2,631 research outputs found
Stable skyrmions from extra dimensions
We show that skyrmions arising from compact five dimensional models have
stable sizes. We numerically obtain the skyrmion configurations and calculate
their size and energy. Although their size strongly depends on the magnitude of
localized kinetic-terms, their energy is quite model-independent ranging
between 50-65 times F_pi^2/m_rho, where F_pi is the Goldstone decay constant
and m_rho the lowest Kaluza-Klein mass. These skyrmion configurations
interpolate between small 4D YM instantons and 4D skyrmions made of Goldstones
and a massive vector boson. Contrary to the original 4D skyrmion and previous
5D extensions, these configurations have sizes larger than the inverse of the
cut-off scale and therefore they are trustable within our effective 5D
approach. Such solitonic particles can have interesting phenomenological
consequences as they carry a conserved topological charge analogous to baryon
number.Comment: 20 pages, 3 figure
Massive Pions, Anomalies and Baryons in Holographic QCD
We consider a holographic model of QCD, obtained by a very simple
modification of the original construction, which describes at the same time the
pion mass, the QCD anomalies and the baryons as topological solitons. We study
in detail its phenomenological implications in both the mesonic and baryonic
sectors and compare with the observations.Comment: 31 pages, 2 figures; v2: Version published in Nucl. Phys.
The Electroweak phase transition in models with gauge-Higgs unification
The dynamics of five dimensional Wilson line phases at finite temperature is studied in the oneloop approximation. We show that at temperatures of order T 3c 1/L, where L is the length of
the compact space, the gauge symmetry is always restored and the electroweak phase transition
appears to be of first order.
We focus on a specific model where the Wilson line phase is identified with the Higgs field
(gauge-Higgs unification). The transition is of first order even for values of the Higgs mass above
the current experimental limit. If large localized gauge kinetic terms are present, the transition
might be strong enough to give baryogenesis at the electroweak transitio
Finite Gluon Fusion Amplitude in the Gauge-Higgs Unification
We show that the gluon fusion amplitude in the gauge-Higgs unification
scenario is finite in any dimension regardless of its nonrenormalizability.
This result is supported by the fact that the local operator describing the
gluon fusion process is forbidden by the higher dimensional gauge invariance.
We explicitly calculate the gluon fusion amplitude in an arbitrary dimensional
gauge-Higgs unification model and indeed obtain the finite result.Comment: 15 pages, final version to appear in MPL
Observation of Horizontal Air Showers with ARGO-YBJ
Abstract A preliminary analysis of Extensive Air Showers reconstructed by ARGO-YBJ with zenith angle greater than 80° is reported. The measurement of the size spectrum and of the azimuthal distribution is discussed. A description of the topology of these events is also provided
Simple and Realistic Composite Higgs Models in Flat Extra Dimensions
We construct new composite Higgs/gauge-Higgs unification (GHU) models in flat
space that overcome all the difficulties found in the past in attempting to
construct models of this sort. The key ingredient is the introduction of large
boundary kinetic terms for gauge (and fermion) fields. We focus our analysis on
the electroweak symmetry breaking pattern and the electroweak precision tests
and show how both are compatible with each other. Our models can be seen as
effective TeV descriptions of analogue warped models. We point out that, as far
as electroweak TeV scale physics is concerned, one can rely on simple and more
flexible flat space models rather than considering their unavoidably more
complicated warped space counterparts. The generic collider signatures of our
models are essentially undistinguishable from those expected from composite
Higgs/warped GHU models, namely a light Higgs, colored fermion resonances below
the TeV scale and sizable deviations to the Higgs and top coupling.Comment: 30 figures, 9 figures; v2: minor improvements, one reference added,
version to appear in JHE
Experimental performance comparison between circular and elliptical tubes in evaporative condensers
In refrigeration systems, evaporative condensers have two main advantages compared to other condensation heat exchangers: They operate at lower condensation temperature than traditional air-cooled condensers and require a lower quantity of water and pumping power compared to evaporative towers. The heat and mass transfer that occur on tube batteries are difficult to study. The aim of this work is to apply an experimental approach to investigate the performance of an evaporative condenser on a reduced scale by means of a test bench, consisting of a transparent duct with a rectangular test section in which electric heaters, inside elliptical pipes (major axis 32 mm, minor axis 23 mm), simulate the presence of the refrigerant during condensation. By keeping the water conditions fixed and constant, the operating conditions of the air and the inclination of the heat transfer geometry were varied, and this allowed to carry out a sensitivity analysis, depending on some of the main parameters that influence the thermo-fluid dynamic phenomena, as well as a performance comparison. The results showed that the heat transfer increases with the tube surface exposed directly to the air as a result of the increase in their inclination, that has been varied in the range 0–20°. For the investigated conditions, the average increase, resulting by the inclination, is 28%
Effective theoretical approach of Gauge-Higgs unification model and its phenomenological applications
We derive the low energy effective theory of Gauge-Higgs unification (GHU)
models in the usual four dimensional framework. We find that the theories are
described by only the zero-modes with a particular renormalization condition in
which essential informations about GHU models are included. We call this
condition ``Gauge-Higgs condition'' in this letter. In other wards, we can
describe the low energy theory as the SM with this condition if GHU is a model
as the UV completion of the Standard Model. This approach will be a powerful
tool to construct realistic models for GHU and to investigate their low energy
phenomena.Comment: 18 pages, 2 figures; Two paragraphs discussing the applicable scope
of this approach are adde
Ethical issues in assistive ambient living technologies for ageing well
Assistive Ambient Living (AAL) in ageing refers to any device used to support ageing related psychological and physical changes aimed at improving seniors’ quality of life and reducing caregivers’ burdens. The diffusion of these devices opens the ethical issues related to their use in the human personal space. This is particularly relevant when AAL technologies are devoted to the ageing population that exhibits special bio-psycho-social aspects and needs. In spite of this, relatively little research has focused on ethical issues that emerge from AAL technologies. The present article addresses ethical issues emerging when AAL technologies are implemented for assisting the elderly population and is aimed at raising awareness of these aspects among healthcare providers. The overall conclusion encourages a person-oriented approach when designing healthcare facilities. This process must be fulfilled in compliance with the general principles of ethics and individual nature of the person devoted to. This perspective will develop new research paradigms, paving the way for fulfilling essential ethical principles in the development of future generations of personalized AAL devices to support ageing people living independently at their home
Weak Mixing Angle and Higgs Mass in Gauge-Higgs Unification Models with Brane Kinetic Terms
We show that the idea of Gauge-Higgs unification(GHU) can be rescued from the
constraint of weak mixing angle by introducing localized brane kinetic terms in
higher dimensional GHU models with bulk and simple gauge groups. We find that
those terms lead to a ratio between Higgs and W boson masses, which is a little
bit deviated from the one derived in the standard model. From numerical
analysis, we find that the current lower bound on the Higgs mass tends to
prefer to exceptional groups E(6), E(7), E(8) rather than other groups like
SU(3l), SO(2n+1), G(2), and F(4) in 6-dimensional(D) GHU models irrespective of
the compactification scales. For the compactification scale below 1 TeV, the
Higgs masses in 6D GHU models with SU(3l), SO(2n+1), G(2), and F(4) groups are
predicted to be less than the current lower bound unless a model parameter
responsible for re-scaling SU(2) gauge coupling is taken to be unnaturally
large enough. To see how the situation is changed in more higher dimensional
GHU model, we take 7D S^{3}/ Z_{2} and 8D T^{4}/ Z_{2} models. It turns out
from our numerical analysis that these higher dimensional GHU models with gauge
groups except for E(6) can lead to the Higgs boson whose masses are predicted
to be above the current lower bound only for the compatification scale above 1
TeV without taking unnaturally large value of the model parameter, whereas the
Higgs masses in the GHU models with E(6) are compatible with the current lower
bound even for the compatification scale below 1 TeV.Comment: 22 pages, 4 figure
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