arXiv subjects

Zheng Ze Ma

Publications and source records attributed to Zheng Ze Ma.

10 recordsLinked to original sources

arXiv2009

Hawking temperature of Kerr-Newman-AdS black hole from tunneling

Using the null-geodesic tunneling method of Parikh and Wilczek, we derive the Hawking temperature of a general four-dimensional rotating black hole. In order to eliminate the motion of $ϕ$ degree of freedom of a tunneling particle, we have chosen a reference system that is co-rotating with the black hole horizon. Then we give the explicit result for the Hawking temperature of the Kerr-Newman-AdS black hole from the tunneling approach.

hep-th↗

arXiv2008

Hawking Radiation of Black p-Branes from Gravitational Anomaly

We investigate the Hawking radiation of black $p$-branes of superstring theories using the method of anomaly cancelation, specially, we use the method of [S. Iso, H. Umetsu and F. Wilczek, {\sl Phys. Rev. Lett.} {\bf 96}, 151302 (2006); {\sl Phys. Rev. D} {\bf 74}, 044017 (2006)]. The metrics of black $p$-branes are spherically symmetric, but not the Schwarzschild type. In order to simplify the calculation, we first make a coordinate transformation to transform the metric to the Schwarzschild type. Then we calculate its energy-momentum flux from the method of anomaly cancelation of the above mentioned references. The obtained energy-momentum flux is equal to a black body radiation, the thermodynamic temperature of the radiation is equal to its Hawking temperature. And we find that the results are not changed for the original non-Schwarzschild type spherically symmetric metric.

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arXiv2007

Energy-momentum non-conservation on noncommutative spacetime and the existence of infinite spacetime dimension

From the constructions of the quantum spacetime, a four dimensional quantized spacetime can be embedded in a five dimensional continuous spacetime. Thus to observe from the five dimensional continuous spacetime where the four dimensional quantized spacetime is embedded, there exist the energy-momentum flows between the five dimensional continuous spacetime and the four dimensional quantized spacetime. This makes the energy-momentum not locally conserved generally on the four dimensional quantized spacetime. We propose that energy-momentum tensors of noncommutative field theories constructed from the Noether approach are just the correct forms for the energy-momentum tensors of noncommutative field theories. The non-vanishing of the total divergences of the energy-momentum tensors of noncommutative field theories just reflect that energy-momentum are not locally conserved on noncommutative spacetime. At the same time, from the constructions of the quantum spacetime, we propose that the total spacetime dimension of the quantum spacetime is infinite.

hep-th↗

arXiv2007

Microcausality violation of scalar field on noncommutative spacetime with the time-space noncommutativity

Quantum field theories on noncommutative spacetime have many different properties from those on commutative spacetime. In this paper, we study the microcausality of free scalar field on noncommutative spacetime. We expand the scalar field in the form of usual Lorentz invariant measure in noncommutative spacetime. Then we calculate the expectation values of the Moyal commutators for the quadratic operators, such as $ϕ(x)\starϕ(x)$, $π({\bf x},t)\starπ({\bf x},t)$, $\partial_{i}ϕ({\bf x},t)\star\partial_{i}ϕ({\bf x},t)$, and $\partial_{i}ϕ({\bf x},t)\starπ({\bf x},t)$. We obtain that for space-space noncommutativity, i.e., $θ^{0i}=0$ in $θ^{μν}$, microcausality of free scalar field on noncommutative spacetime is satisfied. For time-space noncommutativity, i.e., $θ^{0i}\neq0$ in $θ^{μν}$, microcausality of free scalar field on noncommutative spacetime is violated.

hep-th↗

arXiv2006

The Bekenstein-Hawking Entropy of Higher-Dimensional Rotating Black Holes

A black hole can be regarded as a thermodynamic system described by a grand canonical ensemble. In this paper, we study the Bekenstein-Hawking entropy of higher-dimensional rotating black holes using the Euclidean path-integral method of Gibbons and Hawking. We give a general proof demonstrating that ignoring quantum corrections, the Bekenstein-Hawking entropy is equal to one-fourth of its horizon area for general higher-dimensional rotating black holes.

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arXiv2006

Microcausality of Dirac field on noncommutative spacetime

We study the microcausality of free Dirac field on noncommutative spacetime. We calculate the vacuum and non-vacuum state expectation values for the Moyal commutator $[\barψ_α(x)\starψ_β(x),\barψ_ σ(x^{\prime})\starψ_τ(x^{\prime})]_{\star}$ of Dirac field on noncommutative spacetime. We find that they do not vanish for some cases of the indexes for an arbitrary spacelike interval, no matter whether $θ^{0i}=0$ or $θ^{0i}\neq0$. However for the physical observable quantities of Dirac field such as the Lorentz scalar $:\barψ(x)\starψ(x):$ and the current $j^μ(x)=:\barψ(x)γ^μ\starψ(x):$ etc., we find that they still satisfy the microcausality. Therefore microcausality is satisfied for Dirac field on noncommutative spacetime.

hep-th↗

arXiv2006

Quantum motion equation and Poincare translation invariance of noncommutative field theory

We study the Moyal commutators and their expectation values between vacuum states and non-vacuum states for noncommutative scalar field theory. For noncommutative $ϕ^{\star4}$ scalar field theory, we derive its energy-momentum tensor from translation transformation and Lagrange field equation. We generalize the Heisenberg and quantum motion equations to the form of Moyal star-products for noncommutative $ϕ^{\star4}$ scalar field theory for the case $θ^{0i}=0$ of spacetime noncommutativity. Then we demonstrate the Poincar{\' e} translation invariance for noncommutative $ϕ^{\star4}$ scalar field theory for the case $θ^{0i}=0$ of spacetime noncommutativity.

hep-th↗

arXiv2006

Commutators and propagators of Moyal star-products and microcausality for free scalar field on noncommutative spacetime

We study the Moyal commutators and their expectation values between vacuum states and non-vacuum states for free scalar field on noncommutative spacetime. Then from the Moyal commutators, we find that the microcausality is satisfied for the linear operators of the free scalar field on noncommutative spacetime. We construct the Feynman propagator of Moyal star-product for noncommutative scalar field theory.

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arXiv2006

Anticommutators and propagators of Moyal star-products for Dirac field on noncommutative spacetime

We study the Moyal anticommutators and their expectation values between vacuum states and non-vacuum states for Dirac fields on noncommutative spacetime. Then we construct the propagators of Moyal star-products for Dirac fields on noncommutative spacetime. We find that the propagators of Moyal star-products for Dirac fields are equal to the propagators of Dirac fields on ordinary commutative spacetime.

hep-th↗

arXiv2006

Euler numbers of four-dimensional rotating black holes with the Euclidean signature

For a black hole's spacetime manifold in the Euclidean signature, its metric is positive definite and therefore a Riemannian manifold. It can be regarded as a gravitational instanton and a topological characteristic which is the Euler number is associated. In this paper we derive a formula for the Euler numbers of four-dimensional rotating black holes by the integral of the Euler density on the spacetime manifolds of black holes. Using this formula, we obtain that the Euler numbers of Kerr and Kerr-Newman black holes are 2. We also obtain that the Euler number of the Kerr-Sen metric in the heterotic string theory with one boost angle nonzero is 2 that is in accordence with its topology.

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