arXiv subjects

Mischa Panchenko

Publications and source records attributed to Mischa Panchenko.

5 recordsLinked to original sources

arXiv2017

The infrared triangle in the context of IR safe S matrices

In the present note we show that the recently established connections between soft theorems, large gauge transformations and memories are persistant in the infrared safe formulation of quantum field theory. They take a different and simplified form and can all be derived from the non-trivial asymptotic dynamics that is proper to any theory with massless fields. Several results in this paper had already been presented in one form or another with varying interpretations. The new parts here are an improved derivation of charges for large gauge transformations in the framework of non-trivial asymptotic dynamics, the connection to the classical memory effect and an overall more unified and accessible treatment of the topic. Since the formulation of QFT without infrared divergences is physically more appealing, the infrared safe version of the above connections should be so as well.

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arXiv2016

Asymptotic dynamics, large gauge transformations and infrared symmetries

Infrared divergences in QED and other theories with massless particles show that in such theories the $S$ matrix cannot be defined in the usual way. Typically, this is not viewed as a big problem since one is interested in cross sections, in which the divergences cancel. Recently, one particular type of divergences known as soft theorems was connected to a symmetry principle - the antipodal matching of large gauge transformations. However, there is a way to define an IR finite $S$ matrix in QED and similar theories by dropping the assumption of trivial asymptotic dynamics. In the present paper we investigate the role of soft theorems and invariance under large gauge transformations in the context of the finite $S$ matrix. Before doing so, the construction of asymptotic dynamics is reviewed and extended. The key results are that subleading soft factors can be included in a natural way in the asymptotic dynamics. Once this is done, soft modes decouple from the IR finite $S$ matrix and this decoupling, which can be understood as a spontaneously broken symmetry, is equivalent to the invariance under large gauge transformations (or in other words to the antipodal matching). To show this equivalence a special property for field operators at null infinity, i.e. for the program of asymptotic quantization, is assumed. Finally, we speculate about the modification of the decoupling of soft modes in the presence of black holes.

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arXiv2016

Black Hole Based Quantum Computing in Labs and in the Sky

Analyzing some well established facts, we give a model-independent parameterization of black hole quantum computing in terms of a set of macro and micro quantities and their relations. These include the relations between the extraordinarily-small energy gap of black hole qubits and important time-scales of information-processing, such as, scrambling time and Page's time. We then show, confirming and extending previous results, that other systems of nature with identical quantum informatics features are attractive Bose-Einstein systems at the critical point of quantum phase transition. Here we establish a complete isomorphy between the quantum computational properties of these two systems. In particular, we show that the quantum hair of a critical condensate is strikingly similar to the quantum hair of a black hole. Irrespectively whether one takes the similarity between the two systems as a remarkable coincidence or as a sign of a deeper underlying connection, the following is evident. Black holes are not unique in their way of quantum information processing and we can manufacture black hole based quantum computers in labs by taking advantage of quantum criticality.

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arXiv2015

The Lieb-Liniger model at the critical point as toy model for Black Holes

In a previous series of papers it was proposed that black holes can be understood as Bose-Einstein condensates at the critical point of a quantum phase transition. Therefore other bosonic systems with quantum criticalities, such as the Lieb-Liniger model with attractive interactions, could possibly be used as toy models for black holes. Even such simple models are hard to analyse, as mean field theory usually breaks down at the critical point. Very few analytic results are known. In this paper we present a method of studying such systems at quantum critical points analytically. We will be able to find explicit expressions for the low energy spectrum of the Lieb-Liniger model and thereby to confirm the expected black hole like properties of such systems. This opens up an exciting possibility of constructing and studying black hole like systems in the laboratory.

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arXiv2015

Black Hole Type Quantum Computing in Critical Bose-Einstein Systems

Recent ideas about understanding physics of black hole information-processing in terms of quantum criticality allow us to implement black hole mechanisms of quantum computing within critical Bose-Einstein systems. The generic feature, uncovered both by analytic and numeric studies, is the emergence at the critical point of gapless weakly-interacting modes, which act as qubits for information-storage at a very low energy cost. These modes can be effectively described in terms of either Bogoliubov or Goldstone degrees of freedom. The ground-state at the critical point is maximally entangled and far from being classical. We confirm this near-critical behavior by a new analytic method. We compute growth of entanglement and show its consistency with black hole type behavior. On the other hand, in the over-critical regime the system develops a Lyapunov exponent and scrambles quantum information very fast. By, manipulating the system parameters externally, we can put it in and out of various regimes and in this way control the sequence of information storage and processing. By using gapless Bogoliubov modes as control qubits we design some simple logic gates.

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