870 research outputs found
Gluon confinement criterion in QCD
We fix exactly and uniquely the infrared structure of the full gluon
propagator in QCD, not solving explicitly the corresponding dynamical equation
of motion. By construction, this structure is an infinite sum over all possible
severe (i.e., more singular than ) infrared singularities. It reflects
the zero momentum modes enhancement effect in the true QCD vacuum, which is due
to the self-interaction of massless gluons. It existence automatically exhibits
a characteristic mass (the so-called mass gap). It is responsible for the scale
of nonperturbative dynamics in the true QCD ground state. The theory of
distributions, complemented by the dimensional regularization method, allows
one to put the severe infrared singularities under the firm mathematical
control. By an infrared renormalization of a mass gap only, the infrared
structure of the full gluon propagator is exactly reduced to the simplest
severe infrared singularity, the famous . Thus we have exactly
established the interaction between quarks (concerning its pure gluon (i.e.,
nonlinear) contribution) up to its unimportant perturbative part. This also
makes it possible for the first time to formulate the gluon confinement
criterion and intrinsically nonperturbative phase in QCD in a manifestly
gauge-invariant ways.Comment: 10 pages, no figures, no tables. Typos corrected and the
clarification is intoduced. Shorten version to appear in Phys. Lett.
Genetic and Biochemical Characterization of the Oligopeptide Transport System of Lactococcus lactis
Postgraduate Spotlights:Using a Community of Inquiry approach to enhance student engagement in geographical higher education
While the majority of pedagogical practice has been affected by the COVID-19 pandemic, the teaching of geographical research skills has been especially difficult with the loss of fieldwork and practical applications. Furthermore, the move to online teaching has diminished the learning communities in face-to-face classrooms. In an attempt to counteract these issues, this paper reflects on a learning activity in an undergraduate geographical research methods course, âPostgraduate Spotlightsâ where two postgraduate researchers presented their specialist research methods followed by an interactive question-and-answer session with the undergraduates. We (as postgraduates, undergraduates and teaching staff) found that the open and critical discussion in the workshop fostered a Community of Inquiry that encouraged engagement from students stimulating their curiosity about geographical research methods. Through our discussion, we demonstrate the importance of having postgraduate researchers involved in teaching, as Graduate Teaching Assistants (GTAs) given their liminal role of researcher-learner. We also emphasise the importance of letting the students lead their own learning, building a Community of Inquiry across academic stages, and creating a constructive dialogue around geographical research methods. While the reproducibility of the workshop face-to-face remains to be seen, this article emphasises the potential for applying such an approach to stimulate free-flowing discussion and ultimately promote a Community of Inquiry
Postgraduate Spotlights:Using a Community of Inquiry approach to enhance student engagement in geographical higher education
Postgraduate Spotlights:Using a Community of Inquiry approach to enhance student engagement in geographical higher education
Postgraduate Spotlights:Using a Community of Inquiry approach to enhance student engagement in geographical higher education
Postgraduate Spotlights:Using a Community of Inquiry approach to enhance student engagement in geographical higher education
The non-Abelian Interferometer
We consider the tunneling current through a double point-contact Fabry-Perot
interferometer such as used in recent experimental studies of the fractional
quantum Hall plateau at filling fraction nu=5/2. We compare the predictions of
several different models of the state of the electrons at this plateau: the
Moore-Read, anti-Pfaffian, SU(2)_2 NAF, K=8 strong pairing, and (3,3,1) states.
All of these predict the existence of charge e/4 quasiparticles, but the first
three are non-Abelian while the last two are Abelian. We give explicit formulas
for the scaling of charge e/2 and charge e/4 quasiparticle contributions to the
current as a function of temperature, gate voltage and distance between the two
point contacts for all three models. Based on these, we analyze several
possible explanations of two phenomena reported for recent experiments by
Willett et al., namely halving of the period of the observed resistance
oscillations with rising temperature and alternation between the same two
observed periods at low temperatures as the area of the interference loop is
varied with a side gate. We conclude that the most likely explanation is that
the observed alternation is due to switching between even and odd numbers of
charge e/4 quasiparticles enclosed within the loop as a function of side gate
voltage, which is a clear signature of the presence of non-Abelian anyons.
However, there are important features of the data which do not have a simple
explanation within this picture. We suggest further experiments which could
help rule out some possible scenarios. We make the corresponding predictions
for future tunneling and interference experiments at the other observed second
Landau level fractional quantum Hall states.Comment: 15 pages, 1 figure; v2: additional discussions and references added;
v3: clarifications and references updated; Appendix C has been removed and
incorporated in arXiv:0909.1056; this paper has been given the more clear,
accurate, and informative title "Interferometric signature of non-Abelian
anyons" in PRB by its editor
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