The only point that IMO requires a little more elaboration is the
following (Sebastien and others, feel free to ask us to elaborate on
anything else):
> SO The things Proteus refers to are real physical systems, not symbols.
Bruce, do you think that proteus "acts" on real physical systems?
Consider an infon using data coming from a sensor measuring, say, room
temperature in Proteus. How is it different from some random bytes
used the same sensor fed into a "conventional", say, java process that
is displaying that temperature remotely on my phone - for example.
I think I know the answer, the example with airline ticket on the
website was my ahaha! moment, but for the sake of the reader I'm
asking here anyway.
Thanks,
Davide
The only point that IMO requires a little more elaboration is the
following:
> SO The things Proteus refers to are real physical systems, not symbols.
Bruce, do you think that proteus "acts" on real physical systems?
How cool.
However, I don't get the following:
> In other words, can we say that there is no action
> that moves the system from state 1 to state 3,
> for example? No, because we could either get
> to that state through a combination of actions
> (in which case just put it in), or we can never get
> to it (in which case why list it in the first place?)
What if state 3 can be only reached from state 4 or 2 and not from
state 1? Think of a switch like the one on the right of this picture:
http://media.rsdelivers.cataloguesolutions.com/LargeProductImages/R193573-01.jpg
I see that this is essential to go to the group theory (which I am
familiar with, although not fluent in), so I believe some more
elaboration is needed.
Bye,
;Dav
On Sun, Apr 10, 2011 at 7:05 AM, Davide Del Vento
<davide.d...@gmail.com> wrote:
> However, I don't get the following:
>
>> In other words, can we say that there is no action
>> that moves the system from state 1 to state 3,
>> for example? No, because we could either get
>> to that state through a combination of actions
>> (in which case just put it in), or we can never get
>> to it (in which case why list it in the first place?)
>
> What if state 3 can be only reached from state 4 or 2 and not from
> state 1? Think of a switch like the one on the right of this picture:
> http://media.rsdelivers.cataloguesolutions.com/LargeProductImages/R193573-01.jpg
This is partially a statement about mathematical closure.
Definitionally, if you can't get to state 3 from state 1, then you
don't have a group. In your example, it is possible to reach state 3
from state 1, but you have to traverse through state 2 first. This is
perfectly compatible with group theory (and infon theory).
Bruce's point is that we can't conjure up a system with impossible
states. We can wax poetic about a possible state of affairs, but if
the system can't logically be arranged that way, then we are speaking
nonsense. Consider a Rubik's Cube. If you take two colored stickers
on the corner and swap them, you have a Rubik's Cube that can never be
solved without changing the stickers again. You can rotate it through
as many combinations as you like, but you can't reach a solved state
by working within the defined operations of the system.
However this line of thought raises a separate question for me. When
examining systems in the physical world, we appear to have one-way
operations. If you break a teacup, you can't put it back together.
Entropy is directional, right? How does Proteus address this?
dvd
However, I don't get the following:
> In other words, can we say that there is no action
> that moves the system from state 1 to state 3,
> for example? No, because we could either get
> to that state through a combination of actions
> (in which case just put it in), or we can never get
> to it (in which case why list it in the first place?)
What if state 3 can be only reached from state 4 or 2 and not from
state 1? Think of a switch like the one on the right of this picture:
http://media.rsdelivers.cataloguesolutions.com/LargeProductImages/R193573-01.jpg
In your example, it is possible to reach state 3
from state 1, but you have to traverse through state 2 first. This is
perfectly compatible with group theory (and infon theory).
Bruce's point is that we can't conjure up a system with impossible
states. We can wax poetic about a possible state of affairs, but if
the system can't logically be arranged that way, then we are speaking
nonsense. Consider a Rubik's Cube. If you take two colored stickers
on the corner and swap them, you have a Rubik's Cube that can never be
solved without changing the stickers again. You can rotate it through
as many combinations as you like, but you can't reach a solved state
by working within the defined operations of the system.
However this line of thought raises a separate question for me. When
examining systems in the physical world, we appear to have one-way
operations. If you break a teacup, you can't put it back together.
Entropy is directional, right? How does Proteus address this?
In fact this is the case. However, if that's the level of modeling we
want to achieve, I think we will be out of luck. Let's make an example
of a gas expanding in a room, which is much easier to model than the
cup breaking (conceptually there is just a little difference). Imagine
the gas expanding from being all concentrated in point A (a small
volume) to the whole room. Microscopically, gas expansion is
reversible. Macroscopically it's not. What this means microscopically
is that the number of gas molecules is so large (say, of the order of
10^23) that the state "all the gas goes back to point A" is very
unlikely (let's say: really impossible) to happen. So a microscopical
model (with ~ 10^23 molecules) does not need to bother with
irreversibility. However, if we would like to have a macroscopic
model, with much less states (and memory usage) we have to model
irreversibility explicitly, This is Physics (did I tell you that I am
a Physicist?) Now what to do in proteus, I don't know.
Have a good night!
Davide
a group extension is a general means of describing a group in terms of a particular normal subgroup and quotient group. If Q and N are two groups, then G is an extension of Q by N if there is a short exact sequence
he definition that a group extension is a general means of describing a group in terms of a particular normal subgroup and quotient group. If Q and N are two groups, then G is an extension of Q by N if there is a short exact sequence
A group (G, •) is a set G closed under a binary operation • satisfying the following 3 axioms:
Quick question, though. We can't always assume 2=2, but can we always
assume *16+2=*16+2?
I'll chat with some of my friends in the UCD math department to see if
they can offer any insight into group extensions.
Quick question, though. We can't always assume 2=2, but can we always
assume *16+2=*16+2?
I don't and my math friends specialize in different fields, sorry :-(