No Arabic abstract
Quadratic polynomially deformed $su(1,1)$ and $su(2)$ algebras are utilised in model Hamiltonians to show how the gravitational system consisting of a black hole, infalling radiation and outgoing (Hawking) radiation can be solved exactly. The models allow us to study the long-time behaviour of the black hole and its outgoing modes. In particular, we calculate the bipartite entanglement entropies of subsystems consisting of a) infalling plus outgoing modes and b) black hole modes plus the infalling modes,using the Janus-faced nature of the model.The long-time behaviour also gives us glimpses of modifications in the character of Hawking radiation. Lastly, we study the phenomenon of superradiance in our model in analogy with atomic Dicke superradiance.
The effect of the Hawking temperature on the entanglement and teleportation for the scalar field in a most general, static and asymptotically flat black hole with spherical symmetry has been investigated. It is shown that the same initial entanglement for the state parameter $alpha$ and its normalized partners $sqrt{1-alpha^{2}}$ will be degraded by the Hawking effect with increasing Hawking temperature along two different trajectories except for the maximally entangled state. In the infinite Hawking temperature limit, corresponding to the case of the black hole evaporating completely, the state has no longer distillable entanglement for any $alpha$. It is interesting to note that the mutual information in this limit equals to just half of the initially mutual information. It has also been demonstrated that the fidelity of teleportation decreases as the Hawking temperature increases, which just indicates the degradation of entanglement.
We propose that the Hawking radiation energy and entropy flow rates from a black hole can be viewed as a one-dimensional (1D), non-equilibrium Landauer transport process. Support for this viewpoint comes from previous calculations invoking conformal symmetry in the near-horizon region, which give radiation rates that are identical to those of a single 1D quantum channel connected to a thermal reservoir at the Hawking temperature. The Landauer approach shows in a direct way the particle statistics independence of the energy and entropy fluxes of a black hole radiating into vacuum, as well as one near thermal equilibrium with its environment. As an application of the Landauer approach, we show that Hawking radiation gives a net entropy production that is 50% larger than that obtained assuming standard three-dimensional emission into vacuum.
We derive the Hawking radiation spectrum of anyons, namely particles in (2+1)-dimension obeying fractional statistics, from a BTZ black hole, in the tunneling formalism. We examine ways of measuring the spectrum in experimentally realizable systems in the laboratory.
In 1974 Steven Hawking showed that black holes emit thermal radiation, which eventually causes them to evaporate. The problem of the fate of information in this process is known as the black hole information paradox. It inspired a plethora of theoretical models which, for the most part, assume either a fundamental loss of information or some form of quantum gravity. At variance to the main trends, a conservative approach assuming information retrieval in quantum correlation between Hawking particles was proposed and recently developed within qubit toy-models. Here we leverage modern quantum information to incarnate this idea in a realistic model of quantised radiation. To this end we employ the formalism of quantum Gaussian states together with the continuous-variables version of the quantum marginal problem. Using a rigorous solution to the latter we show that the thermality of all Hawking particles is consistent with a global pure state of the radiation. Surprisingly, we find out that the radiation of an astrophysical black hole can be thermal until the very last particle. In contrast, the thermality of Hawking radiation originating from a microscopic black hole -- which is expected to evaporate through several quanta -- is not excluded, though there are constraints on modes frequencies. Our result support the conservative resolution to the black hole information paradox. Furthermore, it suggests a systematic programme for probing the global state of Hawking radiation.
We take into account two further physical models which play an utmost importance in the framework of Analogue Gravity. We first consider Bose--Einstein condensates (BEC) and then surface gravity waves in water. Our approach is based on the use of the master equation we introduced in a previous work. A more complete analysis of the singular perturbation problem involved, with particular reference to the behavior in the neighbourhood of the (real) turning point and its connection with the WKB approximation, allows us to verify the thermal character of the particle production process. Furthermore, we can provide a simple scheme apt to calculate explicitly the greybody factors in the case of BEC and surface waves. This corroborates the improved approach we proposed for studying the analogue Hawking effect in the usual limit of small dispersive effects.