“With a View to Speech”

The Beast & the Sovereign, by Jacques Derrida, 2 volumes, translated by Geoffrey Bennington, edited by Geoffrey Bennington and Peggy Kamuf. The Seminars of Jacques Derrida. Chicago: University of Chicago Press, 2009 and 2011. Volume 1, 349 pp. $22.50 paper,$38.00 cloth. Volume 2, 293 pp. $30.00 e-book,$35.00 cloth

Gamma-Ray Burst without Baryonic and Magnetic Load?

We show that, contrary to common belief, internal shocks can arise in an accelerating radiation-dominated jet if it is confined even weakly to a converging opening angle because the acceleration declines. The radiation-dominated internal shock (RDIS) enables a very efficient yet highly nonthermal emission by Fermi-like photon acceleration, keeping the electron-positron ($e^{\pm}$) pair photosphere and inertia up to a high Lorentz factor >1000. In gamma-ray bursts (GRBs), a weak confinement would persist beyond the progenitor star or surrounding matter because of the fast cocoon accompanying the breakout jet. The simplest model predicts few high-energy cosmic rays and neutrinos, and a correlation between the early afterglow and the GeV-TeV prompt emission. The central engine allows a less fine-tuned baryon load than previously thought, even including pure-leptonic unmagnetized outflows.Comment: 10 pages, 3 figures, final version to be published in Progress of Theoretical Physic

Hydrodynamical effects in internal shock of relativistic outflows

We study both analytically and numerically hydrodynamical effects of two colliding shells, the simplified models of the internal shock in various relativistic outflows such as gamma-ray bursts and blazars. We pay particular attention to three interesting cases: a pair of shells with the same rest mass density (``{\it equal rest mass density}''), a pair of shells with the same rest mass (``{\it equal mass}''), and a pair of shells with the same bulk kinetic energy (``{\it equal energy}'') measured in the intersteller medium (ISM) frame. We find that the density profiles are significantly affected by the propagation of rarefaction waves. A split-feature appears at the contact discontinuity of two shells for the ``equal mass'' case, while no significant split appears for the ``equal energy'' and ``equal rest mass density'' cases. The shell spreading with a few ten percent of the speed of light is also shown as a notable aspect caused by rarefaction waves. The conversion efficiency of the bulk kinetic energy to internal one is numerically evaluated. The time evolutions of the efficiency show deviations from the widely-used inellastic two-point-mass-collision model.Comment: 29 pages, 16 figures, accepted by Ap

Deterministic quantum teleportation of photonic quantum bits by a hybrid technique

Quantum teleportation allows for the transfer of arbitrary, in principle, unknown quantum states from a sender to a spatially distant receiver, who share an entangled state and can communicate classically. It is the essence of many sophisticated protocols for quantum communication and computation. In order to realize flying qubits in these schemes, photons are an optimal choice, however, teleporting a photonic qubit has been limited due to experimental inefficiencies and restrictions. Major disadvantages have been the fundamentally probabilistic nature of linear-optics Bell measurements as well as the need for either destroying the teleported qubit or attenuating the input qubit when the detectors do not resolve photon numbers. Here we experimentally realize fully deterministic, unconditional quantum teleportation of photonic qubits. The key element is to make use of a "hybrid" technique: continuous-variable (CV) teleportation of a discrete-variable, photonic qubit. By optimally tuning the receiver's feedforward gain, the CV teleporter acts as a pure loss channel, while the input dual-rail encoded qubit, based on a single photon, represents a quantum error detection code against amplitude damping and hence remains completely intact for most teleportation events. This allows for a faithful qubit transfer even with imperfect CV entangled states: the overall transfer fidelities range from 0.79 to 0.82 for four distinct qubits, all of them exceeding the classical limit of teleportation. Furthermore, even for a relatively low level of the entanglement, qubits are teleported much more efficiently than in previous experiments, albeit post-selectively (taking into account only the qubit subspaces), with a fidelity comparable to the previously reported values

Thermal Radiation from GRB Jets

In this study, the light curves and spectrum of the photospheric thermal radiation from ultrarelativistic gamma-ray burst (GRB) jets are calculated using 2D relativistic hydrodynamic simulations of jets from a collapsar. As the jet advances, the density around the head of the jet decreases, and its Lorentz factor reaches as high as 200 at the photosphere and 400 inside the photosphere. For an on-axis observer, the photosphere appears concave shaped due to the low density and high beaming factor of the jet. The luminosity varies because of the abrupt change in the position of the photosphere due to the internal structure of the jet. Comparing our results with GRB090902B, the flux level of the thermal-like component is similar to our model, although the peak energy looks a little bit higher (but still within a factor of 2). From the comparison, we estimate that the bulk Lorentz factor of GRB090902B is $\Gamma \sim 2.4 \times 10^2 (r/10^{12} \rm cm$) where $r$ is the radius of the photosphere. The spectrum for an on-axis observer is harder than that for an off-axis observer. There is a time lag of a few seconds for high energy bands in the light curve. This may be the reason for the delayed onset of GeV emission seen in GRB080916C. The spectrum below the peak energy is a power law and the index is $2.3 \sim 2.6$ which is softer than that of single temperature plank distribution but still harder than that of typical value of observed one.Comment: 15 pages, 5 figures, revised to Ap