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Time's arrow in B mesons

Nature 491, 640 (29 November 2012)

A cornerstone of theoretical particle physics — the idea that not all processes run in the same way forwards in time as they do backwards — has been observed directly for the first time.

Members of the BaBar Collaboration trawled data from their experiment (pictured), which ran at the SLAC National Accelerator Laboratory…

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Leonard Susskind

Stanford Institute for Theoretical Physics and Department of Physics, Stanford

University

Stanford, CA 94305-4060, USA

Abstract

This is the written version of a lecture at the KITP workshop on Bits, Branes and Black Holes. In it I describe work with D. Harlow, S. Shenker, D. Stanford which explains how the tree-like structure of eternal ination, together with the existence of terminal vacua, leads to an arrow-of-time. Conformal symmetry of the dS/CFT type is inconsistent with an arrow-of-time and must be broken. The presence in the landscape of terminal vacua leads to a new kind of attractor called a fractal - which both breaks conformal symmetry, and creates a directional time-asymmetry.

This can be seen from both the local or causal-patch viewpoint, and also from the global or multiversal viewpoint. The resulting picture is consistent with the view recently expressed by Bousso.

In the last part of the lecture I illustrate how the tree-model can be useful in explaining the value of the cosmological constant, and the cosmic coincidence problem.

The mechanisms are not new but the description is.

Figure 5: On the right side of the figure a red bubble is shown nucleating in de Sitter space.

Ignoring later nucleations, the bubble expands to fill the causal future of the nucleation point. The tree-analog of the same process is shown in the left side of the figure.

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Time’s Arrow for Shockwaves ; Bit-Reversible Lyapunov and “Covariant” Vectors ; Symmetry Breaking

Wm. G. Hoover and Carol G. Hoover

Ruby Valley Research Institute

Highway Contract 60, Box 601

Ruby Valley, Nevada 89833

(Dated: November 13, 2012)

Abstract

Strong shockwaves generate entropy quickly and locally. The Newton-Hamilton equations of motion, which underly the dynamics, are perfectly time-reversible. How do they generate the irreversible shock entropy? What are the symptoms of this irreversibility? We investigate these questions using Levesque and Verlet’s bit-reversible algorithm. In this way we can generate an entirely imaginary past consistent with the irreversibility observed in the present. We use Runge-Kutta integration to analyze the local Lyapunov instability of nearby “satellite” trajectories. From the forward and backward processes we identify those particles most intimately connected with the irreversibility described by the Second Law of Thermodynamics. Despite the perfect time symmetry of the particle trajectories, the fully-converged vectors associated with the largest Lyapunov exponents, forward and backward in time, are qualitatively different. The vectors display a time-symmetry breaking equivalent to Time’s Arrow. That is, in autonomous Hamiltonian shockwaves the largest local Lyapunov exponents, forward and backward in time, are quite different.

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lunedì 1 ottobre 2012