quarterwave

This is in fact a profound question.

The physics of electricity propagation in a powerline circuit is fundamentally the same as the propagation of FM radio waves, or even the beam from a flashlight. All of these examples involve electromagnetic energy propagating at the speed of light. So why do we need wires for powerlines, but not for propagating radio signals or light beams?

The principle is that light (in a vacuum at least) travels at a constant but non-infinite velocity, c. Hence, the electrical wiggle received at an observer's location now i.e; (x,t), has been caused by some earlier wiggle conducted by the source (x',t') such that the t-t'=(x-x')/c. We should expect that the effect of this 'time delay' is more profound if the source is wiggling faster in time.

A more specific way to state this is that the electromagnetic power radiated into free space by a dipole increases as the square of the dipole moment and the fourth power of the frequency. Now compare a powerline (60 cycles/sec), with FM radio (100 Million cycles/sec), and with the light from a flashlight (500 Trillion cycles/sec). That's why even atomic dipoles can produce intense visible light, while it would take a very very large dipole to radiate a similar intensity at 60 cycles.

Feynman Lectures Vol.II is absolutely the best reference to learn this stuff.

That is not to say that a bird needs to make contact with two wires on a utility line, in order to suffer harm. If the line voltage is high enough (e.g; 110,000 Volts, as in high-tension power transmission), an electrical corona would form around the line from electrostatic effects. The corona is actually ionized air indicating the high electrostatic field strengths in the region, it can emit a bluish glow and growl at 60 cycles. Birds can no doubt sense this corona & stay away.

Erlang = Owls (message passing)

Crystalline III-V channels can be grown epitaxially on silicon substrates, with buffer layers to grade the strain due to crystal lattice mismatch. With silicon wafers heading to 450mm diameter the economics would argue against native III-V substrates.

One advantage of native III-V substrates is they are semi-insulating (very high resistivity) so there is no need for transistor isolation wells. However, insulated substrates could be obtained on silicon by means of wafer bonding with an intermediate dielectric layer.

I am reading this book 'The Dollar Trap: How the US dollar tightened its grip on global finance' [1], where economist Eswar Prasad explains how money flows into the US from around the world even when troubles originate in U.S financial markets.

[1] http://thedollartrap.com/

Thanks, good point about telcos.

Interesting work!

At first glance it would seem that Erlang or Akka provide a proven infrastructure for building such a multi-agent system+. Yet, a key construct is the notion of time and its passage.

(+Which is subtly different from an agent-based model, for simplicity let's assume they're both the same thing.)

There is a profound observation by Rich Hickey in his talk [1] 'Are we there yet? - A deconstruction of object-oriented time' (the baseball field slide): "Perception is massively parallel and requires no co-ordination - This is not message passing!"

For example if the said ballpark suffered an earthquake, would the Matrix need to pass messages to each agent? Would a spectator continue walking toward the hot-dog stand just because the message hasn't shown up yet?

From this perspective, the notion of 'container clock' presented here can be useful. Question is whether we 'get to stop the world when we want to look around' (Hickey), or not.

[1] http://wiki.jvmlangsummit.com/images/a/ab/HickeyJVMSummit200...

I have home back-up power based on an inverter charging a lead-acid battery (located in a sheltered area outside the home), which costs about $100/kWh. Usage is about 1-2 hours discharge per day. No matter how well serviced, I've found these batteries don't last beyond four years. Hence I'd pay even $400/kWh for a well-engineered deep-cycle battery that is safe, maintenance-free, and will last at least 10 years. Excluding balance of system, even.

This is an excellent 'road map' to the two key theorems of information theory.

The focus on decoding complexity in the noisy coding theorem is particularly welcome. A separate article amplifying just this aspect (error exponent, Pareto complexity, etc) would be welcome.

Thanks for this reference.

Thanks for the detailed perspective.

My limited & roseate view of a 21st century Lisp machine is based on an old theme - a massively parallel computing system using bespoke silicon logic blocks.

As you have noted below, not only are the cache sizes in a modern CPU monstrous, there's also the compilers optimized for these caches, instructions, branch prediction units, etc. No point in ending up with a chip that is much slower than an equivalent one running on a specially-designed virtual machine, which is itself much slower than MPI.

Dreaming on, such a Lisp machine would need a vast collaborative academic effort with substantially new IP design, in say the 32nm silicon process node. That's the most advanced node where lithography is still (somewhat) manageable for custom IP design.

Any chance of a resurgence in Lisp machines? Especially in view of the changes in CPU architecture due to semiconductor scaling challenges.

i used to be a college teacher for several years & my sympathies are with the author.

Advice for those considering this path in science/tech - learn to write code on the side. Pick something mainstream that will be around for a while, and which you can tap for a sideline. Develop deep expertise, spend as much time continually educating yourself as you do for others.

That's correct, thanks for pointing it out.

Is there an Erlang shell to evaluate expressions?

There seems to be a sub-window to the right of the module editor, but I'm unable to place the cursor there.

Tried in both Firefox 35 and Chrome 39.

While the Jeeves stories are good, they can't hold a candle to the time when lawlessness raised its head at Blandings Castle, or to the effect of Mulliner's Buck-u-Uppo tonic on the Bishop and the Vicar (quoting from memory, e.&o.e):

"Tell him we're a couple of cats"

"We're a couple of cats"

"Oh, that's all right then" said Mulliner as he stood aside to let them in. The Bishop, being an artist at heart, mewed as he climbed in, to lend verisimilitude to the deception.

A perfect storm of wonderful English prose with a boundless absurdity of form and circumstance.

Thanks for pointing this out.

The role of muon instead of proton could be: (i) to make the bond detectable as the muon decays, or (ii) 10X lighter mass of muonium compared to regular hydrogen leads to a dynamical regime with saddle points in P.E vs K.E (as pointed out earlier).

Thanks for both explanations.

Why is the muonic hydrogen required?

From the Bohr formula the Rydberg energy of the muonic hydrogen would be some 200 times larger than regular hydrogen. Anyone know how that plays a role?

It can't be sqrt(spring/mass) for vibration since the proton is anyway already some 2000x heavier than the electron. Unless spring somehow depended on the Rydberg energy, which is possible since the P.E-K.E would depend on mass via the K.E.

The DSL reminds me of Fenics http://fenicsproject.org/

Thanks for the clear reply. I also read your paper. Immutable should be adequate for avoiding the serialization tax in hybrid applications that need 'symmetry breaking' of location transparency.

Can Orleans grains within a single thread share state without message passing via the interface?

Processor clock frequency scaling is limited by two factors: (i) logic signal delays, and (ii) processor power dissipation (heat).

In broad brush strokes, a processor core needs to shunt buses of signals across several timing domains. Due to process, voltage, and temperature (PVT) variations the wire delays exhibit variations at several levels - across chip, chip-to-chip, supply voltage, etc. Think of football teams from different cities taking multiple airline flights to get to the same ballpark, with the possibility of bad weather causing a flight to be cancelled, etc. To ensure that signal buses from different domains rendezvous 'on time', the season schedule has to provide for 'timing slack'. The process of intentionally adding little gate delays here and there to increase the timing slack across the entirety of a large chip is known as timing closure, and is achieved using sophisticated design algorithms. As clock frequency increases, the timing closure literally hits a brick wall - beyond some GHz number the slack rapidly plummets to zero, goes negative.

Increasing supply voltage can make the transistors go faster. Think aircraft flying faster by burning more fuel and you can see how that improves timing slack, but also increases the power dissipation. As heat increases, there is a vicious cycle - the leakage current of transistors in the OFF state increases - which doesn't cause a core meltdown, but makes the power dissipation scale viciously with voltage. Transistor reliability is also degraded, which is why data centers can't afford to overclock the way a gaming enthusiast might.

Net is that in a synchronous design paradigm (multiple clock domains, but not asynchronous logic), any easing of the timing closure brick wall is useful for designs chasing frequency. Photonic buses, even at high baud rates, must still be wide enough to avoid a serialization latency tax.

However, if the architecture prefers to keep the clock frequency lower and increase core count within the same chip thermal budget (TDP), then photonics may be limited to inter-core buses (which are not sensitive to timing on the scale of a clock period).

I don't have much idea about how all this works with asynchronous logic, perhaps someone else can comment.

Feynman-II has a nice chapter describing the idea of curved spaces: http://www.feynmanlectures.caltech.edu/II_42.html

The chapters on electromagnetism and special relativity are outstanding: starting with why the magnetism we observe around a wire carrying current is a v^2/c^2 effect, and proceeding all the way to how the electric and magnetic field intensities are both part of an electromagnetic tensor. And then the field-versus-potential question, leading to a discussion of the Aharanov-Bohm effect, etc.

The discussion on the classical theories of the electromagnetic self-energy of an electron is outstanding. It's in Vol.II that we really understand how much this guy had thought through the stuff, he wasn't just drawing squiggly lines to calculate some numbers.

Would the symmetry groups (point groups?) be different for 3D?

The impedance of free space is (unfortunately) a few hundred ohms. On top of this, the minimum signal voltage of analog integrated circuits is set by unsystematic (random) offsets, which get worse as transistor sizes shrink. It's possible to mitigate these offsets by circuit techniques, but they cannot be eliminated.

Near-field radio can break free of the impedance constraint (which applies only to far-field TEM waves), but antenna area sets signal level, as in flux=intensity*area. Why make a tiny chip when the antenna needs to be the size of a quarter?

It's not easy to design radio chips for either of these scenarios. Pushing the radio burden onto the DSP consumes power on the digital side, so no easy way out.

[Aside: Referring to a recent thread on measurement of the Planck constant, the ratio of the impedance of free space to the Hall resistance turns out to be the dimensionless fine structure constant, alpha. This alpha sets the coupling strength of an electron and photon in the quantum theory of electrodynamics, and the 'Taylor series' for the self-energy of an electron converges because alpha is much less than unity. Feynman diagrams are a way to keep track of terms in that Taylor series, to ensure that the Schrodinger equation is kept consistent with special relativity, etc.]

Consider the use case suggested by the image on the copy i.e; on-screen projection of slides in a business meeting. Can this use case be met with a tablet/smart phone using a VGA adapter?

Nice trick, to cancel the e^2 from (h/e)^2 and h/e^2 to give h, and do it a way accessible to a basic laboratory.

The interesting thing about h/e^2 as Hall resistance is that it's an off-diagonal term in the Onsager matrix, while here it is used to balance a diagonal term i.e; work.

Equally nice is to consume Newton's gravitational constant in g, the acceleration due to gravity, because somewhere the mass needs to come out, and there is no mass in the Maxwell equations. The Planck voltage sqrt(Ge^2/(hc^5)) is very small (compared with electrochemical potentials): 3.3e-29 Volts.

"Finding talent in Hi Tech centers like Bangalore is almost as hard as finding qualified people in Silicon Valley."

This is a good point. A related question: Can more and better work be done by less people?

If so, are 'two-dozen dev-ops' (a rhetorical number) adequate for all scenarios?

Yes, agree that log() wouldn't result from a linear operator.

The idea behind my question: does the Shannon entropic integral correspond to the L2 length of some projected state? Leading to a prescription to prepare a state with minimum uncertainty product of canonically conjugate physical quantities.

Afaik, in classical statistical physics the log() shows up when the N! in a binomial probability distribution limits to large N via the Stirling approximation. It would be interesting to find a different route for log() to enter the picture from a quantum standpoint.

All admittedly vague and hand waving speculation.

@obastani : very good comment.

Aside: If |Psi> is a state with wavefunction <x|Psi>, then is there a linear operator A such that <x|A|Psi> = log(<x|Psi>)?

Note: Logarithm of a complex function.