8,586 research outputs found
Minkowski Spacetime and QED from Ontology of Time
Classical mechanics, relativity, electrodynamics and quantum mechanics are
often depicted as separate realms of physics, each with its own formalism and
notion. This remains unsatisfactory with respect to the unity of nature and to
the necessary number of postulates. We uncover the intrinsic connection of
these areas of physics and describe them using a common symplectic Hamiltonian
formalism. Our approach is based on a proper distinction between variables and
constants, i.e. on a basic but rigorous ontology of time. We link these concept
with the obvious conditions for the possibility of measurements. The derived
consequences put the measurement problem of quantum mechanics and the
Copenhagen interpretation of the quantum mechanical wavefunction into
perspective. According to our (onto-) logic we find that spacetime can not be
fundamental. We argue that a geometric interpretation of symplectic dynamics
emerges from the isomorphism between the corresponding Lie algebra and the
representation of a Clifford algebra. Within this conceptional framework we
derive the dimensionality of spacetime, the form of Lorentz transformations and
of the Lorentz force and fundamental laws of physics as the Planck-Einstein
relation, the Maxwell equations and finally the Dirac equation.Comment: 36 pages, 3 figures, several typos corrected, references with title
Old Game, New Rules: Rethinking The Form of Physics
We investigate the modeling capabilities of sets of coupled classical
harmonic oscillators (CHO) in the form of a modeling game. The application of
simple but restrictive rules of the game lead to conditions for an isomorphism
between Lie-algebras and real Clifford algebras. We show that the correlations
between two coupled classical oscillators find their natural description in the
Dirac algebra and allow to model aspects of special relativity, inertial
motion, electromagnetism and quantum phenomena including spin in one go. The
algebraic properties of Hamiltonian motion of low-dimensional systems can
generally be related to certain types of interactions and hence to the
dimensionality of emergent space-times. We describe the intrinsic connection
between phase space volumes of a 2-dimensional oscillator and the Dirac
algebra. In this version of a phase space interpretation of quantum mechanics
the (components of the) spinor wave-function in momentum space are abstract
canonical coordinates, and the integrals over the squared wave function
represents second moments in phase space. The wave function in ordinary
space-time can be obtained via Fourier transformation. Within this modeling
game, 3+1-dimensional space-time is interpreted as a structural property of
electromagnetic interaction. A generalization selects a series of Clifford
algebras of specific dimensions with similar properties, specifically also 10-
and 26-dimensional real Clifford algebras.Comment: 23 pages, no figure
A New Look at Linear (Non-?) Symplectic Ion Beam Optics in Magnets
We take a new look at the details of symplectic motion in solenoid and
bending magnets and rederive known (but not always well-known) facts. We start
with a comparison of the general Lagrangian and Hamiltonian formalism of the
harmonic oscillator and analyze the relation between the canonical momenta and
the velocities (i.e. the first derivatives of the canonical coordinates). We
show that the seemingly non-symplectic transfer maps at entrance and exit of
solenoid magnets can be re-interpreted as transformations between the canonical
and the mechanical momentum, which differ by the vector potential.
In a second step we rederive the transfer matrix for charged particle motion
in bending magnets from the Lorentz force equation in cartesic coordinates. We
rediscover the geometrical and physical meaning of the local curvilinear
coordinate system. We show that analog to the case of solenoids - also the
transfer matrix of bending magnets can be interpreted as a symplectic product
of 3 non-symplectic matrices, where the entrance and exit matrices are
transformations between local cartesic and curvilinear coordinate systems.
We show that these matrices are required to compare the second moment
matrices of distributions obtained by numerical tracking in cartesic
coordinates with those that are derived by the transfer a matrix method.Comment: 7 pages, 2 figure
California Health Care Market Report 2005
Examines relationships among providers, physicians, hospitals, and patients, differences in the way physicians and hospitals organize, and factors that have prompted hospitals, medical groups, and health plans to redefine their relationships
Israel\u27s Transboundary Water Disputes
As water is necessary to the function of life, it is imperative to understand the role of water in the politically turbulent Middle East. This paper will focus on Israel’s water disputes with her neighbors and how such disputes have either led to military confrontation, have been partially resolved, and otherwise continue to exist. As populations in the region are expected to increase, the need for water, already in short supply, will be magnified. Thus negotiations to settle water disputes and provide for equitable distribution of the water resources will become more contentious. This legal analysis of Israel’s water disputes will hopefully provide some guidance to the settlement of such issues in Israel’s future peace negotiations with the Syrians and Palestinians
A general constitutive model for dense, fine particle suspensions validated in many geometries
Fine particle suspensions (such as cornstarch mixed with water) exhibit
dramatic changes in viscosity when sheared, producing fascinating behaviors
that captivate children and rheologists alike. Recent examination of these
mixtures in simple flow geometries suggests inter-granular repulsion is central
to this effect --- for mixtures at rest or shearing slowly, repulsion prevents
frictional contacts from forming between particles, whereas, when sheared more
forcefully, granular stresses overcome the repulsion allowing particles to
interact frictionally and form microscopic structures that resist flow.
Previous constitutive studies of these mixtures have focused on particular
cases, typically limited to two-dimensional, steady, simple shearing flows. In
this work, we introduce a predictive and general, three-dimensional continuum
model for this material, using mixture theory to couple the fluid and particle
phases. Playing a central role in the model, we introduce a micro-structural
state variable, whose evolution is deduced from small-scale physical arguments
and checked with existing data. Our space- and time-dependent model is
implemented numerically in a variety of unsteady, non-uniform flow
configurations where it is shown to accurately capture a variety of key
behaviors: (i) the continuous shear thickening (CST) and discontinuous shear
thickening (DST) behavior observed in steady flows, (ii) the time-dependent
propagation of `shear jamming fronts', (iii) the time-dependent propagation of
`impact activated jamming fronts', and (iv) the non-Newtonian, `running on
oobleck' effect wherein fast locomotors stay afloat while slow ones sink
Persistence of fractional Brownian motion with moving boundaries and applications
We consider various problems related to the persistence probability of
fractional Brownian motion (FBM), which is the probability that the FBM
stays below a certain level until time . Recently, Oshanin et al. study a
physical model where persistence properties of FBM are shown to be related to
scaling properties of a quantity , called steady-state current. It turns
out that for this analysis it is important to determine persistence
probabilities of FBM with a moving boundary. We show that one can add a
boundary of logarithmic order to a FBM without changing the polynomial rate of
decay of the corresponding persistence probability which proves a result needed
in Oshanin et al. Moreover, we complement their findings by considering the
continuous-time version of . Finally, we use the results for moving
boundaries in order to improve estimates by Molchan concerning the persistence
properties of other quantities of interest, such as the time when a FBM reaches
its maximum on the time interval or the last zero in the interval
.Comment: 13 page
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