16140829
Typicality versus thermality: an analytic distinction
In systems with a large degeneracy of states such as black holes, one expects that the average value of probe correlation functions will be well approximated by the thermal ensemble. To understand how correlation functions in individual microstates differ from the canonical ensemble average and from each other, we study the variances in correlators. Using general statistical considerations, we show that the variance between microstates will be exponentially suppressed in the entropy. However, by exploiting the analytic properties of correlation functions we argue that these variances are amplified in imaginary time, thereby distinguishing pure states from the thermal density matrix. We demonstrate our general results in specific examples and argue that our results apply to the microstates of black holes.
216051678
Entwinement and the emergence of spacetime
A bstractIt is conventional to study the entanglement between spatial regions of a quantum field theory. However, in some systems entanglement can be dominated by “internal”, possibly gauged, degrees of freedom that are not spatially organized, and that can give rise to gaps smaller than the inverse size of the system. In a holographic context, such small gaps are associated to the appearance of horizons and singularities in the dual spacetime. Here, we propose a concept of entwinement, which is intended to capture this fine structure of the wavefunction. Holographically, entwinement probes the entanglement shadow — the region of spacetime not probed by the minimal surfaces that compute spatial entanglement in the dual field theory. We consider the simplest example of this scenario — a 2d conformal field theory (CFT) that is dual to a conical defect in AdS3 space. Following our previous work, we show that spatial entanglement in the CFT reproduces spacetime geometry up to a finite distance from the conical defect. We then show that the interior geometry up to the defect can be reconstructed from entwinement that is sensitive to the discretely gauged, fractionated degrees of freedom of the CFT. Entwinement in the CFT is related to non-minimal geodesics in the conical defect geometry, suggesting a potential quantum information theoretic meaning for these objects in a holographic context. These results may be relevant for the reconstruction of black hole interiors from a dual field theory.
4364283
The entropy of a hole in spacetime
A bstractWe compute the gravitational entropy of “spherical Rindler space”, a timedependent, spherically symmetric generalization of ordinary Rindler space, defined with reference to a family of observers traveling along non-parallel, accelerated trajectories. All these observers are causally disconnected from a spherical region H (a “hole”) located at the origin of Minkowski space. The entropy evaluates to S = $ \mathcal{A} $/4G, where $ \mathcal{A} $ is the area of the spherical acceleration horizon, which coincides with the boundary of H. We propose that S is the entropy of entanglement between quantum gravitational degrees of freedom supporting the interior and the exterior of the sphere H.
118473358
Polarizing bubble collisions
We predict the polarization of cosmic microwave background (CMB) photons that results from a cosmic bubble collision. The polarization is purely E-mode, symmetric around the axis pointing towards the collision bubble, and has several salient features in its radial dependence that can help distinguish it from a more conventional explanation for unusually cold or hot features in the CMB sky. The anomalous ``cold spot'' detected by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite is a candidate for a feature produced by such a collision, and the Planck satellite and other proposed surveys will measure the polarization on it in the near future. The detection of such a collision would provide compelling evidence for the string theory landscape.
118400220
Quantitative approaches to information recovery from black holes
The evaporation of black holes into apparently thermal radiation poses a serious conundrum for theoretical physics: at face value, it appears that in the presence of a black hole, quantum evolution is non-unitary and destroys information. This information loss paradox has its seed in the presence of a horizon causally separating the interior and asymptotic regions in a black hole spacetime. A quantitative resolution of the paradox could take several forms: (a) a precise argument that the underlying quantum theory is unitary, and that information loss must be an artifact of approximations in the derivation of black hole evaporation, (b) an explicit construction showing how information can be recovered by the asymptotic observer, (c) a demonstration that the causal disconnection of the black hole interior from infinity is an artifact of the semiclassical approximation. This review summarizes progress on all these fronts.
15617697
Trace Anomaly in Geometric Discretization
I develop the simplest geometric-discretized analogue of two dimensional scalar field theory, which qualitatively reproduces the trace anomaly of the continuous theory. The discrete analogue provides an interpretation of the trace anomaly in terms of a non-trivial transformation of electric-magnetic duality-invariant modes of resistor networks that accommodate both electric and magnetic charge currents.
7513198
Time scale of the thermal multifragmentation in p(3.6 GeV) + Au collisions
The relative angle correlation of intermediate mass fragments has been studied for p+Au collisions at 3.6 GeV. Strong suppression at small angles is observed caused by IMF-IMF Coulomb repulsion. Experimental correlation function is compared to that obtained by the multi-body Coulomb trajectory calculations with the various decay time of fragmenting system. The combined model including the empirically modified intranuclear cascade followed by statistical multifragmentation was used to generate starting conditions for these calculations. The model dependence of the results obtained has been carefully checked. The mean decay time of fragmenting system is found to be 85 +- 50 fm/c.
18167299
N/Z DEPENDENCE OF PROJECTILE FRAGMENTATION
The N/Z dependence of projectile fragmentation at relativistic energies has been studied in a recent experiment at the GSI laboratory with the ALADiN forward spectrometer coupled to the LAND neutron detector. Besides a primary beam of 124Sn, also secondary beams of 124La and 107Sn delivered by the FRS fragment separator have been used in order to extend the range of isotopic compositions of the produced spectator sources. With the achieved mass resolution of ΔA/A ≈ 1.5%, lighter isotopes with atomic numbers Z ≤ 10 are individually resolved. The presently ongoing analyses of the measured isotope yields focus on isoscaling and its relation to the properties of hot fragments at freeze-out and on the derivation of chemical freeze-out temperatures which are found to be independent of the isotopic composition of the studied systems. The latter result is at variance with the predictions for limiting temperatures as obtained with finite-temperature Hartree-Fock calculations.
109634219
Heavy-ion test of detectors with conventional and resistive Micromegas used in TPC configuration
Abstract We have performed tests of Micromegas detector prototypes using the heavy-ion beams from the SIS synchrotron of GSI (Darmstadt, Germany). The beams varied from C 6 + 12 to Au 65 + 179 and from 250 to 1000 MeV per nucleon. We have tested two amplification technologies, conventional and resistive Micromegas, and two construction concepts, bulk-Micromegas and micro-meshes screwed on the PCB. The obtained position resolution below 200 μ m for 5 mm wide strips implies that the bulk resistive Micromegas technology might meet the requirements of the future R3B TPC project. We also developed a fast and very low noise front-end electronics connected directly to the Printed Circuit Board (PCB) of the detector itself. This concept has shown very good performances and robustness.
16807669
Nuclear multifragmentation and fission: Similarity and differences
Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid–fog phase transition inside the spinodal region. The experimental data for p(8.1GeV)+Au collisions are analyzed. It is concluded that the decay process of hot nuclei is characterized by two size parameters: one density at the transition state and one at the kinetic freeze-out. The similarity between the dynamics of fragmentation and ordinary fission is discussed. The IMF emission time is related to the mean rupture time at the multiscission point, which corresponds to the kinetic freeze-out configuration.
59570123
KRATTA, a versatile triple telescope array for charged reaction products
Abstract A new detection system KRATTA, Krakow Triple Telescope Array, is presented. This versatile, low threshold, broad energy range system has been built to measure the energy, emission angle, and isotopic composition of light charged reaction products. It consists of 38 independent modules which can be arranged in an arbitrary configuration. A single module, covering actively about 4.5 msr of the solid angle at the optimal distance of 40 cm from the target, consists of three identical, 500 μ m thick, large area photodiodes, used also for direct detection, and of two CsI(1500 ppm Tl) crystals of 2.5 and 12.5 cm length, respectively. All the signals are digitally processed. The lower identification threshold, due to the thickness of the first photodiode, has been reduced to about 2.5 MeV for protons ( ∼ 65 μ m of Si equivalent) by applying a pulse shape analysis. The pulse shape analysis allowed also to decompose the complex signals from the middle photodiode into their ionization and scintillation components and to obtain a satisfactory isotopic resolution with a single readout channel. The upper energy limit for protons is about 260 MeV. The whole setup is easily portable. It performed very well during the ASY-EOS experiment, conducted in May 2011 at GSI. The structure and performance of the array are described using the results of Au+Au collisions at 400 MeV/nucleon obtained in this experiment.