14,996 research outputs found
Electric Dipole Moments in Two-Higgs-Doublet Models
Electric dipole moments are extremely sensitive probes for additional sources
of CP violation in new physics models. Specifically, they have been argued in
the past to exclude new CP-violating phases in two-Higgs-doublet models. Since
recently models including such phases have been discussed widely, we revisit
the available constraints in the presence of mechanisms which are typically
invoked to evade flavour-changing neutral currents. To that aim, we start by
assessing the necessary calculations on the hadronic, nuclear and
atomic/molecular level, deriving expressions with conservative error estimates.
Their phenomenological analysis in the context of two-Higgs-doublet models
yields strong constraints, in some cases weakened by a cancellation mechanism
among contributions from neutral scalars. While the corresponding parameter
combinations do not yet have to be unnaturally small, the constraints are
likely to preclude large effects in other CP-violating observables.
Nevertheless, the generically expected contributions to electric dipole moments
in this class of models lie within the projected sensitivity of the
next-generation experiments.Comment: 23+8 pages, 6 figures. v2: added new global analysis of the electron
EDM, including the recent ThO result, and additional references. Version
accepted for publication in JHE
Solving Hard Computational Problems Efficiently: Asymptotic Parametric Complexity 3-Coloring Algorithm
Many practical problems in almost all scientific and technological
disciplines have been classified as computationally hard (NP-hard or even
NP-complete). In life sciences, combinatorial optimization problems frequently
arise in molecular biology, e.g., genome sequencing; global alignment of
multiple genomes; identifying siblings or discovery of dysregulated pathways.In
almost all of these problems, there is the need for proving a hypothesis about
certain property of an object that can be present only when it adopts some
particular admissible structure (an NP-certificate) or be absent (no admissible
structure), however, none of the standard approaches can discard the hypothesis
when no solution can be found, since none can provide a proof that there is no
admissible structure. This article presents an algorithm that introduces a
novel type of solution method to "efficiently" solve the graph 3-coloring
problem; an NP-complete problem. The proposed method provides certificates
(proofs) in both cases: present or absent, so it is possible to accept or
reject the hypothesis on the basis of a rigorous proof. It provides exact
solutions and is polynomial-time (i.e., efficient) however parametric. The only
requirement is sufficient computational power, which is controlled by the
parameter . Nevertheless, here it is proved that the
probability of requiring a value of to obtain a solution for a
random graph decreases exponentially: , making
tractable almost all problem instances. Thorough experimental analyses were
performed. The algorithm was tested on random graphs, planar graphs and
4-regular planar graphs. The obtained experimental results are in accordance
with the theoretical expected results.Comment: Working pape
On Resumming Inflationary Perturbations beyond One-loop
It is well known that the correlation functions of a scalar field in a
quasi-de Sitter space exhibit at the loop level cumulative infra-red effects
proportional to the total number of e-foldings of inflation. Using the in-in
formalism, we explore the behavior of these infra-red effects in the large N
limit of an O(N) invariant scalar field theory with quartic self-interactions.
By resumming all higher-order loop diagrams non-perturbatively, we show that
the connected four-point correlation function, which is a signal of
non-Gaussianity, is non-perturbatively enhanced with respect to its tree-level
value.Comment: 17 pages, v2: minor corrections, to appear in jca
Intrinsic palindromic numbers
We introduce a notion of palindromicity of a natural number which is
independent of the base. We study the existence and density of palindromic and
multiple palindromic numbers, and we raise several related questions.Comment: 6 pages, Latex2
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