Random Thoughts

# Robotics Thought Experiment

With the ever growing field of artificial intelligence, it’s not only necessary but also crucial to evaluate what lies in front of us, the tangible future when robotics become so abundantly available that all low level labours are replaced by robotics. What’s the implications of such scenario and how will it impact our daily life? Let’s have a fun thought experiment.

Imagine that the world has been running happily as the way it is for an indefinite amount of time, until one seemingly unspectacular morning, when everyone wakes up and sees a massive amount advertisements from a company called RoboticX featuring their \$99 robotics that are demonstrated to accomplish almost all low level human labour such as manufacturing daily products, undertaking construction works, etc. The Owners of manufacturing companies will think, “Jeez! It’s so cheap! Why am I still hiring workers! I don’t want to pay for their freaking health insurance!”. Owners of construction companies will think, “Jeez! It’s so cheap! Robots don’t get accident! Robot works 24-7!”. Next day, all manufacturing and construction workers lost their jobs. How many are they? Not too many, just about one third of the world population.

Next day, everywhere on the streets you will find people crying and protesting against RoboticX which is claimed to be the sole trigger of the disaster. RoboticX doesn’t even bother, and the protesters don’t seem to get much government support. Soon the protestors realize that “Wait a sec! RoboticX is getting so rich and they are paying a lot of tax! The government is also getting rich!”. Soon the protestors redirect their fire to the government, “Government is conspiring with RoboticX! They want us to lose our jobs so they can all get rich!” Stress from one third of the population is certainly strong enough to shake any government. New politicians start to emerge and get strong support by advocating “No Robot Movement”. To compete with them in president election, the party in charge is also forced to restrict the use of robots and place heavy constraints on RoboticX. The story ends with Robotic getting a bankruptcy due to heavy political constraints and lack of people support. The world is back to the old and happy way as it was for an indefinite amount of time.

Although being an imaginary thought experiment, it occurs to me clearly that our present political structure is no longer fit for a technology dominated future. The fact that all politics are local but all economics are global is one of the biggest paradoxes in the present political environment. Singapore is a good example of such paradox. As a small island with limited human resources, Singapore has to rely on importing foreign talents from nearby countries to boost its economics. At the same time it also means that many Singaporeans’ jobs are taken up by foreigners. As a local nation deemed to serve the benefits of its local people, Singapore government faces heavy stress from Singaporeans and are forced to place constraints on importing foreigner talents which may likely to slow down Singapore’s economic growth. Such paradox exists everywhere in the political world. The problem may lie in the very notion of country itself which has its origin in the prehistorical times when forming a tribe is crucial to survival, but is such an old notion still adequate to support human being’s continuous development after we have witnessed such immense advancement in the technology world? Shouldn’t we rethink about our political structure in an ever-growing global economy?

Having read so many unfortunate stories in wars, I truly look forward to a global political reform.

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Random Thoughts

# Interstellar

I watched this movie last week. I guess it’s now an appropriate time to write a little about it without spoiling the fun of some. Walking out the theater, I have nothing in mind but a deepest respect for the director Christoper Nolan. How remarkable is his imagination! Everything springs out of fundamental principles in physics, being creative but not absurd. How dazzling is the ring of light surrounding the gigantic black-hole! How magnificent is the journey through the wormhole, full of lavishly blossoming optical illusion! How marvelous is his world beyond the event horizon, scientifically known to permit traveling through time! The ordinary concept of distance and time vanishes in a cosmic scale, and it is exploited exquisitely in the movie with no lack of an emotional touch. What I found the most remarkable is the effort that the production team puts in to elevate ordinary people from their daily necessities to ponder upon the alluring wonders of our universe. Such contemplation, followed by a careful reflection, will surely give people a better perspective into many important aspects of our ordinary life.

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Random Thoughts

# An Interesting Maths Problem

There was one day when i walked into SPS room I saw this question on the whiteboard, Anyone can prove that

$\sqrt{1+2\sqrt{1+3\sqrt{1+4\sqrt{...}}}}=3$

I knew it’s a waste of time to work on this and it doesn’t seem to carry any physical significance, but I just couldn’t help thinking about it and trying to figure it out! Is it a disease?

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Random Thoughts

# Two Commutation Relations

In previous post I mentioned that the First Commutation Relation and Second Commutation Relation are equivalent. Here is a proof from Classical Perspective.

We assume one of them to be true. For example, we assume First Commutation Relation to be true. i.e.

$[\hat{x}, \hat{p}] = i\hbar\rightarrow \hat{p} = -i\hbar\frac{\partial{}}{\partial{x}}$

Classical Hamiltonian is given by

$\hat{H} = \frac{\hat{p}^2}{2m} + \hat{V} = -\frac{\hbar^2}{2m}\frac{\partial{}^2}{\partial{x^2}} + V$

We next compute the commutation between Hamiltonian and Position

$[\hat{H},\hat{x}] = [\frac{\hat{p}^2}{2m} + \hat{V},\hat{x}]=\frac{1}{2m}[\hat{p}^2, x] =i\hbar\frac{\hat{p}}{m}$

We see the operator in the last term is precisely the velocity operator $\hat{v}$

$\hat{v}\psi = v\psi$

Therefore from definition of velocity

$\hat{v}\psi = \frac{\partial{x}}{\partial{t}}\psi = [\frac{\partial{}}{\partial{t}}, \hat{x}]\psi$

So we conclude that

$[\hat{H},\hat{x}]\psi = i\hbar[\frac{\partial{}}{\partial{t}}, \hat{x}]\psi$

$\hat{H} = i\hbar\frac{\partial{}}{\partial{t}}$

It then follows

$[\hat{H},\hat{t}] = [i\hbar\frac{\partial{}}{\partial{t}}, \hat{t}] = i\hbar$

Equivalence proved.

(Note it’s only proved for non-relativistic hamiltonian, i still haven’t worked out the most general case at the moment)

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# On Schrodinger Equation

There is a concept in Schrodinger equation that has never been taught in any of my Quantum Mechanics lectures.

We assume the validity of the following commutation relation

$[x, p] = i\hbar$

We call it First Commutation Relation. Equivalently we conjecture the validity of another commutation relation

$[H, t] = i\hbar$

We call it Second Commutation Relation. Based on these two assumptions, we build up Quantum Mechanics as follows

From First Commutation Relation:

$[p, x] = -i\hbar \rightarrow p = -i\hbar\frac{\partial{}}{\partial{x}}$

From Second Commutation Relation:

$[H, t] = i\hbar \rightarrow H = i\hbar\frac{\partial{}}{\partial{t}}$

From Classical Mechanics, the definition of Hamiltonian for a particle is

$H = \frac{P^2}{2m} + V$

Substitute H and P into this equation

$H=\frac{P^2}{2m} + V = -\frac{\hbar^2}{2m}\frac{\partial{}^2}{\partial{x^2}} + V = i\hbar\frac{\partial{}}{\partial{t}}$

This produces Schrodinger Equation. Next we consider the case for photon. The Hamiltonian for photon is given by Einstein’s Special Theory of Relativity

$H^2 = p^2c^2 + m^2c^4$

Since photon has no mass

$H^2 = p^2c^2$

Substitute our formula for Momentum and Hamiltonian

$H^2 = -\hbar^2\frac{\partial{}^2}{\partial{x^2}}c^2=-\hbar^2\frac{\partial{}^2}{\partial{t^2}}$

We can easily see

$\frac{\partial{}^2}{\partial{x^2}} = \frac{1}{c^2}\frac{\partial{}^2}{\partial{t^2}}$

It reproduces Maxwell’s Light Equation. Given a standard EM wave equation to be

$\psi = Ae^{i(kx - wt)}$

We can find its energy by hamiltonian operator

$H\psi = i\hbar\frac{\partial{}}{\partial{t}}Ae^{i(kx-\omega t)} = \hbar\omega\psi \rightarrow E=\hbar\omega$

It predicts correct energy of each photon as predicted by Einstein and Planck.

As a concluding remark, the assumption of the validity of two commutation relation turns out to be generally true even in relativistic case. Interestingly, one can also show that the two commutations are essentially equivalent. Dropping the First Commutation Relation, our Quantum Mechanics builds itself upon the incompatibility of energy and time, which it’s absolutely mysterious, utterly intriguing and extremely suggestive that an internal structure of space-time must remain undiscovered that governs this incompatibility.

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Random Thoughts

# Principle of Concentration

We first define a term called Interest to represent one thing that a person may potentially doThen we collect all Interests of a person, and organize them in such a way that associated Interests are interconnected. This will give us a huge network of Interests. We then topologically fold our network of Interests into a multidimensional space while keeping connected Interests as adjacent points in space. This space formed is called Interest Space.

Each person is represented as a collection of N Interest points living freely in the Interest Space. We assume each Interest point has equal probability of moving in any direction in the Interest Space. Given N>>1 we can approximate the distribution of  Interest points by a continuous function which we call Concentration Function, represented as C(x,t),

$C(\mathbf{x}, t) = C(x_1, x_2, ... , x_d, t)$

$\int_V C(\mathbf{x},t)d\tau = N$

where d is the dimension of Interest Space, and ${x_1, x_2, ... , x_d}$ represents a coordinate and $d\tau$ represents a unit volume in Interest Space.

Random walk of Interest Point

As the name suggests, the magnitude of Concentration Function will represent the level of concentration at the specific interest point. Our assumption is that each interest point has equal probability of moving in any direction. Anyone with a basic physics training will immediately realize that it reassembles a random walk. For a simplified case where d = 2, it implies a person’s concentration, which is initially at the origin, will move around like shown in Fig. 1. It shows how our concentration will be digressed graphically.

Fig 1: “Random Walk” of Interest Point. Image adapted from Wikipedia http://en.wikipedia.org/wiki/Brownian_motion

Diffusion of Concentration

When we have a collection of N interest points diffusing simultaneously from the same interest point, from statistics, they follow a Gaussian distribution around the initial interest point, and get flattened through time.

Fig. 2 Qualitative feature of concentration diffusion. (Note the axis labels and time scale don’t correspond to our discussion) Image adapted from Wikipedia: http://en.wikipedia.org/wiki/Brownian_motion

Diffusion Equation of Concentration

An important feature of our construct is the Finiteness of a person’s Interest Points. In other words, we enforce a Conservation of Interest Points. Together with our assumption that each interest point has equal probability to diffuse into its adjacent points, it’s easy to show that our concentration function must follow a continuity equation.

$\nabla^2 C(\mathbf{x},t) = D\frac{\partial{}}{\partial{t}}C(\mathbf{x},t)$

To simplify the problem, we first investigate a one dimensional model. Assuming there is no Boundary Conditionswe can solve the equation with standard separation of variables technique. Given a constraint that C(x,t) must remain real, we get the solution to be like

$C(x,t) = const. cos(kx - \frac{k}{\sqrt{D}}t)$

I call this equation Freeworking Equation as we impose no constraints on interest space and time. The implication is that during freeworking, our concentration on any specific interest point will fluctuate sinusoidally with time, and our concentration will fluctuate through related interest points sinusoidally. All these make sense to me.

Fig. 3. Cosine function. Illustration that concentration fluctuates through interest points. Image adapted from: http://www.biology.arizona.edu/biomath/tutorials/trigonometric/graphtrigfunctions.html

Importance of boundary conditions

From previous discussion, when there is no constraints, concentration merely fluctuates indefinitely throughout space and time. So here comes the question, how do we raise our concentration on a specific interest point? This is when boundary condition starts to play an important role.

Suppose we have such a constraint that anything outside interest points A and B will be completely ignored. The solutions start to look like in Fig. 4. Compared with our freeworking equation where our concentration merely flows around indefinitely, now they become localized in a certain region. A remarkable fact is that now the solution form a complete set of fourior basics that are able to compose any functions within A and B. Similar effect happens if we constrain our time, we could arbitrarily concentrate on any interest point within A and B.

Fig. 4 Constrain our concentration that any interest points outside A and B will be ignored completely. Our concentration function will look like this. Image adapted from http://webs.morningside.edu/slaven/Physics/atom/atom5.html

What does it mean after all?

We have proved that to raise concentration on a specific interest point, we constrain our interest space and time. This is exactly the rationale why we often have to constrain ourselves by setting rigid deadlines and ignore irrelevant topics to be arbitrarily concentrated and therefore achieve great things.

One may ask if we have enough time, why should we care about productivity at all? The ultimate reason is the intrinsic constraint of our lifetime. We simply don’t have enough time. That’s how nature made it to be, neither too short that we can’t achieve anything, nor too long that our concentration starts to diffuse. Nature simply assigns each species an appropriate time scale in preference of productivity. It’s absolutely fascinating!

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Random Thoughts

# Some entertainment

It’s a rainy day. In California it’s rare. I felt reluctant to go to my martial art class because I am unwilling to rush in the rain and potentially get a cold. I decided to stay in the bed and entertain myself a little bit by writing this post.

The question that I want to attempt is

Why can’t we live forever?

The motivation comes about when I wonder why life has to be bound by such a restricted time frame, and wonder what would happen if we could live forever. This post serves as an introduction to the following discussions on my theory of life, in which I  conjecture how life works in its most fundamental form.

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