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A single mom who’s working two jobs and still finds time to take her son to practice, that’s a miracle. A teenager who says ‘no’ to drugs and ‘yes’ to an education, that’s a miracle. People want me to do everything for them. What they don’t realize is they have the power. Want see a miracle, son? Be the miracle.
— God, Bruce Almighty
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2009.12.10 Thursday
A Fock state (also known as a number state), in quantum mechanics, is any state of the Fock space with a well-defined number of particles in each state.
— Wikipedia on Fock state
2009.12.09 Wednesday ACHK
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說話不流利是因為想同一時間講超過一個字.
做事不暢順是因為想同一時間做超過一件事.
— Me@2009.12.09
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2009.12.09 Wednesday
In quantum mechanics, a stationary state is an eigenstate of a Hamiltonian, or in other words, a state of definite energy. It’s called stationary because the corresponding probability density has no time dependence.
As an eigenstate of the Hamiltonian, a stationary state is not subject to change or decay (to a lower energy state). In practice, stationary states are never truly “stationary” for all time. Rather, they refer to the eigenstate of a Hamiltonian where small perturbative effects have been ignored. The language allows one to discuss the eigenstates of the unperturbed Hamiltonian, whereas the perturbation will eventually cause the stationary state to decay. The only true stationary state is the ground state.
— Wikipedia on Stationary state
2009.12.08 Tuesday ACHK
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Be always ready.
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2009.12.08 Tuesday
Every two level system can be regarded as a spin.
— Wang Dawei@2009.11.30
2009.12.07 Monday ACHK
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Other artists understand that they need to see the edges of the box if they’re going to create work that lasts.
No fence, no art.
— Seth Godin
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2009.12.07 Monday
The lapses in intuition mostly stemmed from the fact that the limit of an infinite statistical system has many zero-one laws which are absent in finite systems: an infinitesimal change in a parameter can lead to big differences in the statistical behavior, as Democritus expected.
— Wikipedia on Ising Model
2009.12.06 Sunday ACHK
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「原色」並非是一種物理概念，反倒是一種生物學的概念，是基於人的肉眼對於光線的生理作用。
有些物種的眼球具有四種不同的「感光體」，例如許多鳥類及有袋動物都屬於這類生物，甚至於有人提出部分女性人類的眼球也具有第四種感光體，除了紅綠藍之外還多了黃色。另一方面，大多數的哺乳動物都是屬於「雙色感光體生物」，牠們的眼球只有兩種感光體。
— 維基百科
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Primary colors are not a fundamental property of light but are often related to the physiological response of the eye to light.
Many birds and marsupials are tetrachromats, and it has been suggested that some human females are tetrachromats as well, having an extra variant version of the long-wave (L) cone type.
— Wikipedia on Primary color
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2009.12.06 Sunday
While a magnetic monopole particle has never been observed, there are a number of phenomena in condensed-matter physics where a material, due to the collective behavior of its electrons and ions, can show emergent phenomena that resemble magnetic monopoles in some respect. These should not be confused with actual monopole particles; in particular, the divergence of the microscopic magnetic B-field is zero everywhere in these systems, unlike in the presence of a true magnetic monopole particle. The behavior of these quasiparticles would only become indistinguishable from true magnetic monopoles — and they would truly deserve the name — if the so-called magnetic fluxtubes connecting these would-be monopoles became unobservable which also means that these flux tubes would have to be infinitely thin, obey the Dirac quantization rule, and deserve to be called Dirac strings.
— Wikipedia on “Monopoles” in condensed-matter systems
2009.12.05 Saturday ACHK
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Time is a great teacher but it kills all its students.
— H. Berlioz
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2009.12.05 Saturday
The Fock space is an algebraic system used in quantum mechanics to describe quantum states with a variable or unknown number of particles. It is named after V. A. Fock.
Technically, the Fock space is the Hilbert space made from the direct sum of tensor products of single-particle Hilbert spaces:
…
— Wikipedia on Fock space
2009.12.04 Friday ACHK
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Give me a million dollars and I’ll figure out what to do. But it’s harder than it looks. Constraints give your life shape. Remove them and most people have no idea what to do: look at what happens to those who win lotteries or inherit money.
— How to do what you love, by Paul Graham
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2009.12.04 Friday
Neutrinos could also be used for studying quantum gravity effects. Because they are not affected by either the strong interaction or electromagnetism (unless they have a magnetic moment), and because they are not normally found in composite particles (unlike quarks) or prone to near instantaneous decay (like many other standard model particles) it might be possible to isolate and measure gravitational effects on neutrinos at a quantum level.
— Wikipedia on Neutrinos
2009.12.03 Thursday ACHK
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Resistance to the organized mass can be effected only by the man who is as well organized in his individuality as the mass itself.
— Carl Jung
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2009.12.03 Thursday
In fact, the spectrum of interpretations in quantum mechanics has a close analogue in probability theory.
Note that anyone who acted that way would be silly, and that their error would have little to do with QUANTUM MECHANICS, but mainly with PROBABILITY THEORY. Probability theory is the special case of quantum mechanics in which ones algebra of observables is commutative. (This becomes a theorem in the context of C*-algebra theory.) Quantum mechanics has special features due to the noncommutativity, but probability theory already exhibits certain subtleties of interpretation, which I believe are a large part of what’s at stake here.
— John C. Baez
2009.12.02 Wednesday ACHK
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Emerson presupposes that the mind is initially subject to an unhappy nonconformism. However, “Self-Reliance” is not anti-society or anti-community. Instead, Emerson advocates self-reliance as a starting point, not as a goal.
— Wikipedia
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2009.12.02 Wednesday
Since in some sense the interaction picture can be thought of
as rotating with the system ket
only that part of the electromagnetic wave that approximately co-rotates is kept;
the counter-rotating component is discarded.
— Wikipedia on Rotational Wave Approximation
2009.12.01 Tuesday ACHK
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An institution is the lengthened shadow of one man; as, Monachism, of the Hermit Antony; the Reformation, of Luther; Quakerism, of Fox; Methodism, of Wesley; Abolition, of Clarkson. Scipio, Milton called “the height of Rome”; and all history resolves itself very easily into the biography of a few stout and earnest persons.
— Ralph Waldo Emerson
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2009.12.01 Tuesday
Physics Town 