950 research outputs found
Leptogenesis without CP Violation at Low Energies
In this letter we give a class of examples where the decays of the heavy
Majorana neutrinos may violate CP even if there is no CP violation at low
energies, i.e., leptogenesis can take place without Majorana or Dirac type CP
phases at low energies.Comment: 7 pages, no figures. One comment and references added. Version proof
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A Simple Method to detect spontaneous CP Violation in multi-Higgs models
For models with several Higgs doublets we present an alternative method to
the one proposed by Branco, Gerard and Grimus, in 1984, to check whether or not
CP is spontaneously violated in the Higgs potential. The previous method is
powerful and rigorous. It requires the identification of a matrix
corresponding to a symmetry of the Lagrangian and verifying a simple relation
involving the vacuum expectation values. The nonexistence of such a matrix
signals spontaneous CP violation. However, as the number of Higgs doublets
increases, finding such a matrix may not be straightforward and it may turn
out to be easier to analyse the potential by going to the so-called Higgs
basis. The transformation to the Higgs basis is straightforward once the vacuum
expectation values are known. The method proposed in this work is also powerful
and rigorous and can be particularly useful to analyse models with more than
two Higgs doublets and with continuous symmetries.Comment: 9 pages, no figures. v2: minor changes, matching JHEP versio
Impact of Inter-Country Distances on International Tourism
Tourism is a worldwide practice with international tourism revenues
increasing from US\$495 billion in 2000 to US\$1340 billion in 2017. Its
relevance to the economy of many countries is obvious. Even though the World
Airline Network (WAN) is global and has a peculiar construction, the
International Tourism Network (ITN) is very similar to a random network and
barely global in its reach. To understand the impact of global distances on
local flows, we map the flow of tourists around the world onto a complex
network and study its topological and dynamical balance. We find that although
the WAN serves as infrastructural support for the ITN, the flow of tourism does
not correlate strongly with the extent of flight connections worldwide.
Instead, unidirectional flows appear locally forming communities that shed
light on global travelling behaviour inasmuch as there is only a 15%
probability of finding bidirectional tourism between a pair of countries. We
conjecture that this is a consequence of one-way cyclic tourism by analyzing
the triangles that are formed by the network of flows in the ITN. Finally, we
find that most tourists travel to neighbouring countries and mainly cover
larger distances when there is a direct flight, irrespective of the time it
takes
Leptonic CP Violation and Leptogenesis
We review some recent results on the connection between CP violation at low
energies and Leptogenesis in the framework of specific flavour structures for
the fundamental leptonic mass matrices with zero textures.Comment: Invited talk, to appear in the proceedings of 6th International
Heidelberg Conference on Dark Matter in Astro and Particle Physics, Sydney,
Australia, 24-28 Sep 2007. Reference number, cited in the last paragraph,
correcte
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