999 research outputs found
Asymptotic freedom in a scalar field theory on the lattice
An alternative model to the trivial -theory of the standard model of
weak interactions is suggested, which embodies the Higgs-mechanism, but is free
of the conceptual problems of standard -theory. We propose a
N-component, O(N)-symmetric scalar field theory, which is originally defined on
the lattice. The model can be motivated from SU(2) gauge theory. Thereby the
scalar field arises as a gauge invariant degree of freedom. The scalar lattice
model is analytically solved in the large N limit. The continuum limit is
approached via an asymptotically free scaling. The renormalized theory evades
triviality, and furthermore gives rise to a dynamically formed mass of the
scalar particle.Comment: 10 pages, LaTeX, one figure and a motivation for the particular type
of action adde
Letter from Henry K. Abbot to John Muir, 1896 Nov 4.
No. 23 Berkeley St. Cambridge, MassNovember 4 1896My dear Sir:I was greatly pleased to receive your pleasant letter of 14th ult. It reminded me of so many incidents of our long trip that I could wish it were beginning instead of ended. I brought back one live capture that has already given much pleasure to my mother,now ninety seven years old. I mean your book. Her eye sight is so affected that she depends on loud reading for amusement,and certain of the Chapters, especially those on the Douglas Squirrel and the Water Ouzel have filled her with interest and delight. The storm in the forest,and the adventures inthe high Sierra so acted on her imagination that she says you must be made of iron. I knew tte book would delight her when I read it on our journey, and when you write out the little dog story you may be sure it will be appreciated.We were much hurried by threatened snow in Colorado,as we feared,and had to give up the visitto the reservation near Santa Fe. Still we saw a great deal of interesting country quite different from that more to the West. The game is abundant in Colirado. On one day\u27s drive of seventy miles we saw thirty eight deer. They were passing in droves from the high-lands of the Upper White River toward Utah. One party of seven had crossed the trail a mile or so in front of us, and were winding up the ridge beyond when suddenly they stopped, looked for a moment and then recrossed the trail with leaps and bounds which you can easily imagine. On reaching the spot we saw two huge wolves on their track,evidently in wait for prey. It is a wild free silver country. One pleasant gentleman, one of the State game wardens who accompanied us two or three days and gave us much information, was shot two days after we left him at his home, Meeker, by a party of bank robbers who were raiding the town in broad day light. He is reported dangerously wounded. We went up Pike\u27s Peak (never mind exactly how) and on the whole did more than I expected considering how far the seasonwas advanced. I spent a week in Milwaukee on the way Eastward,and am now in the land of clouds and dull days. Sargent and I are going to Washington in a few days to make arrangements for the final report. We have had one full meeting of the Commission since our return, at which both Agassiz and our President, Dr Gibbs were present; and now comes the prose following so much poetry and pleasure. I wish we could call on your pen to help us out.One thing I do enjoy. It is the presence of my type writer. If you have never taken up the use of this invention, do so at once. It is a real luxury.I saw Brewer the other day, looking perfectly well. Sargent says he went to bed for a couple of days after getting home to rest, but he is now livel as ever. All would send regards did they know I am writing.Yours very sincerelyMr.John MuirMartinez Cal
Exact Baryon, Strangeness and Charge Conservation in Hadronic Gas Models
Relativistic heavy ion collisions are studied assuming that particles can be
described by a hadron gas in thermal and chemical equilibrium. The exact
conservation of baryon number, strangeness and charge are explicitly taken into
account. For heavy ions the effect arising from the neutron surplus becomes
important and leads to a substantial increase in e.g. the ratio.
A method is developed which is very well suited for the study of small systems.Comment: 5 pages, 5 Postscript figure
Centimetre continuum emission from young stellar objects in Cederblad 110
The low-mass star formation region associated with the reflection nebula
Cederblad 110 in the Chamaeleon I cloud was mapped with the Australian
Telescope Compact Array (ATCA) at 6 and 3.5cm. Altogether 11 sources were
detected, three of which are previously known low mass young stellar objects
associated with the nebula: the illuminating star IRS2 (Class III, Einstein
X-ray source CHX7), the brightest far-infrared source IRS4 (Class I), and the
weak X-ray source CHX10a (Class III). The other young stellar objects in the
region, including the Class 0 protostar candidate Cha-MMS1, were not detected.
The radio spectral index of IRS4 (alpha = 1.7 +/- 0.3) is consistent with
optically thick free-free emission arising from a dense ionized region,
probably a jet-induced shock occurring in the circumstellar material. As the
only Class I protostar with a 'thermal jet' IRS4 is the strongest candidate for
the central source of the molecular outflow found previously in the region. The
emission from IRS2 has a flat spectrum (alpha = 0.05 +/- 0.05) but shows no
sign of polarization, and therefore its origin is likely to be optically thin
free-free emission either from ionized wind or a collimated jet. The strongest
source detected in this survey is a new compact object with a steep negative
spectral index (-1.1) and a weak linear polarization (about 2 %), which
probably represents a background radio galaxy.Comment: 7 pages, 2 Postscript figures. Accepted for publication in Astronomy
& Astrophysic
Towards an evidence-based approach to fostering collaborative conversation in mainstream primary classrooms: Response to commentators
The ability to engage with ease in collaborative conversation is critical for child well-being and development. While key underpinning skills are biologically enabled, children require appropriate scaffolding and practice opportunities to develop proficient social conversational ability. Teaching conversation skills is a statutory requirement of the English primary (and many other) curricula. However, currently most upper primary mainstream teachers are not trained to teach conversation skills and do not teach them in the classroom or provide time for children to practice. We argue for first steps towards an evidence-based approach for a universal/Tier 1 programme, while fully acknowledging an ongoing need for Tier 2 and Tier 3 support as well as for further research into the strategies which are most effective in Tier 2/3 contexts. Further research is also needed to explore cultural variation in social conversation and to develop reliable, valid and brief teacher measures of child social conversational ability
On the relation between effective supersymmetric actions in different dimensions
We make two remarks: (i) Renormalization of the effective charge in a
4--dimensional (supersymmetric) gauge theory is determined by the same graphs
and is rigidly connected to the renormalization of the metric on the moduli
space of the classical vacua of the corresponding reduced quantum mechanical
system. Supersymmetry provides constraints for possible modifications of the
metric, and this gives us a simple proof of nonrenormalization theorems for the
original 4-dimensional theory. (ii) We establish a nontrivial relationship
between the effective (0+1)-dimensional and (1+1)-dimensional Lagrangia (the
latter represent conventional
Kahlerian sigma models).Comment: 15 pages, 2 figure
Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data
In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational-wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95% confidence level upper limits have been computed assuming both that polarization parameters are completely unknown and that they are known with some uncertainty, as derived from x-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of 2 below the spin-down limit, and represent a significant improvement with respect to past analysis. This is the first time the spin-down limit is significantly overcome in a narrow-band search.Fil: Quiroga, Gonzalo Damián. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Relatividad y Gravitacion; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Maglione, Cesar German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Relatividad y Gravitacion; ArgentinaFil: Reula, Oscar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Relatividad y Gravitacion; ArgentinaFil: Aasi, J.. California Institute of Technology; Estados UnidosFil: Abbot, B. P.. California Institute of Technology; Estados UnidosFil: Abbot, R.. California Institute of Technology; Estados UnidosFil: Abbot, T.. State University of Louisiana; Estados UnidosFil: Abernathy, M. R.. California Institute of Technology; Estados UnidosFil: Acernese, F.. Universita di Salerno; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Ackley, K.. University of Florida; Estados UnidosFil: Adams, C.. LIGO Livingston Observatory; Estados UnidosFil: Adams, T.. Universite de Savoie. Laboratoire d’Annecy-le-Vieux de Physique des Particules; Francia. Cardiff University; Reino UnidoFil: Adams, T.. Universite de Savoie. Laboratoire d’Annecy-le-Vieux de Physique des Particules; FranciaFil: Addesso, P.. University of Sannio at Benevento; ItaliaFil: Adhikar, R. X.. California Institute of Technology; Estados UnidosFil: Adya, V.. Max-Planck-Institut für Gravitationsphysik; AlemaniaFil: Affeldt, C.. Max-Planck-Institut für Gravitationsphysik; AlemaniaFil: Agathos, M.. Nikhef; Science Park; Países BajosFil: Agatsuma, K.. Nikhef; Science Park; Países BajosFil: Aggarwal, N.. Massachusetts Institute of Technology; Estados UnidosFil: Aguiar, O. D.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Ain, A.. Inter-University Centre for Astronomy and Astrophysics; IndiaFil: Ajith, P.. Tata Institute of Fundamental Research; IndiaFil: Alemic, A.. Syracuse University; Estados UnidosFil: Allen, B.. Max-Planck-Institut für Gravitationsphysik; Alemania. University of Wisconsin; Estados UnidosFil: Allocca, A.. Università degli Studi di Siena; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Amariutei, D.. University of Florida; Estados UnidosFil: Anderson, S. B.. California Institute of Technology; Estados UnidosFil: Anderson, W. G.. University of Wisconsin; Estados UnidosFil: Arai, K.. California Institute of Technology; Estados Unido
On the exact conservation laws in thermal models and the analysis of AGS and SIS experimental results
The production of hadrons in relativistic heavy ion collisions is studied
using a statistical ensemble with thermal and chemical equilibrium. Special
attention is given to exact conservation laws, i.e. certain charges are treated
canonically instead of using the usual grand canonical approach. For small
systems, the exact conservation of baryon number, strangeness and electric
charge is to be taken into account. We have derived compact, analytical
expressions for particle abundances in such ensemble. As an application, the
change in ratios in AGS experiments with different interaction system
sizes is well reproduced. The canonical treatment of three charges becomes
impractical very quickly with increasing system size. Thus, we draw our
attention to exact conservation of strangeness, and treat baryon number and
electric charge grand canonically. We present expressions for particle
abundances in such ensemble as well, and apply them to reproduce the large
variety of particle ratios in GSI SIS 2 A GeV Ni-Ni experiments. At the
energies considered here, the exact strangeness conservation fully accounts for
strange particle suppression, and no extra chemical factor is needed.Comment: Talk given at Strangeness in Quark Matter '98, Padova, Italy (1998).
Submitted to J.Phys. G. 5 pages, 2 figure
Long term study of the seismic environment at LIGO
The LIGO experiment aims to detect and study gravitational waves using ground
based laser interferometry. A critical factor to the performance of the
interferometers, and a major consideration in the design of possible future
upgrades, is isolation of the interferometer optics from seismic noise. We
present the results of a detailed program of measurements of the seismic
environment surrounding the LIGO interferometers. We describe the experimental
configuration used to collect the data, which was acquired over a 613 day
period. The measurements focused on the frequency range 0.1-10 Hz, in which the
secondary microseismic peak and noise due to human activity in the vicinity of
the detectors was found to be particularly critical to interferometer
performance. We compare the statistical distribution of the data sets from the
two interferometer sites, construct amplitude spectral densities of seismic
noise amplitude fluctuations with periods of up to 3 months, and analyze the
data for any long term trends in the amplitude of seismic noise in this
critical frequency range.Comment: To be published in Classical and Quantum Gravity. 24 pages, 15
figure
Towards an evidence-based approach to fostering collaborative conversation in mainstream primary classrooms: Response to commentators
The ability to engage with ease in collaborative conversation is critical for child well-being and development. While key underpinning skills are biologically enabled, children require appropriate scaffolding and practice opportunities to develop proficient social conversational ability. Teaching conversation skills is a statutory requirement of the English primary (and many other) curricula. However, currently most upper primary mainstream teachers are not trained to teach conversation skills and do not teach them in the classroom or provide time for children to practice. We argue for first steps towards an evidence-based approach for a universal/Tier 1 programme, while fully acknowledging an ongoing need for Tier 2 and Tier 3 support as well as for further research into the strategies which are most effective in Tier 2/3 contexts. Further research is also needed to explore cultural variation in social conversation and to develop reliable, valid and brief teacher measures of child social conversational ability
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