473 research outputs found
Non-Abelian Wilson Surfaces
A definition of non-abelian genus zero open Wilson surfaces is proposed. The
ambiguity in surface-ordering is compensated by the gauge transformations.Comment: JHEP Latex, 10 pages, 6 figures; v2, refs and comments added in sec.
Glueball Spin
The spin of a glueball is usually taken as coming from the spin (and possibly
the orbital angular momentum) of its constituent gluons. In light of the
difficulties in accounting for the spin of the proton from its constituent
quarks, the spin of glueballs is reexamined. The starting point is the
fundamental QCD field angular momentum operator written in terms of the
chromoelectric and chromomagnetic fields. First, we look at the restrictions
placed on the structure of glueballs from the requirement that the QCD field
angular momentum operator should satisfy the standard commutation
relationships. This can be compared to the electromagnetic charge/monopole
system, where the quantization of the field angular momentum places
restrictions (i.e. the Dirac condition) on the system. Second, we look at the
expectation value of this operator under some simplifying assumptions.Comment: 11 pages, 0 figures; added references and some discussio
Challenges and opportunities in late-stage chronic kidney disease
There is increasing recognition that chronic diseases are a major challenge for health delivery systems and treasuries. These are highly prevalent and costly diseases and frequency is expected to increase greatly as the population of many countries ages. Chronic kidney disease (CKD) has not received the same attention as other chronic diseases such as congestive heart failure; yet, the prevalence and costs of CKD are substantial. Greater recognition and support for CKD may require that the disease no longer be viewed as one continuous disease state. Early CKD stages require less complex care and generate lower costs. In contrast, late-stage CKD is every bit as complex and costly as other major chronic diseases. Health authorities may not recognize and fund CKD care appropriately until late-stage CKD is defined clearly as separate and distinct from earlier stages of disease. In this review, we describe the burden of chronic diseases, consider the challenges and barriers and propose processes to improve late-stage CKD care. In particular, we recommend the need for improved continuity of care, enhanced use of information technology, multidisciplinary care, timely referral to nephrologists, protocol use and improved patient engagement
Resolution of the Klein Paradox
We present a resolution of the Klein paradox within the framework of
one-particle relativistic quantum mechanics. Not only reflection becomes total
but the vacuum remains neutral as well. This is accomplished by replacing the
pair production process with virtual negative energy "incidence" within the
barrier in a similar manner to what is done with image charges in electrostatic
and virtual sources in optics.Comment: 9 pages, 8 figure
Color dielectric model with two scalar fields
SU(2) Yang-Mills theory coupled in a non-minimal way to two scalar fields is
discussed. For the massless scalar fields a family of finite energy solutions
generated by an external, static electric charge is found. Additionally, there
is a single solution which can be interpreted as confining one. Similar
solutions have been obtained in the magnetic sector. In case of massive scalar
fields the Coulomb problem is investigated. We find that asymptotic behavior of
the fields can also, for some values of the parameter of the model, give
confinement of the electric charge. Quite interesting one glueball--meson
coupling gives the linear confining potential. Finally, it is shown that for
one non-dynamical scalar field we derive the color dielectric generalization of
the Pagels--Tomboulis model.Comment: 20 pages, LaTeX, Accepted for publication in Eur. Phys. J.
Working with simple machines
A set of examples is provided that illustrate the use of work as applied to
simple machines. The ramp, pulley, lever and hydraulic press are common
experiences in the life of a student and their theoretical analysis therefore
makes the abstract concept of work more real. The mechanical advantage of each
of these systems is also discussed so that students can evaluate their
usefulness as machines.Comment: 9 pages, 4 figure
On Neutrinos and Fermionic Mass Patterns
Recent data on neutrino mass differences are consistent with a hierarchical
neutrino mass structure strikingly similar to what is observed for the other
fermionic masses.Comment: 8pages, 2figure
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