Sunday, November 9, 2014

gmma volatility σ is different for every observer. However, what we will call volatility-time σ

[PDF]Space-time Finance - Espen Haug
www.espenhaug.com/SpaceTimeFLong.pdf 翻譯這個網頁
The Relativity Theory's Implications for Mathematical Finance ... Relativity, relativistic volatility, invariant uncertainty-time, from world economy to universe economy, stochastic velocity dependent volatility. 1 Introduction ...... dose of gamma rays.
 
Space-Time Interval 
Consider two events that are close together in space-time.  Just as we can compute the distance between two points in space, dl, we can also compute the distance between two nearby events in space-time The important fact about the space-time distance, called the space-time interval, is that it is invariant; that is, it is measured to be the same by all observers and its value does not depend on how we choose to label the events.

The space-time interval ds is defined by

    ds2 = -(cdt)2 + dl2
where c is the speed of light and dt is the difference between the time labels at the two nearby events.

The difference dt is called the coordinate time difference to remind us of the fact that its value depends on how we choose to label the events, in contrast to the interval ds which does not. 

Notice something peculiar about the interval. Its square can be positive, zero or negative! 
If ds2 < 0 the two nearby events are said to separated by a time-like interval

If ds2> 0 the two nearby events are said to be separated by a space-like interval If ds2 = 0 the two events are said to be separated by a light-like interval

    Proper Time and Proper Distance

Consider a space-time interval with dl = 0. In this case
    ds2 = -(cdt)2
What does this mean? This means that the two nearby events are actually at the same spatial point, but are separated in time by an amount dt.

The time measured at any given point is called the proper time.  The difference dt is the proper time that has elapsed between the two events. It is the time measured by a clock at that point. 
The elapsed proper time is just |ds2|1/2/c
Now consider setting dt = 0. In this case
    ds2 = dl2
This shows that when two events have the same time, that is, when they are simultaneous the spatial distance between them is invariant, that is, measured to be the same by all observers. This distance is called the proper distance between the two points. What about the proper time of observers who are moving relative to the coordinate system?  How do we compute their proper times? Let's start with the formula for the space-time interval
    (a) ds2 = -(cdt)2 + dl2
After a little bit of algebra we get 
    dt = |ds2|1/2/c = dt[1  - (v/c)2]1/2.
The following 
dt = |ds2|1/2/c is the expression for the proper time difference not only for observers at rest in the coordinate system but for all observers, however they move,  
provided that they move only along time-like world-lines. 

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