15,137 research outputs found
FCNCs in supersymmetric multi-Higgs doublet models
We conduct a general discussion of supersymmetric models with three families
in the Higgs sector. We analyse the scalar potential, and investigate the
minima conditions, deriving the mass matrices for the scalar, pseudoscalar and
charged states. Depending on the Yukawa couplings and the Higgs spectrum, the
model might allow the occurrence of potentially dangerous flavour changing
neutral currents at the tree-level. We compute model-independent contributions
for several observables, and as an example we apply this general analysis to a
specific model of quark-Higgs interactions, discussing how compatibility with
current experimental data constrains the Higgs sector.Comment: 30 pages, 9 figures. Comments and references added. Final version
published in Physical Review
Influences of thermal environment on fish growth
Indexación: Scopus.Thermoregulation in ectothermic animals is influenced by the ability to effectively respond to thermal variations. While it is known that ectotherms are affected by thermal changes, it remains unknown whether physiological and/or metabolic traits are impacted by modifications to the thermal environment. Our research provides key evidence that fish ectotherms are highly influenced by thermal variability during development, which leads to important modifications at several metabolic levels (e.g., growth trajectories, microstructural alterations, muscle injuries, and molecular mechanisms). In Atlantic salmon (Salmo salar), a wide thermal range (ΔT 6.4°C) during development (posthatch larvae to juveniles) was associated with increases in key thermal performance measures for survival and growth trajectory. Other metabolic traits were also significantly influenced, such as size, muscle cellularity, and molecular growth regulators possibly affected by adaptive processes. In contrast, a restricted thermal range (ΔT 1.4°C) was detrimental to growth, survival, and cellular microstructure as muscle growth could not keep pace with increased metabolic demands. These findings provide a possible basic explanation for the effects of thermal environment during growth. In conclusion, our results highlight the key role of thermal range amplitude on survival and on interactions with major metabolism-regulating processes that have positive adaptive effects for organisms.http://onlinelibrary.wiley.com/doi/10.1002/ece3.3239/ful
Novel sum rules for the three-point sector of QCD
For special kinematic configurations involving a single momentum scale,
certain standard relations, originating from the Slavnov-Taylor identities of
the theory, may be interpreted as ordinary differential equations for the
``kinetic term'' of the gluon propagator. The exact solutions of these
equations exhibit poles at the origin, which are incompatible with the physical
answer, known to diverge only logarithmically; their elimination hinges on the
validity of two integral conditions that we denominate ``asymmetric'' and
``symmetric'' sum rules, depending on the kinematics employed in their
derivation. The corresponding integrands contain components of the three-gluon
vertex and the ghost-gluon kernel, whose dynamics are constrained when the sum
rules are imposed. For the numerical treatment we single out the asymmetric sum
rule, given that its support stems predominantly from low and intermediate
energy regimes of the defining integral, which are physically more interesting.
Adopting a combined approach based on Schwinger-Dyson equations and lattice
simulations, we demonstrate how the sum rule clearly favors the suppression of
an effective form factor entering in the definition of its kernel. The results
of the present work offer an additional vantage point into the rich and complex
structure of the three-point sector of QCD.Comment: 34 pages, 7 figures, 1 tabl
Gluon dynamics from an ordinary differential equation
We present a novel method for computing the nonperturbative kinetic term of
the gluon propagator from an exactly solvable ordinary differential equation,
whose origin is the fundamental Slavnov-Taylor identity satisfied by the
three-gluon vertex, evaluated in a special kinematic limit. The main
ingredients comprising the solution are a well-known projection of the
three-gluon vertex, simulated on the lattice, and a particular derivative of
the ghost-gluon kernel, whose approximate form is derived from a standard
Schwinger-Dyson equation. Crucially, the physical requirement of a pole-free
answer determines completely the form of the initial condition, whose value is
calculated from a specific integral containing the same ingredients as the
solution itself. This outstanding feature fixes uniquely, at least in
principle, the form of the kinetic term, once the ingredients of the
differential equation have been accurately evaluated. Furthermore, in the case
where the gluon propagator has been independently accessed from the lattice,
this property leads to the unambiguous extraction of the momentum-dependent
effective gluon mass. The practical implementation of this method is carried
out in detail, and the required approximations and theoretical assumptions are
duly highlighted. The systematic improvement of this approach through the
detailed computation of one of its pivotal components is briefly outlined.Comment: 35 pages, 12 figures, 2 table
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Controllable direction of liquid jets generated by thermocavitation within a droplet.
A high-velocity fluid stream ejected from an orifice or nozzle is a common mechanism to produce liquid jets in inkjet printers or to produce sprays among other applications. In the present research, we show the generation of liquid jets of controllable direction produced within a sessile water droplet by thermocavitation. The jets are driven by an acoustic shock wave emitted by the collapse of a hemispherical vapor bubble at the liquid-solid/substrate interface. The generated shock wave is reflected at the liquid-air interface due to acoustic impedance mismatch generating multiple reflections inside the droplet. During each reflection, a force is exerted on the interface driving the jets. Depending on the position of the generation of the bubble within the droplet, the mechanical energy of the shock wave is focused on different regions at the liquid-air interface, ejecting cylindrical liquid jets at different angles. The ejected jet angle dependence is explained by a simple ray tracing model of the propagation of the acoustic shock wave inside the droplet
Nonperturbative Ball-Chiu construction of the three-gluon vertex
We present the detailed derivation of the longitudinal part of the
three-gluon vertex from the Slavnov-Taylor identities that it satisfies, by
means of a nonperturbative implementation of the Ball-Chiu construction; the
latter, in its original form, involves the inverse gluon propagator, the ghost
dressing function, and certain form factors of the ghost-gluon kernel. The main
conceptual subtlety that renders this endeavor nontrivial is the infrared
finiteness of the gluon propagator, and the resulting need to separate the
vertex into two pieces, one that is intimately connected with the emergence of
a gluonic mass scale, and one that satisfies the original set of Slavnov-Taylor
identities, but with the inverse gluon propagator replaced by its "kinetic"
term. The longitudinal form factors obtained by this construction are presented
for arbitrary Euclidean momenta, as well as special kinematic configurations,
parametrized by a single momentum. A particularly preeminent feature of the
components comprising the tree-level vertex is their considerable suppression
for momenta below 1 GeV, and the appearance of the characteristic
"zero-crossing" in the vicinity of 100-200 MeV. Special combinations of the
form factors derived with this method are compared with the results of recent
large-volume lattice simulations as well as Schwinger-Dyson equations, and good
overall agreement is found. A variety of issues related to the distribution of
the pole terms responsible for the gluon mass generation are discussed in
detail, and their impact on the structure of the transverse parts is
elucidated. In addition, a brief account of several theoretical and
phenomenological possibilities involving these newly acquired results is
presented.Comment: 55 pages, 18 figure
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