506 research outputs found
A Test of CPT Symmetry in K^0 vs \bar{K}^0 to \pi^+\pi^-\pi^0 Decays
I show that the CP-violating asymmetry in K^0 vs \bar{K}^0 \to
\pi^+\pi^-\pi^0 decays differs from that in K_L \to \pi^+\pi^-, K_L \to
\pi^0\pi^0 or the semileptonic K_L transitions, if there exists CPT violation
in K^0-\bar{K}^0 mixing. A delicate measurement of this difference at a super
flavor factory (e.g., the \phi factory) will provide us with a robust test of
CPT symmetry in the neutral kaon system.Comment: 4 pages, 1 figure. To appear in the Proceedings of the International
PHIPSI09 Workshop, October 2009, Beijing, Chin
Measured quantum probability distribution functions for Brownian motion
The quantum analog of the joint probability distributions describing a
classical stochastic process is introduced. A prescription is given for
constructing the quantum distribution associated with a sequence of
measurements. For the case of quantum Brownian motion this prescription is
illustrated with a number of explicit examples. In particular it is shown how
the prescription can be extended in the form of a general formula for the
Wigner function of a Brownian particle entangled with a heat bath.Comment: Phys. Rev. A, in pres
Vacuum Polarization and the Electric Charge of the Positron
We show that higher-order vacuum polarization would contribute a measureable
net charge to atoms, if the charges of electrons and positrons do not balance
precisely. We obtain the limit for the sum of
the charges of electron and positron. This also constitutes a new bound on
certain violations of PCT invariance.Comment: 9 pages, 1 figure attached as PostScript file, DUKE-TH-92-38. Revised
versio
Towards an Axiomatic Formulation of Noncommutative Quantum Field Theory
We propose new Wightman functions as vacuum expectation values of products of
field operators in the noncommutative space-time. These Wightman functions
involve the -product among the fields, compatible with the twisted
Poincar\'e symmetry of the noncommutative quantum field theory (NC QFT). In the
case of only space-space noncommutativity (), we prove the CPT
theorem using the noncommutative form of the Wightman functions. We also show
that the spin-statistics theorem, demonstrated for the simplest case of a
scalar field, holds in NC QFT within this formalism.Comment: 16 pages, version to appear in J. Math. Phy
Pressure Induced Charge Disproportionation in LaMnO
We present a total energy study as a function of volume in the cubic phase of
LaMnO. A charge disproportionated state into planes of
MnO/MnO was found. It is argued that the pressure
driven localisation/delocalisation transition might go smoothly through a
region of Mn and Mn coexistence.Comment: 3 pages, 1 figure, Conference Proceedings: Nanospintronics: Design
and Realization (Kyoto, Japan 24-28 May, 2004
Coherence of a Josephson phase qubit under partial-collapse measurement
We discuss quantum evolution of a decaying state in relation to a recent
experiment of Katz et al. Based on exact analytical and numerical solutions of
a simple model, we identify a regime where qubit retains coherence over a
finite time interval independently of the rates of three competing decoherence
processes. In this regime, the quantum decay process can be continuously
monitored via a ``weak'' measurement without affecting the qubit coherence.Comment: 4p., 2eps figure
Derivation of the quantum probability law from minimal non-demolition measurement
One more derivation of the quantum probability rule is presented in order to
shed more light on the versatile aspects of this fundamental law. It is shown
that the change of state in minimal quantum non-demolition measurement, also
known as ideal measurement, implies the probability law in a simple way.
Namely, the very requirement of minimal change of state, put in proper
mathematical form, gives the well known Lueders formula, which contains the
probability rule.Comment: 8 page
Different Types of Conditional Expectation and the Lueders - von Neumann Quantum Measurement
In operator algebra theory, a conditional expectation is usually assumed to
be a projection map onto a sub-algebra. In the paper, a further type of
conditional expectation and an extension of the Lueders - von Neumann
measurement to observables with continuous spectra are considered; both are
defined for a single operator and become a projection map only if they exist
for all operators. Criteria for the existence of the different types of
conditional expectation and of the extension of the Lueders - von Neumann
measurement are presented, and the question whether they coincide is studied.
All this is done in the general framework of Jordan operator algebras. The
examples considered include the type I and type II operator algebras, the
standard Hilbert space model of quantum mechanics, and a no-go result
concerning the conditional expectation of observables that satisfy the
canonical commutator relation.Comment: 10 pages, the original publication is available at
http://www.springerlink.co
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