8,279 research outputs found
The Elementary Particles as Quantum Knots in Electroweak Theory
We explore a knot model of the elementary particles that is compatible with
electroweak physics. The knots are quantized and their kinematic states are
labelled by , irreducible representations of , where j =
N/2, m = w/2, m' = (r+1)/2 and (N,w,r) designate respectively the number of
crossings, the writhe, and the rotation of the knot. The knot quantum numbers
(N,w,r) are related to the standard isotopic spin quantum numbers
by , where is the hypercharge. In this
model the elementary fermions are low lying states of the quantum trefoil (N=3)
and the gauge bosons are ditrefoils (N=6). The fermionic knots interact by the
emission and absorption of bosonic knots. In this framework we have explored a
slightly modified standard electroweak Lagrangian with a slightly modified
gauge group which agrees closely but not entirely with standard electroweak
theory.Comment: 29 pages; LaTex fil
Masses and Interactions of q-Fermionic Knots
The q-electroweak theory suggests a description of elementary particles as
solitons labelled by the irreducible representations of SU_q(2). Since knots
may also be labelled by the irreducible representations of SU_q(2), we study a
model of elementary particles based on a one-to-one correspondence between the
four families of Fermions (leptons, neutrinos, (-1/3) quarks, (2/3) quarks) and
the four simplest knots (trefoils). In this model the three particles of each
family are identified with the ground and first two excited states of their
common trefoil. Guided by the standard electroweak theory we calculate
conditions restricting the masses of the fermions and the interactions between
them.
In its present form the model predicts a fourth generation of fermions as
well as a neutrino spectrum. The same model with q almost equal to 1 is
compatible with the Kobayashi-Maskawa matrix. Depending on the test of these
predictions, the model may be refined.Comment: 40 pages, 2 figures, latex forma
Fine-grain process modelling
In this paper, we propose the use of fine-grain process
modelling as an aid to software development. We suggest
the use of two levels of granularity, one at the level of the
individual developer and another at the level of the
representation scheme used by that developer. The
advantages of modelling the software development process
at these two levels, we argue, include respectively: (1) the
production of models that better reflect actual
development processes because they are oriented towards
the actors who enact them, and (2) models that are
vehicles for providing guidance because they may be
expressed in terms of the actual representation schemes
employed by those actors. We suggest that our previously
published approach of using multiple âViewPointsâ to
model software development participants, the perspectives
that they hold, the representation schemes that they
deploy and the process models that they maintain, is one
way of supporting the fine-grain modelling we advocate.
We point to some simple, tool-based experiments we have
performed that support our proposition
Persistent Orbital Degeneracy in Carbon Nanotubes
The quantum-mechanical orbitals in carbon nanotubes are doubly degenerate
over a large number of states in the Coulomb blockade regime. We argue that
this experimental observation indicates that electrons are reflected without
mode mixing at the nanotube-metal contacts. Two electrons occupying a pair of
degenerate orbitals (a ``shell'') are found to form a triplet state starting
from zero magnetic field. Finally, we observe unexpected low-energy excitations
at complete filling of a four-electron shell.Comment: 6 pages, 4 figure
A numerical finite size scaling approach to many-body localization
We develop a numerical technique to study Anderson localization in
interacting electronic systems. The ground state of the disordered system is
calculated with quantum Monte-Carlo simulations while the localization
properties are extracted from the ``Thouless conductance'' , i.e. the
curvature of the energy with respect to an Aharonov-Bohm flux. We apply our
method to polarized electrons in a two dimensional system of size . We
recover the well known universal one
parameter scaling function without interaction. Upon switching on the
interaction, we find that is unchanged while the system flows toward
the insulating limit. We conclude that polarized electrons in two dimensions
stay in an insulating state in the presence of weak to moderate
electron-electron correlations.Comment: 5 pages, 4 figure
Representations of U(1,q) and Constructive Quaternion Tensor Products
The representation theory of the group U(1,q) is discussed in detail because
of its possible application in a quaternion version of the Salam-Weinberg
theory.
As a consequence, from purely group theoretical arguments we demonstrate that
the eigenvalues must be right-eigenvalues and that the only consistent scalar
products are the complex ones. We also define an explicit quaternion tensor
product which leads to a set of additional group representations for integer
``spin''.Comment: 28 pages, Latex, Dipartimento di Fisica, Universita di Lecce
INFN-Sezione di Lecc
Knots and Preons
It is shown that the four trefoil solitons that are described by the
irreducible representations D^{3/2}_{mm'} of the quantum algebra SL_q(2) (and
that may be identified with the four families of elementary fermions
(e,\mu,\tau;\nu_e\nu_\mu\nu_\tau;d,s,b;u,c,t) may be built out of three preons,
chosen from two charged preons with charges (1/3,-1/3) and two neutral preons.
These preons are Lorentz spinors and are described by the D^{1/2}_{mm'}
representation of SL_q(2). There are also four bosonic preons described by the
D^1_{mm'} and D^0_{00} representations of SL_q(2). The knotted standard theory
may be replicated at the preon level and the conjectured particles are in
principle indirectly observable.Comment: LaTex document; 12 pages; 4 table
Four-Probe Measurements of Carbon Nanotubes with Narrow Metal Contacts
We find that electrons in single-wall carbon nanotubes may propagate
substantial distances (tens of nanometers) under the metal contacts. We perform
four-probe transport measurements of the nanotube conductance and observe
significant deviations from the standard Kirchhoff's circuit rules. Most
noticeably, injecting current between two neighboring contacts on one end of
the nanotube, induces a non-zero voltage difference between two contacts on the
other end.Comment: 4 pages, 5 figures; submitte
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