948 research outputs found
Psammomermis sericesthidis n. sp. (Nematoda : Mermithidae) : a parasitoid of pasture feeding scarab larvae (Coleoptera : Scarabaeidae) in southeastern Australia
#Psammomernis sericesthidis n. sp. est un parasitoĂŻde des larves des scarabĂ©s, #Sericesthis geminata Boisduval, #S. nigrolineata (Boisduval) (#Melolonthinae), #Dasygnathus sp., #Anoplognathus sp. (#Rutelinae), #Heteronyx sp. and #Anomalomorpha sp. (#Dynastinae) dans la rĂ©gion des plateaux du sud-est australien. #P. sericesthidis n. sp. se distingue de toutes les espĂšces dĂ©crites dans le genre - sauf #P. aricephala Ipatjeva et Pimenova, 1985 - par la prĂ©sence d'un seul ergot hypodermique cĂ©phalique. #P. sericesthidis n. sp. diffĂšre de #P. aricephala par la forme de la tĂȘte, la taille et la position des amphides, et la taille beaucoup plus grande du corps. (RĂ©sumĂ© d'auteur
Gluino Pair Production at Linear e^+e^- Colliders
We study the potential of high-energy linear colliders for the
production of gluino pairs within the Minimal Supersymmetric Standard Model
(MSSM). In this model, the process is mediated by
quark/squark loops, dominantly of the third generation, where the mixing of
left- and right-handed states can become large. Taking into account realistic
beam polarization effects, photon and -boson exchange, and current mass
exclusion limits, we scan the MSSM parameter space for various
center-of-mass energies to determine the regions, where gluino production
should be visible.Comment: 22 pages, 9 figure
Time Delay Effects on Coupled Limit Cycle Oscillators at Hopf Bifurcation
We present a detailed study of the effect of time delay on the collective
dynamics of coupled limit cycle oscillators at Hopf bifurcation. For a simple
model consisting of just two oscillators with a time delayed coupling, the
bifurcation diagram obtained by numerical and analytical solutions shows
significant changes in the stability boundaries of the amplitude death, phase
locked and incoherent regions. A novel result is the occurrence of amplitude
death even in the absence of a frequency mismatch between the two oscillators.
Similar results are obtained for an array of N oscillators with a delayed mean
field coupling and the regions of such amplitude death in the parameter space
of the coupling strength and time delay are quantified. Some general analytic
results for the N tending to infinity (thermodynamic) limit are also obtained
and the implications of the time delay effects for physical applications are
discussed.Comment: 20 aps formatted revtex pages (including 13 PS figures); Minor
changes over the previous version; To be published in Physica
Dynamics of a Limit Cycle Oscillator under Time Delayed Linear and Nonlinear Feedbacks
We study the effects of time delayed linear and nonlinear feedbacks on the
dynamics of a single Hopf bifurcation oscillator. Our numerical and analytic
investigations reveal a host of complex temporal phenomena such as phase slips,
frequency suppression, multiple periodic states and chaos. Such phenomena are
frequently observed in the collective behavior of a large number of coupled
limit cycle oscillators. Our time delayed feedback model offers a simple
paradigm for obtaining and investigating these temporal states in a single
oscillator.We construct a detailed bifurcation diagram of the oscillator as a
function of the time delay parameter and the driving strengths of the feedback
terms. We find some new states in the presence of the quadratic nonlinear
feedback term with interesting characteristics like birhythmicity, phase
reversals, radial trapping, phase jumps and spiraling patterns in the amplitude
space. Our results may find useful applications in physical, chemical or
biological systems.Comment: VERSION 4: Fig. 10(d) added, an uncited reference removed; (To appear
in Physica D) (17 pages, 21 figures, two column, aps RevTeX); VERSION 3:
Revised. In Section 2, small tau approximation added; Section 3 is divided
into subsections; periodic solution discussed in detail; Figs. 7 and 11
discarded; Figs. 12 and 14 altered; three new figures (now Figs. 10, 11 and
21) added. VERSION 2: Figs. 1 and 2 replace
Z decays into light gluinos: a calculation based on unitarity
The Z boson can decay to a pair of light gluinos through loop-mediated
processes. Based on unitarity of the S-matrix, the imaginary part of the decay
amplitude is computed in the presence of a light bottom squark. This imaginary
part can provide useful information on the full amplitude. Implications are
discussed for a recently proposed light gluino and light bottom squark
scenario.Comment: 19 pages, LaTeX, 3 figures, submitted to Phys. Rev.
Gluino Production in Electron-Positron Annihilation
We discuss the pair production of gluinos in electron-positron annihilation
at LEP, in a model with soft supersymmetry breaking, allowing for mixing
between the squarks. In much of the parameter space of the Minimal
Supersymmetric Model (MSSM) the cross section corresponds to a branching
ratio above , even up to . A non-observation of gluinos at
this level restricts the allowed MSSM parameter space. In particular, it leads
to lower bounds on the soft mass parameters in the squark sector.Comment: 24 pages LATEX plus 10 pages of figures (not included, available on
request). Full postscript version available by anonymous ftp at node
VSFYS1.FI.UIB.NO in subdirectory OSLAND, file BERGEN94-10.PS), Bergen
Scientific/Technical Report No. 1994-1
SO(10) unified models and soft leptogenesis
Motivated by the fact that, in some realistic models combining SO(10) GUTs
and flavour symmetries, it is not possible to achieve the required baryon
asymmetry through the CP asymmetry generated in the decay of right-handed
neutrinos, we take a fresh look on how deep this connection is in SO(10). The
common characteristics of these models are that they use the see-saw with
right-handed neutrinos, predict a normal hierarchy of masses for the neutrinos
observed in oscillating experiments and in the basis where the right-handed
Majorana mass is diagonal, the charged lepton mixings are tiny.
In addition these models link the up-quark Yukawa matrix to the neutrino
Yukawa matrix Y^\nu with the special feature of Y^\nu_{11}-> 0 Using this
condition, we find that the required baryon asymmetry of the Universe can be
explained by the soft leptogenesis using the soft B parameter of the second
lightest right-handed neutrino whose mass turns out to be around 10^8 GeV. It
is pointed out that a natural way to do so is to use no-scale supergravity
where the value of B ~1 GeV is set through gauge-loop corrections.Comment: 26 pages, 2 figures. Added references, new appendix of a relevant fit
and improved comment
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