1,607 research outputs found
Transplanckian collisions at future accelerators
Scattering at transplanckian energies offers model independent tests of TeV
scale gravity. Black-hole production is one spectacular signal, though a full
calculation of the cross section is not yet available. Another signal is given
by gravitational elastic scattering, which is maybe less spectacular but which
can be nicely computed in the forward region using the eikonal approximation.
In this talk I discuss the distinctive signatures of eikonalized scattering at
future accelerators.Comment: 11 pages, 2 figures; talk given at the XXXVIIth Rencontres de
Moriond, Electroweak Interactions and Unified Theories, Les Arcs, March 9-16,
200
Cargese Lectures on Extra Dimensions
I give a pedagogical introduction to the concepts and the tools that are
necessary to study particle physics models in higher dimensions. I then give a
more detailed presentation of warped compactifications and discuss their
possible relevance to the hierarchy problem.Comment: 56 pages, 11 figures, lectures given at Cargese School "Particle
Physics and Cosmology: the Interface'', August 200
Physics Beyond the Standard Model
I review recent theoretical work on electroweak symmetry breaking.Comment: 23 pages, 3 figures, talk at EPS International Europhysics Conference
on High Energy Physics (HEP-EPS 2005), Lisbon, Portugal, 21-27 Jul 200
A Note on Bounds of Scalar Operators in Perturbative SCFTs
Bounds on anomalous dimensions of scalar operators in 4d superconformal field
theory are explored through perturbative viewpoint. Following the recent work
of Green and Shih, in which a conjecture involved this issue is verified at the
NLO, we consider the NNLO corrections to the bounds, which are important in
some situations and can be divided into two cases where
or effects dominate respectively.
In the former case, we find that the conjecture is maintained at NNLO, while in
the later case, the statement still holds due to the null corrections arising
from .Comment: 17 pages, no figure; v2 typos fixed; v3: revised version with more
typos correcte
Comments on the Holographic Picture of the Randall-Sundrum Model
We discuss some issues about the holographic interpretation of the compact
Randall-Sundrum model, which is conjectured to be dual to a 4d field theory
with non-linearly realized conformal symmetry. We make several checks of this
conjecture. In particular, we show that the radion couples conformally to a
background 4d metric. We also discuss the interpretation of the Goldberger-Wise
mechanism for stabilizing the radion. We consider situations where the
electroweak breaking stabilizes the radion and we discuss the issue of natural
conservation of flavor quantum numbers.Comment: misprints corrected, references adde
Soft Supersymmetry Breaking in Deformed Moduli Spaces, Conformal Theories, and N = 2 Yang-Mills Theory
We give a self-contained discussion of recent progress in computing the
non-perturbative effects of small non-holomorphic soft supersymmetry breaking,
including a simple new derivation of these results based on an anomaly-free
gauged U(1)_R background. We apply these results to N = 1 theories with
deformed moduli spaces and conformal fixed points. In an SU(2) theory with a
deformed moduli space, we completely determine the vacuum expectation values
and induced soft masses. We then consider the most general soft breaking of
supersymmetry in N = 2 SU(2) super-Yang-Mills theory. An N = 2 superfield
spurion analysis is used to give an elementary derivation of the relation
between the modulus and the prepotential in the effective theory. This analysis
also allows us to determine the non-perturbative effects of all soft terms
except a non-holomorphic scalar mass, away from the monopole points. We then
use an N = 1 spurion analysis to determine the effects of the most general soft
breaking, and also analyze the monopole points. We show that naive dimensional
analysis works perfectly. Also, a soft mass for the scalar in this theory
forces the theory into a free Coulomb phase.Comment: 37 pages, LaTeX2e, 4 eps figure
R-Parity Violation and Unification
The reported anomaly in deep-inelastic scattering at HERA has revived
interest in the phenomenology of R-parity violation. From the theoretical point
of view, the existence of R-violating interactions poses two considerable
problems. The first one concerns the flavour structure of the interactions and
the origin of an appropriate suppression of flavour-changing neutral-current
processes and lepton-family transitions. The second one concerns the way of
embedding R-violating interactions in a grand unified theory (GUT) without
introducing unacceptable nucleon decay rates. We show that the second problem
can be solved by a mechanism which is purely group theoretical and does not
rely on details of the flavour theory. We construct explicit GUT models in
which our mechanism can be realized.Comment: Flipped SU(5) example modified. Conclusions unchange
CP Violation Beyond the Standard Model
We review CP violation in various extensions of the electroweak sector of the
Standard Model. A particular emphasis is put on supersymmetric models. We
describe the two CP problems of supersymmetry, concerning and
. We critically review the various mechanisms that have been
suggested to solve these problems: exact universality, approximate CP symmetry,
alignment, approximate universality and heavy squarks. We explain how future
measurements of CP violation will test these mechanisms. We describe extensions
of the quark sector and their implications on CP asymmetries in neutral B
decays, on the decay and on . We
discuss CP violation in charged scalar exchange in models with natural flavor
conservation and explain how transverse lepton polarization in meson decays can
probe such models. CP violation in neutral scalar exchange arises in models of
horizontal symmetries and may be manifest in heavy quark (b and t) physics. We
describe the implications of Left-Right Symmetric models on ,
, and CP asymmetries in B decays. Finally, we
briefly discuss the potential of future measurements of CP violation to
discover New Physics.Comment: 50 pages, harvmac, 1 figure. To appear in the Review Volume "Heavy
Flavours II", eds. A.J. Buras and M. Lindner, Advanced Series on Directions
in High Energy Physics, World Scientific Publishing Co., Singapor
Bounds in 4D Conformal Field Theories with Global Symmetry
We explore the constraining power of OPE associativity in 4D Conformal Field
Theory with a continuous global symmetry group. We give a general analysis of
crossing symmetry constraints in the 4-point function ,
where Phi is a primary scalar operator in a given representation R. These
constraints take the form of 'vectorial sum rules' for conformal blocks of
operators whose representations appear in R x R and R x Rbar. The coefficients
in these sum rules are related to the Fierz transformation matrices for the R x
R x Rbar x Rbar invariant tensors. We show that the number of equations is
always equal to the number of symmetry channels to be constrained. We also
analyze in detail two cases - the fundamental of SO(N) and the fundamental of
SU(N). We derive the vectorial sum rules explicitly, and use them to study the
dimension of the lowest singlet scalar in the Phi x Phi* OPE. We prove the
existence of an upper bound on the dimension of this scalar. The bound depends
on the conformal dimension of Phi and approaches 2 in the limit dim(Phi)-->1.
For several small groups, we compute the behavior of the bound at dim(Phi)>1.
We discuss implications of our bound for the Conformal Technicolor scenario of
electroweak symmetry breaking.Comment: 30 page
- …