We discuss a general method of revealing both space-space and space-time noncommuting structures in various models in particle mechanics exhibiting reparametrisation symmetry. Starting from the commuting algebra in the conventional gauge, it is possible to obtain a noncommuting algebra in a nonstandard gauge. The change of variables relating the algebra in the two gauges is systematically deriv...

this paper extends the scope of algebraic computation based on a non standard × to the more basic case of a non standard +, where standard means associative and commutative. two physically meaningful examples of a non standard + are provided by the observation of motion in special relativity, from either outside (3d) or inside (2d or more), we revisit the “gyro”-theory of ungar to present the m...

With the help of the Seiberg-Witten map, one can obtain an effective action of a deformed QED from a noncommutative QED. Starting from the deformed QED, we investigate the propagation of photons in the background of electromagnetic field, up to the leading order of the noncommutativity parameter. In our setting (both the electric and magnetic fields are parallel to the coordinate axis x and the...

Compacti cation of Matrix Model on a Noncommutative torus is obtained from strings ending on D-branes with background B eld. The BPS spectrum of the system and a novel SL(2; Z) symmetry are discussed. Noncommutativity of space-time coordinates emerged in string theory recently in the context of coincident Dbranes [1]; in fact the embedding coordinates of D-branes turned out to be noncommutative...

We find Lorentzian solutions of spacetime noncommutative gauge theories that are localized exponentially in space and time. Together with time translational invariance of the theories, we argue that perurbative S matrix formulation of such theories is problematic in the sense that the S matrix based on free in and out states misses the spacetime localized degrees. We show that, in 3+1 dimension...

A toy model based upon the q-deformation description for studying the radiation spectrum of black hole is proposed. The starting point is to try to consider the spacetime noncommutativity and to realize it by using a qdeformation algebraic technique. We calculated the radiation spectrum of Schwarzschild black hole in this framework. The new distribution deviates from the standard thermal spectr...

We analyze the microcausality of free scalar field on noncommutative spacetime. To adopt the usual Lorentz invariant spectral measure, through the result of the expectation values of the Moyal commutators, for the quadratic operators such as φ(x) ⋆ φ(x), π(x, t) ⋆ π(x, t), ∂iφ(x, t) ⋆ ∂iφ(x, t), and ∂iφ(x, t) ⋆ π(x, t), we obtain that for the case θ = 0 of the spacetime noncommutativity, the mi...