24 research outputs found
The Majorana particles and the Majorana sea
Can one make a Majorana field theory for fermions starting from the zero mass
Weyl theory, then adding a mass term as an interaction? The answer to this
question is: yes we can. We can proceed similarly to the case of the Dirac
massive field theory. In both cases one can start from the zero mass Weyl
theory and then add a mass term as an interacting term of massless particles
with a constant (external) field. In both cases the interaction gives rise to a
field theory for a free massive fermion field. We present the procedure for the
creation of a mass term in the case of the Dirac and the Majorana field and we
look for a massive field as a superposition of massless fields.Comment: 11 pages, no figure
Why Nature has made a choice of one time and three space coordinates?
We propose a possible answer to one of the most exciting open questions in
physics and cosmology, that is the question why we seem to experience four-
dimensional space-time with three ordinary and one time dimensions. We have
known for more than 70 years that (elementary) particles have spin degrees of
freedom, we also know that besides spin they also have charge degrees of
freedom, both degrees of freedom in addition to the position and momentum
degrees of freedom. We may call these ''internal degrees of freedom '' the
''internal space'' and we can think of all the different particles, like quarks
and leptons, as being different internal states of the same particle. The
question then naturally arises: Is the choice of the Minkowski metric and the
four-dimensional space-time influenced by the ''internal space''?
Making assumptions (such as particles being in first approximation massless)
about the equations of motion, we argue for restrictions on the number of space
and time dimensions. (Actually the Standard model predicts and experiments
confirm that elementary particles are massless until interactions switch on
masses.)
Accepting our explanation of the space-time signature and the number of
dimensions would be a point supporting (further) the importance of the
''internal space''.Comment: 13 pages, LaTe
Granular discharge and clogging for tilted hoppers
We measure the flux of spherical glass beads through a hole as a systematic
function of both tilt angle and hole diameter, for two different size beads.
The discharge increases with hole diameter in accord with the Beverloo relation
for both horizontal and vertical holes, but in the latter case with a larger
small-hole cutoff. For large holes the flux decreases linearly in cosine of the
tilt angle, vanishing smoothly somewhat below the angle of repose. For small
holes it vanishes abruptly at a smaller angle. The conditions for zero flux are
discussed in the context of a {\it clogging phase diagram} of flow state vs
tilt angle and ratio of hole to grain size
The flow rate of granular materials through an orifice
The flow rate of grains through large orifices
is known to be dependent on its diameter to a 5/2 power
law. This relationship has been checked for big outlet sizes,
whereas an empirical fitting parameter is needed to reproduce
the behavior for small openings. In this work, we provide
experimental data and numerical simulations covering a
wide span of outlet sizes, both in three- and two-dimensions.
This allows us to showthat the laws that are usually employed
are satisfactory only if a small range of openings is considered.
We propose a new law for the mass flow rate of grains
that correctly reproduces the data for all the orifice sizes,
including the behaviors for very large and very small outlet
sizes