# Tag Info

106

What you're looking for is Landauer's principle. You should be able to find plenty of information about it now that you know its name, but briefly, there is a thermodynamic limit that says you have to use $k_BT \ln 2$ joules of energy (where $k_B$ is Boltzmann's constant and $T$ is the ambient temperature) every time you erase one bit of computer memory. ...

23

1) yes, it basically will find a non-optimal solution. At every point, the top of the ray looks for the bigger potential gradient, the charge in the surrounding volume grows, polarizing surrounding material (air, in this case) until a bigger gradient shows up and the ray continues over that direction. This is why the lightining path looks like a jigsaw; its ...

18

I think perhaps some of the other answers are taking computer science to be synonymous with computation. I guess that this is perhaps not what you mean, but rather theoretical computer science. There is obviously a huge overlap with quantum information processing of which I think you are already well aware, so I will ignore that. Much of physics (including ...

18

Some software I have used or has been recommended to me for physics-related work: WolframAlpha -- when I don't have Maple around, I use it for simple symbolic calculations Maxima -- free open source alternative to Maple/Mathematica DataMelt -- another free and open-source software that runs under the Java platform on all Java-supported OS Sage -- quite an ...

12

First off, physics tends to provide a very good background for people who move on to study problems in other areas, which is perhaps why there is a lot of cross-over to computer science. However, there are also a number of areas at the interface of computer science and physics which attract people from both sides: Computer hardware (which is generally ...

12

Assuming a typical computer with CPU processing power ~1 GHz. It means that it can generate output byte sequence at ~$10^9$ byte/s, which is about ~$10^{-13}$ J/K in terms of von Neumann entropy. Also, the power consumption of a typical CPU is ~100 W, which gives entropy ~0.3 J/K at room temperature. So the (minimum ΔS) / (actual ΔS) ~ $10^{-14}$ This ...

10

EDIT: This answer is specifically from the perspective of very computationally oriented fields like theoretical plasma physics. Most physicists can program, and in fact many are rather good programmers. It would be difficult to work in modern physics without being able to program. Unfortunately, many are also not terribly good programmers (I've read many a ...

10

Some info from ASIC world: For example, you processor have 300 mil. transistors, and most of these do some work. But, in order to make for example pure 32-bit add operation you need just about 1000 of them. Others are for caching and passing data back and forth - support functions which are impossible to estimate. So estimations from math side are very hard ...

9

It is probably worth your while to buy Mathematica, Maple, or Matlab, depending on your needs. I wish it weren't so, but this is one area in which the commercial tools are still vastly better than their free counterparts. If you are a student, you can buy these at fairly afforable prices. Maple 14 Student Edition is only \$99. Mathematica for Students is ...

8

I've recently discovered Cadabra. A field-theory motivated approach to computer algebra I'm really impressed.

7

There's no flaw in your argument. A computer heats the room just as effectively as an electric heater of the same power and you could use the computer to do something useful (Bitcoin mining?) while it's heating your room. There are some practical considerations, though I think these have been sufficiently discussed in the comments. Computers would make for ...

6

Sage is a Python based system (including Numpy and Scipy) which includes a symbolic computation module. From the Sage homepage: Sage is a free open-source mathematics software system licensed under the GPL. It combines the power of many existing open-source packages into a common Python-based interface. Mission: Creating a viable free open source ...

6

I'd like to add that GNU Octave is a very good free alternative to Matlab. Contrary to Scilab which does not aim at being compatible with Matlab, you can practically run your Matlab scripts with Octave with very few modifications (at least with their latest version).

6

This is, no doubt, one of the biggest challenges for realistic simulations: waves crashing, hair moving under wind and whatever other movement involving turbulence will be hard to solve. Though it is true that one can solve the equations of motion for each individual particle in a 'molecular dynamics' fashion, that is just infeasible for a system that goes ...

5

Color forces are not like electromagnetic ones. There exist no unbound color carrying particles analogous to the electron, because the forces increase with the distance rather than decrease and collective effects appear only within nuclei through residuals of the colored forces which attract the nucleons and hold them in the nuclei. Collective effects ...

5

For modeling of physical (and chemical) systems on quantum computer even 25-30 qubits would be already quite nice, see Lanyon, et al, “Towards Quantum Chemistry on a Quantum Computer”, Nature Chemistry 2, 106 - 111 (2009) (see also http://arxiv.org/abs/0905.0887 ) Really, quant-ph section in arXiv.org is standard place for papers about quantum computers, ...

5

You can do all kinds of things like that, but in the end you will find yourself returning to electrons. Using light in particular is not a very good idea because it is very hard to do non-linear operations with it. Almost all non-linear effects require a very large number of photons (I would guesstimate on the order of 1e8 or more), whereas one can ...

4

For all practical purposes today the answers above are very informative. However, as Marek has pointed out above, your fundamental theoretical model of the thermodynamics of computation, on which you are basing the question is, surprisingly, wrong, as we first began to discover 50 years ago (see refs. to Landauer Charlie Bennet, Friedkin, others). ...

4

I think the main reason why this is so common is that many people who are of the tenured professor age now (50-60) were in graduate school before most colleges offered a Ph.D. in computer science. So back then, people who were interested in theoretical computer science got their doctorate in Mathematics, and people who were interested in applied computer ...

4

From my reasoning and knowledge of one CS professor who has a PhD in astronomy: Above all, the answer depends on your definition of what a "computer scientist" is. What do you mean by "computer scientist"? Someone who does research in a computer science department? Or does perhaps artificial intelligence, algorithm development, or grid computing for a ...

4

Human power consumption can be guesstimated as 100W, similar to the power consumption of an ordinary computer, plus or minus a few orders of magnitude depending on one's idea of "ordinary". A computer can do billions of flops per second, and it would take me many seconds or minutes to perform one with pen and paper, and furthermore I will make many more ...

4

Can physical states be treated as information (strings over some alphabet)? There is a distinction between a state and a vector (see this mo question), but disregarding that, we can clearly approximate a vector to any desired precision using a finite-length string. I doubt that anyone can say whether the rounding errors involved grow uncontrollably or ...

4

Although in one sense this question and answer is altogether beyond physics, (as discussed below) there would seem to be a very natural answer to this question, to wit: Beyond Quantum Computers are computers than can overcome the Church-Turing thesis (See the Wikipedia page with this name) and, more generally, can compute the truth value of propositions ...

4

I think that Wolfram is arguing that the study of cellular automata and perhaps similar computational systems could serve as an organizational principle, providing a coherent framework to look at different problem (just like the more familiar frameworks provided by physics and chemistry). This explains the title of his new book, A new kind of Science (i.e. ...

4

From the Wikipedia article Alan Turing proved in 1936 that a general algorithm to solve the halting problem for all possible program-input pairs cannot exist. Therefore, a solution to the halting problem for the particular pair of initial conditions and laws of motion associated to our universe (if such a thing even really exists) actually would not ...

3

The brain is massively parallel, so it tends to come out looking very good. The OP suggested using joules/flop as the measure of (in)efficiency. This leaves considerable ambiguity. I believe the way neurons typically work is that they form something like a weighted average of their binary inputs, and generate a binary output that is based on a threshold ...

3

GiNaC is a c++ symbolic manipulation framework oriented to high-energy physics computations. It has a couple of interactive frontends, although its main usage is as part of the Root framework at CERN. A derivative of GiNaC is Pynac, which forms the backend for symbolic expressions in Sage.

Only top voted, non community-wiki answers of a minimum length are eligible