305 research outputs found

### Light Quark Masses and Mixing Angles

I review the present state of our knowledge about the masses and weak mixing
elements of the u, d, s quarks. This is the written version of lectures given
in the 1993 Theoretical Advanced Study Institute (TASI).Comment: UMHEP-402, Latex file, 27 page

### New insights concerning dimension-eight effects in weak decays

Most past work on weak nonleptonic decays has mixed dimensional
regularization in the weak operator product expansion with some form of a
cutoff regularization in the evaluation of the matrix elements. Even with the
usual technique of matching the two schemes, this combination misses physics at
short distance which can be described by dimension eight (and higher dimension)
operators. I describe some recent work with V. Cirigliano and E. Golowich which
clarifies these effects and provides a numerical estimate suggesting that they
are important.Comment: 3 pages, talk presented at the Division of Particles and Fields
Meeting, DPF 2000, Columbus, Ohio, Aug. 200

### Sigma exchange in the nuclear force and effective field theory

In the phenomenological description of the nuclear interaction a crucial role
is traditionally played by the exchange of a scalar I=0 meson, the sigma, of
mass 500-600 MeV, which however is not seen clearly in the particle spectrum
and which has a very ambiguous status in QCD. I show that a remarkably simple
and reasonably controlled combination of ingredients can reproduce the features
of this part of the nuclear force. The use of chiral perturbation theory
calculations for two pion exchange supplemented by the Omnes function for pion
rescattering suffices to reproduce the magnitude and shape of the exchange of a
supposed $\sigma$ particle, even though no such particle is present in this
calculation. I also show how these ingredients can describe the contact
interaction that enters more modern descriptions of the internucleon
interaction.Comment: 10 pages, 5 figures, Normalization in Fig 3b correcte

### Dynamics of M-theory vacua

At very early times, the universe was not in a vacuum state. Under the
assumtion that the deviation from equillibrium was large, in particular that it
is higher than the scale of inflation, we analyse the conditions for local
transitions between states that are related to different vacua. All pathways
lead to an attractor solution of a description of the universe by eternal
inflation with domains that have different low energy parameters. The generic
case favors transitions between states that have significantly different
parameters rather than jumps between nearby states in parameter space. I argue
that the strong CP problem presents a potential difficulty for this picture,
more difficult than the hierarchy problem or the cosmological constant problem.
Finally, I describe how the spectrum of quark masses may be a probe of the
early dynamics of vacuum states. As an example, by specializing to the case of
intersecting braneworld models, I show that the observed mass spectrum, which
is approximately scale invariant, corresponds to a flat distribution in the
intersection area of the branes, with a maximum area A_max ~ 100 alpha'.Comment: 30 pages, 3 figure

### When Effective Field Theories Fail

In this talk, I describe and defend four non-standard claims about four
effective field theories, and try to extract some lessons about the limits of
effective field theory. The four theses (and a capsule diagnosis given in
parentheses) are: 1) Kaon loops are not a reliable part of chiral perturbation
theory (dimensional regularization does not know about the chiral scale), 2)
Regge physics is inappropriately missing from SCET (an infinite set of scales
are needed) 3) There is likely a barrier in the use of EFT in general
relativity in the extreme infrared (curvature effects build up) and 4) Gauge
non-invariant operators should be included in describing physics beyond the
Standard Model (as they could probe the idea of emergent gauge symmetry and
falsify string theory).Comment: Opening talk at the International Workshop on Effective Field
Theories, Valencia, 2-6 February 2009. 15 pages, 6 figure

### The effective field theory treatment of quantum gravity

This is a pedagogical introduction to the treatment of quantum general
relativity as an effective field theory. It starts with an overview of the
methods of effective field theory and includes an explicit example. Quantum
general relativity matches this framework and I discuss gravitational examples
as well as the limits of the effective field theory. I also discuss the
insights from effective field theory on the gravitational effects on running
couplings in the perturbative regime.Comment: Presented at the Sixth International School on Field Theory and
Gravitation, Petropolis, Brazil, April 2012, to be published in the
proceedings. 22 pages, 3 figure

### Introduction to the Effective Field Theory Description of Gravity

This is a pedagogical introduction to the treatment of general relativity as
a quantum effective field theory. Gravity fits nicely into the effective field
theory description and forms a good quantum theory at ordinary energies.Comment: 26 pages, Latex, no figures, Lectures presented at the Advanced
School on Effective Field Theories (Almunecar, Spain, June 1995), to be
published in the proceeding

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