5,777 research outputs found
Spontaneous mass generation and the small dimensions of the Standard Model gauge groups U(1), SU(2) and SU(3)
The gauge symmetry of the Standard Model is SU(3)_c x SU(2)_L x U(1)_Y for
unknown reasons. One aspect that can be addressed is the low dimensionality of
all its subgroups. Why not much larger groups like SU(7), or for that matter,
SP(38) or E7? We observe that fermions charged under large groups acquire much
bigger dynamical masses, all things being equal at a high e.g. GUT scale, than
ordinary quarks. Should such multicharged fermions exist, they are too heavy to
be observed today and have either decayed early on (if they couple to the rest
of the Standard Model) or become reliquial dark matter (if they don't). The
result follows from strong antiscreening of the running coupling for those
larger groups (with an appropriately small number of flavors) together with
scaling properties of the Dyson-Schwinger equation for the fermion mass.Comment: 15 pages, 17 plots. This version incorporates community as well as
referee comments. Accepted for publication in Nuclear Physics
Shannon entropy and particle decays
We deploy Shannon's information entropy to the distribution of branching
fractions in a particle decay. This serves to quantify how important a given
new reported decay channel is, from the point of view of the information that
it adds to the already known ones. Because the entropy is additive, one can
subdivide the set of channels and discuss, for example, how much information
the discovery of a new decay branching would add; or subdivide the decay
distribution down to the level of individual quantum states (which can be
quickly counted by the phase space). We illustrate the concept with some
examples of experimentally known particle decay distributions.Comment: 12 pages, 18 plots; to appear in Nuclear Physics
Effect of Sunflower and Marine Oils on Ruminal Microbiota, In vitro Fermentation and Digesta Fatty Acid Profile
Funding This work has been funded by Consejería de Educación, Junta de Castilla y León (research project LE007A07). Acknowledgments We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). Support received from CICYT project AGL2005-04760-C02-02 is gratefully acknowledged.Peer reviewedPublisher PD
Evolvability meets biogeography: evolutionary potential decreases at high and low environmental favourability
This is the author accepted manuscript. The final version is available from the Royal Society via the DOI in this record.Understanding and forecasting the effects of environmental change on wild populations requires knowledge on a critical question: Do populations have the ability to evolve in response to that change? However, our knowledge on how evolution works in wild conditions under different environmental circumstances is extremely limited. We investigated how environmental variation influences the evolutionary potential of phenotypic traits. We used published data to collect or calculate 135 estimates of evolvability of morphological traits of European wild bird populations. We characterised the environmental favourability of each population throughout the species’ breeding distribution. Our results suggest that the evolutionary potential of morphological traits decreases as environmental favourability becomes high or low. Strong environmental selection pressures and high intra-specific competition may reduce species’ evolutionary potential in low and high favourability areas, respectively. This suggests that species may be least able to adapt to new climate conditions at their range margins and at the centre. Our results underscore the need to consider the evolutionary potential of populations when studying the drivers of species distributions, particularly when predicting the effects of environmental change. We discuss the utility of integrating evolutionary dynamics into a biogeographical perspective to understand how environmental variation shapes evolutionary patterns. This approach would also produce more reliable predictions about the effect of environmental change on population persistence and therefore on biodiversity.We acknowledge funding from the Spanish Ministerio de Economía y Competitividad (grants CGL2012-34685, CGL2015-70639-P, and CGL2016-76173-P) and thanks to the ERA-Net BiodivERsA, with the national funder FCT (Project: BIODIVERSA/0003/2011). AE has a contract funded by the project 1098/2014 (Organismo Autónomo Parques Nacionales, Spain)
- …