptotically free and in particular also when
the scale invariance is spontaneously broken. The terms are not generated when
the scale invariance is maintained. Examples studied include the large
limit of the model in dimensions, a 3D gauged
vector model and its supersymmetric extension. In the latter case the
generation of the Maxwell term at a fixed point is explored. The phase
structure of the case is investigated in the presence of a Chern-Simons
term as well. In the supersymmetric model the emergence of the Maxwell
term is accompanied by the dynamical generation of the Chern-Simons term and
its multiplet and dynamical breaking of the parity symmetry. In some of the
phases long range forces emerge which may result in logarithmic confinement.
These include a dilaton exchange which plays a role also in the case when the
theory has no gauge symmetry. Gauged Lagrangian realizations of the 2D coset
models do not lead to emergent Maxwell terms. We discuss a case where the gauge
symmetry is anomalous.Comment: 38 pages, 4 figures; v2 slightly improved, typos fixed, references
added, published versio
QCD axion and quintessential axion
The axion solution of the strong CP problem is reviewed together with the
other strong CP solutions. We also point out the quintessential
axion(quintaxion) whose potential can be extremely flat due to the tiny ratio
of the hidden sector quark mass and the intermediate hidden sector scale. The
quintaxion candidates are supposed to be the string theory axions, the model
independent or the model dependent axions.Comment: 15 pages. Talk presented at Castle Ringberg, June 9-14, 200
Revisiting special relativity: A natural algebraic alternative to Minkowski spacetime
Minkowski famously introduced the concept of a space-time continuum in 1908,
merging the three dimensions of space with an imaginary time dimension , with the unit imaginary producing the correct spacetime distance , and the results of Einstein's then recently developed theory of special
relativity, thus providing an explanation for Einstein's theory in terms of the
structure of space and time. As an alternative to a planar Minkowski space-time
of two space dimensions and one time dimension, we replace the unit imaginary , with the Clifford bivector for the plane
that also squares to minus one, but which can be included without the addition
of an extra dimension, as it is an integral part of the real Cartesian plane
with the orthonormal basis and . We find that with this model of
planar spacetime, using a two-dimensional Clifford multivector, the spacetime
metric and the Lorentz transformations follow immediately as properties of the
algebra. This also leads to momentum and energy being represented as components
of a multivector and we give a new efficient derivation of Compton's scattering
formula, and a simple formulation of Dirac's and Maxwell's equations. Based on
the mathematical structure of the multivector, we produce a semi-classical
model of massive particles, which can then be viewed as the origin of the
Minkowski spacetime structure and thus a deeper explanation for relativistic
effects. We also find a new perspective on the nature of time, which is now
given a precise mathematical definition as the bivector of the plane.Comment: 29 pages, 2 figure
d=3 Bosonic Vector Models Coupled to Chern-Simons Gauge Theories
We study three dimensional O(N)_k and U(N)_k Chern-Simons theories coupled to
a scalar field in the fundamental representation, in the large N limit. For
infinite k this is just the singlet sector of the O(N) (U(N)) vector model,
which is conjectured to be dual to Vasiliev's higher spin gravity theory on
AdS_4. For large k and N we obtain a parity-breaking deformation of this
theory, controlled by the 't Hooft coupling lambda = 4 \pi N / k. For infinite
N we argue (and show explicitly at two-loop order) that the theories with
finite lambda are conformally invariant, and also have an exactly marginal
(\phi^2)^3 deformation.
For large but finite N and small 't Hooft coupling lambda, we show that there
is still a line of fixed points parameterized by the 't Hooft coupling lambda.
We show that, at infinite N, the interacting non-parity-invariant theory with
finite lambda has the same spectrum of primary operators as the free theory,
consisting of an infinite tower of conserved higher-spin currents and a scalar
operator with scaling dimension \Delta=1; however, the correlation functions of
these operators do depend on lambda. Our results suggest that there should
exist a family of higher spin gravity theories, parameterized by lambda, and
continuously connected to Vasiliev's theory. For finite N the higher spin
currents are not conserved.Comment: 34 pages, 29 figures. v2: added reference
Convergence properties of decays in chiral perturbation theory
Theoretical efforts to describe and explain the decays reach
far back in time. Even today, the convergence of the decay widths and some of
the Dalitz plot parameters seems problematic in low energy QCD. In the
framework of resummed CHPT, we explore the question of compatibility of
experimental data with a reasonable convergence of a carefully defined chiral
series, where NNLO remainders are assumed to be small. By treating the
uncertainties in the higher orders statistically, we numerically generate a
large set of theoretical predictions, which are then confronted with
experimental information. In the case of the decay widths, the experimental
values can be reconstructed for a reasonable range of the free parameters and
thus no tension is observed, in spite of what some of the traditional
calculations suggest. The Dalitz plot parameters and can be described
very well too. When the parameters and are concerned, we find a
mild tension for the whole range of the free parameters, at less than 2
C.L. This can be interpreted in two ways - either some of the higher order
corrections are indeed unexpectedly large or there is a specific configuration
of the remainders, which is, however, not completely improbable. Also, the
distribution of the theoretical uncertainties is found to be significantly
non-gaussian, so the consistency cannot be simply judged by the 1 error
bars.Comment: 57 pages, 5 figure
Physics Opportunities of e+e- Linear Colliders
We describe the anticipated experimental program of an e+e- linear collider
in the energy range 500 GeV -- 1.5 TeV. We begin with a description of current
collider designs and the expected experimental environment. We then discuss
precision studies of the W boson and top quark. Finally, we review the range of
models proposed to explain the physics of electroweak symmetry breaking and
show, for each case, the central role that the linear collider experiments will
play in elucidating this physics. (to appear in Annual Reviews of Nuclear and
Particle Science)Comment: 93 pages, latex + 23 figures; typos corrections + 1 reference adde
Goldstone Bosons in Effective Theories with Spontaneously Broken Flavour Symmetry
The Flavour Symmetry of the Standard Model (SM) gauge sector is broken by the
fermion Yukawa couplings. Promoting the Yukawa matrices to scalar spurion
fields, one can break the flavour symmetry spontaneously by giving appropriate
vacuum expectation values (VEVs) to the spurion fields, and one encounters
Goldstone modes for every broken flavour symmetry generator. In this paper, we
point out various aspects related to the possible dynamical interpretation of
the Goldstone bosons: (i) In an effective-theory framework with local flavour
symmetry, the Goldstone fields represent the longitudinal modes for massive
gauge bosons. The spectrum of the latter follows the sequence of
flavour-symmetry breaking related to the hierarchies in Yukawa couplings and
flavour mixing angles. (ii) Gauge anomalies can be consistently treated by
adding higher-dimensional operators. (iii) Leaving the U(1) factors of the
flavour symmetry group as global symmetries, the respective Goldstone modes
behave as axions which can be used to resolve the strong CP problem by a
modified Peccei-Quinn mechanism. (iv) The dynamical picture of flavour symmetry
breaking implies new sources of flavour-changing neutral currents, which arise
from integrating out heavy scalar spurion fields and heavy gauge bosons. The
coefficients of the effective operators follow the minimal-flavour violation
principle.Comment: 27 pages, abstract and introduction extended, more detailed
discussion of heavy gauge boson spectrum and auxiliary heavy fermions,
outline restructured. Matches version to be published in JHE
- …