1,721 research outputs found
Eviction of a 125 GeV "heavy"-Higgs from the MSSM
We prove that the present experimental constraints are already enough to rule
out the possibility of the ~125 GeV Higgs found at LHC being the second
lightest Higgs in a general MSSM context, even with explicit CP violation in
the Higgs potential. Contrary to previous studies, we are able to eliminate
this possibility analytically, using simple expressions for a relatively small
number of observables. We show that the present LHC constraints on the diphoton
signal strength, tau-tau production through Higgs and BR(B -> X_s gamma) are
enough to preclude the possibility of H_2 being the observed Higgs with m_H~125
GeV within an MSSM context, without leaving room for finely tuned
cancellations. As a by-product, we also comment on the difficulties of an MSSM
interpretation of the excess in the gamma-gamma production cross section
recently found at CMS that could correspond to a second Higgs resonance at
m_H~136 GeV.Comment: 38 pages, 9 figures. Final version accepted at JHEP. Sections 2, 3
and appendices simplified. Experimental results updated, several references
added. Small typos corrected and a new comparison of approximate formulas
with full expressions include
Zero-point quantum swing of magnetic couples
Quantum fluctuations are ubiquitous in physics. Ranging from conventional
examples like the harmonic oscillator to intricate theories on the origin of
the universe, they alter virtually all aspects of matter -- including
superconductivity, phase transitions and nanoscale processes. As a rule of
thumb, the smaller the object, the larger their impact. This poses a serious
challenge to modern nanotechnology, which aims total control via atom-by-atom
engineered devices. In magnetic nanostructures, high stability of the magnetic
signal is crucial when targeting realistic applications in information
technology, e.g. miniaturized bits. Here, we demonstrate that zero-point
spin-fluctuations are paramount in determining the fundamental magnetic
exchange interactions that dictate the nature and stability of the magnetic
state. Hinging on the fluctuation-dissipation theorem, we establish that
quantum fluctuations correctly account for the large overestimation of the
interactions as obtained from conventional static first-principles frameworks,
filling in a crucial gap between theory and experiment [1,2]. Our analysis
further reveals that zero-point spin-fluctuations tend to promote the
non-collinearity and stability of chiral magnetic textures such as skyrmions --
a counter-intuitive quantum effect that inspires practical guidelines for
designing disruptive nanodevices
Origin of non-keplerian motions of masers in NGC 1068
We demonstrate that the ``sub-keplerian'' rotation curve of maser spots in
NGC 1068 can be explained by the gravitational attraction of the disc orbiting
the central black hole. Possible parameters matching observations are: black
hole mass of 12 million solar masses, disc outer edge > 1.3 pc, aspect ratio in
the range 0.003 to 0.3, surface density varying approximately as 1/R, and disc
mass of about 9.4 million solar masses. The physical conditions required for
the excitation of masers are fulfilled, and the outer disc would stand in a
gravitationally marginally stable state.Comment: 4 pages; accepted in A&A Letter
Ross 128-GL 447: A possible activity cycle for a slow-rotating fully convective star
Context. Long-term chromospheric activity in slow-rotating fully convective stars has scarcely been explored. Ross 128 (Gl 447) is a slow-rotator and inactive dM4 star that has been extensively observed. It hosts the fourth closest extrasolar planet. Aims. Ross 128 is an ideal target to test dynamo theories in slow-rotating low-mass stars. Methods. To characterize the magnetic activity of Ross 128, we studied the SK-indexes derived from CASLEO, HARPS, FEROS, UVES, and X-shooter spectra. Using the generalized Lomb-Scargle and CLEAN periodograms, we analyzed the whole SK time-series obtained between 2004 and 2018. We performed a similar analysis for the Na I-index, and we analyzed its relation with the SK-index. Results. From both indexes, we obtain a possible activity cycle with a period of about five years, which is one of a small handful of activity cycles that have been reported for a slow-rotating fully convective star.Fil: Ibañez Bustos, Romina Valeria. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Buccino, Andrea Paola. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Flores, M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Mauas, Pablo Jacobo David. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin
Tuning paramagnetic spin-excitations of single adatoms
Around 50 years ago, Doniach [Proc. Phys. Soc. 91, 86 (1967)] predicted the
existence of paramagnons in nearly ferromagnetic materials, recently measured
in bulk Pd [Phys. Rev. Lett. 105, 027207 (2010)]. Here we predict the analogous
effect for single adatoms, namely paramagnetic spin-excitations (PSE). Based on
time-dependent density functional theory, we demonstrate that these overdamped
excitations acquire a well-defined peak structure in the meV energy region when
the adatom's Stoner criterion for magnetism is close to the critical point. In
addition, our calculations reveal a subtle tunability and enhancement of PSE by
external magnetic fields, exceeding by far the response of bulk paramagnons and
even featuring the atomic version of a quantum phase transition. We further
demonstrate how PSE can be detected as moving steps in the
signal of state-of-the-art inelastic scanning tunneling spectroscopy, opening a
potential route for experimentally accessing fundamental electronic properties
of non-magnetic adatoms, such as the Stoner parameter.Comment: 6 pages, 3 figure
Colonización espontánea de taludes de desmonte sobre margas en Navarra: establecimiento y fuente de diásporas.
Tras la hidrosiembra de taludes de desmonte sobre margas en localidades
navarras con clima submediterráneo se implanta una cubierta vegetal de especies
hidrosembradas que experimenta una rápida regresión, tal y como hemos observado
en estudios previos. A pesar de ello, algunas especies autóctonas son capaces de
colonizar estas superficies. Describimos la capacidad de colonización de estas
últimas especies, cuyas diásporas proceden de la lluvia de semillas, para determinar
si también les afecta la regresión observada en las especies hidrosembradas. También
estudiamos su distribución espacial para determinar la fuente de diásporas.
A pesar de la gran dificultad para colonizar los desmontes, las especies
autóctonas no siguen el modelo regresivo que presentan las especies hidrosembradas
en desmontes de similares características en Navarra. Por otro lado, la mayoría de las
especies disminuyen su abundancia al aumentar la distancia a la zona superior del
talud, donde se encuentra la vegetación que actúa como principal fuente de diásporas
Radiative Electroweak Symmetry Breaking and the Infrared Fixed Point of the Top Quark Mass
The infrared quasi fixed point solution for the top quark mass in the Minimal
Supersymmetric Standard Model explains in a natural way large values of the top
quark mass and appears as a prediction in many interesting theoretical schemes.
Moreover, as has been recently pointed out, for moderate values of ,
in order to achieve gauge and bottom-tau Yukawa coupling unification, the top
quark mass must be within of its fixed point value. In this work we
show that the convergence of the top quark mass to its fixed point value has
relevant consequences for the (assumed) universal soft supersymmetry breaking
parameters at the grand unification scale. In particular, we show that the low
energy parameters do not depend on and but on the combination
. Hence, there is a reduction in the number of
independent parameters. Most interesting, the radiative
breaking condition implies strong correlations between the supersymmetric mass
parameter and the supersymmetry breaking parameters and
or . These correlations, which become stronger for , may have some fundamental origin, which would imply the need of a
reformulation of the naive fine tuning criteria.Comment: 17 pages, 5 figures, CERN-TH.7060/9
Avaliação de desempenho lumínico: imagens HDR
Anais do VI Encontro de Iniciação Científica e II Encontro Anual de Iniciação ao Desenvolvimento Tecnológico e Inovação – EICTI 2017 - 04 a 06 de outubro de 2017 - temática EngenhariaCom o passar do tempo e a diminuição do espaço livre, construções existentes são
adaptadas para desenvolver atividades diferentes das quais foram construídas, assim, é
comum observar ambientes com pouca iluminação para desenvolver as atividades
necessárias nos ambientes de trabalho, poiso ideal é que as decisões referentes à
iluminação natural sejam tomadas ainda na fase inicial do projeto.
Estudos de luminância analisam a qualidade de iluminação num ambiente
construído, e frequentemente estão acompanhados de novas ferramentas, como é o caso
do uso de fotografias, que permitem realizar o estudo de maneira rápida e econômica em
relação à maneira tradicional. Portanto, as imagens HDR compostas a partir de imagens
digitais podem ser utilizadas, com algumas restrições de precisão, como ferramenta para
levantamento da distribuição das luminâncias num ambiente (IBAÑEZ; ZAFRA;
SACHT, 2017)
Com base em tais informações, o presente trabalho teve como objetivo gerar
imagens de grande alcance dinâmico ou High Dynamic Range (HDR) de um ambiente, para
estudo da qualidade de iluminação e comparação com dados de medição in locoUniversidade Federal da Integração Latino-Americana (Unila); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação Araucária; Parque Tecnológico Itaipu (PTI) e Companhia de Saneamento do Paraná (SANEPAR
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