2,736 research outputs found
Seesaw and Lepton Flavour Violation in SUSY SO(10)
That and are sensitive probes of
SUSY models with a see-saw mechanism is a well accepted fact. Here we propose a
`top-down' approach in a general SUSY SO(10) scheme. In this framework, we show
that at least one of the neutrino Yukawa couplings is as large as the top
Yukawa coupling. This leads to a strong enhancement of these leptonic flavour
changing decay rates. We examine two `extreme' cases, where the lepton mixing
angles in the neutrino Yukawa couplings are either small (CKM-like) or large
(PMNS-like). In these two cases, we quantify the sensitivity of leptonic
radiative decays to the SUSY mass spectrum. In the PMNS case, we find that the
ongoing experiments at the B-factories can completely probe the spectrum up to
gaugino masses of 500 GeV (any tan ). Even in the case of CKM-like
mixings, large regions of the parameter space will be probed in the near
future, making these two processes leading candidates for indirect SUSY
searches.Comment: 22 pages with 2 figures. Figures for \tau -> \mu \gamma decay
corrected after typo found in the program. Decay \mu -> e gamma completely
unchanged and conclusions basicaly unchange
babble: Learning Better Abstractions with E-Graphs and Anti-Unification
Library learning compresses a given corpus of programs by extracting common
structure from the corpus into reusable library functions. Prior work on
library learning suffers from two limitations that prevent it from scaling to
larger, more complex inputs. First, it explores too many candidate library
functions that are not useful for compression. Second, it is not robust to
syntactic variation in the input.
We propose library learning modulo theory (LLMT), a new library learning
algorithm that additionally takes as input an equational theory for a given
problem domain. LLMT uses e-graphs and equality saturation to compactly
represent the space of programs equivalent modulo the theory, and uses a novel
e-graph anti-unification technique to find common patterns in the corpus more
directly and efficiently.
We implemented LLMT in a tool named BABBLE. Our evaluation shows that BABBLE
achieves better compression orders of magnitude faster than the state of the
art. We also provide a qualitative evaluation showing that BABBLE learns
reusable functions on inputs previously out of reach for library learning.Comment: POPL 202
Density-Dependence as a Size-Independent Regulatory Mechanism
The growth function of populations is central in biomathematics. The main
dogma is the existence of density dependence mechanisms, which can be modelled
with distinct functional forms that depend on the size of the population. One
important class of regulatory functions is the -logistic, which
generalises the logistic equation. Using this model as a motivation, this paper
introduces a simple dynamical reformulation that generalises many growth
functions. The reformulation consists of two equations, one for population
size, and one for the growth rate. Furthermore, the model shows that although
population is density-dependent, the dynamics of the growth rate does not
depend either on population size, nor on the carrying capacity. Actually, the
growth equation is uncoupled from the population size equation, and the model
has only two parameters, a Malthusian parameter and a competition
coefficient . Distinct sign combinations of these parameters reproduce
not only the family of -logistics, but also the van Bertalanffy,
Gompertz and Potential Growth equations, among other possibilities. It is also
shown that, except for two critical points, there is a general size-scaling
relation that includes those appearing in the most important allometric
theories, including the recently proposed Metabolic Theory of Ecology. With
this model, several issues of general interest are discussed such as the growth
of animal population, extinctions, cell growth and allometry, and the effect of
environment over a population.Comment: 41 Pages, 5 figures Submitted to JT
Symbolic Implementation of Connectors in BIP
BIP is a component framework for constructing systems by superposing three
layers of modeling: Behavior, Interaction, and Priority. Behavior is
represented by labeled transition systems communicating through ports.
Interactions are sets of ports. A synchronization between components is
possible through the interactions specified by a set of connectors. When
several interactions are possible, priorities allow to restrict the
non-determinism by choosing an interaction, which is maximal according to some
given strict partial order.
The BIP component framework has been implemented in a language and a
tool-set. The execution of a BIP program is driven by a dedicated engine, which
has access to the set of connectors and priority model of the program. A key
performance issue is the computation of the set of possible interactions of the
BIP program from a given state.
Currently, the choice of the interaction to be executed involves a costly
exploration of enumerative representations for connectors. This leads to a
considerable overhead in execution times. In this paper, we propose a symbolic
implementation of the execution model of BIP, which drastically reduces this
overhead. The symbolic implementation is based on computing boolean
representation for components, connectors, and priorities with an existing BDD
package
Closed Type Families With Overlapping Equations (Extended Version)
Open, type-level functions are a recent innovation in Haskell that move Haskell towards the expressiveness of dependent types, while retaining the look and feel of a practical programming language. This paper shows how to increase expressiveness still further, by adding closed type functions whose equations may overlap, and may have non-linear patterns over an open type universe. Although practically useful and simple to implement, these features go beyond conventional dependent type theory in some respects, and have a subtle metatheory
- …