21,202 research outputs found
Explicit solutions for relativistic acceleration and rotation
The Lorentz transformations are represented by Einstein velocity addition on
the ball of relativistically admissible velocities. This representation is by
projective maps. The Lie algebra of this representation defines the
relativistic dynamic equation. If we introduce a new dynamic variable, called
symmetric velocity, the above representation becomes a representation by
conformal, instead of projective maps. In this variable, the relativistic
dynamic equation for systems with an invariant plane, becomes a non-linear
analytic equation in one complex variable. We obtain explicit solutions for the
motion of a charge in uniform, mutually perpendicular electric and magnetic
fields. By assuming the Clock Hypothesis and using these solutions, we are able
to describe the space-time transformations between two uniformly accelerated
and rotating systems.Comment: 15 pages 1 figur
A new view on relativity: Part 2. Relativistic dynamics
The Lorentz transformations are represented on the ball of relativistically
admissible velocities by Einstein velocity addition and rotations. This
representation is by projective maps. The relativistic dynamic equation can be
derived by introducing a new principle which is analogous to the Einstein's
Equivalence Principle, but can be applied for any force. By this principle, the
relativistic dynamic equation is defined by an element of the Lie algebra of
the above representation. If we introduce a new dynamic variable, called
symmetric velocity, the above representation becomes a representation by
conformal, instead of projective maps. In this variable, the relativistic
dynamic equation for systems with an invariant plane, becomes a non-linear
analytic equation in one complex variable. We obtain explicit solutions for the
motion of a charge in uniform, mutually perpendicular electric and magnetic
fields. By the above principle, we show that the relativistic dynamic equation
for the four-velocity leads to an analog of the electromagnetic tensor. This
indicates that force in special relativity is described by a differential
two-form
Jewish Revenge: Haredi Action in the Zionist Sphere
This is a pre-copyedited version of an article accepted for publication in (journal title, volume and issue numbers, and year) following peer review. The definitive publisher-authenticated version is available from Wayne State University Press.Jewish ultra-Orthodox (Haredi) cinema in Israel has become increasingly prominent in recent years. Emerging as a highly controversial, secluded, and gender-segregated form of “amateur cinema,” it is currently seeing gradual professionalization. This article discusses Haredi cinema in the context of the Haredi community’s relationship with the Israeli state and the doctrine of Zionism. Appropriating generic conventions of mainstream Hollywood cinema, yet keeping within the secluded Haredi space, this form of minority cinema functions as an alternative (virtual) sphere in which a complex set of negotiations occurs between Jewish ultra-Orthodox ideals and those of the surrounding Israeli society and Zionism. It is reflective of and engaged in the production of recent social and discursive transformations within the Haredi community in Israel. We examine this phenomenon through a focused analysis of the male action genre, specifically the popular series Jewish Revenge (Yehuda Grovais, 2000–2010). As we demonstrate, the mode of representation and the narratives of these films bring models of masculinities and notions of heroism under scrutiny. The Zionist narrative, the national body, and the (imaginary) place of the Haredi within it are being reconfigured through the prism of body politics and fantasies of transgression
The scalar complex potential and the Aharonov-Bohm effect
The Aharonov-Bohm effect is traditionally attributed to the effect of the
electromagnetic 4-potential , even in regions where both the electric field
and the magnetic field are zero. The AB effect
reveals that multiple-valued functions play a crucial role in the description
of an electromagnetic field. We argue that the quantity measured by AB
experiments is a difference in values of a multiple-valued complex function,
which we call a complex potential or {pre-potential. We show that any
electromagnetic field can be described by this pre-potential, and give an
explicit expression for the electromagnetic field tensor through this
potential. The pre-potential is a modification of the two scalar potential
functions.Comment: 10 pages 2 figure
Covariant Uniform Acceleration
We show that standard Relativistic Dynamics Equation F=dp/d\tau is only
partially covariant. To achieve full Lorentz covariance, we replace the
four-force F by a rank 2 antisymmetric tensor acting on the four-velocity. By
taking this tensor to be constant, we obtain a covariant definition of
uniformly accelerated motion. We compute explicit solutions for uniformly
accelerated motion which are divided into four types: null, linear, rotational,
and general. For null acceleration, the worldline is cubic in the time. Linear
acceleration covariantly extends 1D hyperbolic motion, while rotational
acceleration covariantly extends pure rotational motion.
We use Generalized Fermi-Walker transport to construct a uniformly
accelerated family of inertial frames which are instantaneously comoving to a
uniformly accelerated observer. We explain the connection between our approach
and that of Mashhoon. We show that our solutions of uniformly accelerated
motion have constant acceleration in the comoving frame. Assuming the Weak
Hypothesis of Locality, we obtain local spacetime transformations from a
uniformly accelerated frame K' to an inertial frame K. The spacetime
transformations between two uniformly accelerated frames with the same
acceleration are Lorentz. We compute the metric at an arbitrary point of a
uniformly accelerated frame.
We obtain velocity and acceleration transformations from a uniformly
accelerated system K' to an inertial frame K. We derive the general formula for
the time dilation between accelerated clocks. We obtain a formula for the
angular velocity of a uniformly accelerated object. Every rest point of K' is
uniformly accelerated, and its acceleration is a function of the observer's
acceleration and its position. We obtain an interpretation of the
Lorentz-Abraham-Dirac equation as an acceleration transformation from K' to K.Comment: 36 page
Modeling Belief in Dynamic Systems, Part II: Revision and Update
The study of belief change has been an active area in philosophy and AI. In
recent years two special cases of belief change, belief revision and belief
update, have been studied in detail. In a companion paper (Friedman & Halpern,
1997), we introduce a new framework to model belief change. This framework
combines temporal and epistemic modalities with a notion of plausibility,
allowing us to examine the change of beliefs over time. In this paper, we show
how belief revision and belief update can be captured in our framework. This
allows us to compare the assumptions made by each method, and to better
understand the principles underlying them. In particular, it shows that Katsuno
and Mendelzon's notion of belief update (Katsuno & Mendelzon, 1991a) depends on
several strong assumptions that may limit its applicability in artificial
intelligence. Finally, our analysis allow us to identify a notion of minimal
change that underlies a broad range of belief change operations including
revision and update.Comment: See http://www.jair.org/ for other files accompanying this articl
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