**String Theory**

I would not even be prepared to call string theory a “theory.” Just a hunch. ~ Gerard ‘t Hooft

String theory postulates subatomic particles as infinitesimally thin strings vibrating through a holistic dimensionality (HD) that has more than 4 dimensions.

We still don’t know what string theory is. ~ American particle physicist and string theorist David Gross

The “string” in string theory seems somewhat misleading, as the significance is that particle fields have resonances at different frequencies, harmonically interacting with their brethren. Vibe theory sounds more appropriate.

**History**

String theory is 21st-century physics that accidentally found its way into the 20th century. ~ Ed Witten

String theory was presaged by Einstein’s 1907 generalization of photons: a suggestion that solids came as vibrating particles, now termed phonons. Einstein was guessing. The structure of atoms was not discovered until 1911.

Yet Einstein’s phonon serendipity hit the right note. Phonons are relevant to characterizing Bose-Einstein condensate and other exotic thermodynamic phenomena. A phonon is a quasiparticle that represents the excited state which brings electrons together into an entangled Cooper pair.

Phonons were more formally conceptualized by Russian physicist Igor Tamm in 1932 as the particle form of wave/particle fields performing a certain vibration.

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The 1st string theory was proposed in 1926, in the swirl of the quantum revolution, then lost, only to be rediscovered decades later.

Early string theories worked for bosons, leaving fermions out. Bosonic string theory posited 26d. The extra spatial dimensions were necessary to remedy inconsistencies.

In 1968, Italian physicist Gabriele Veneziano was working with the Euler Beta function: an equation used to characterize scattering amplitude. He noticed that it could explain particle reactions involving the strong nuclear force. Others then realized the equation made sense to them when they thought of subatomic particles as connected by little strings, vibrating their very little hearts out.

The concept was controversial. Shortly thereafter, the Standard Model swept aside strings as the great explainer of particle interactions.

But interest in strings abided. Variant models were devised, all constrained to bosonic strings. A major flaw of bosonic string theory was it positing the tachyon: a superluminal particle with imaginary mass.

In 1971, French physicist Pierre Ramond worked a 2D model that included fermions by generalizing the Dirac particle equation into string form. As reality is known to have more than 2 dimensions, Ramond had built a starter kit.

With André Neveu and John Schwarz in tow, Ramond’s concept was extended into a 10d supersymmetry string theory, aka superstring theory.

I think all this superstring stuff is crazy and is in the wrong direction. ~ Richard Feynman

In 1995, American particle theorist Edward Witten, who had been fiddling strings for over a decade, had a vision of unifying the variant quantum field theories. The result was Witten’s M-theory, which postulates 11 dimensions of spacetime: 10 of space and 1 of time. ‘M’ stood for membrane.

M-theory is naturally extensible in the number of dimensions. In M-theory, a single brane string may be a membrane of greater dimensions.

American string theorist Joseph Polchinski and Czech string theorist Petr Horava independently extended M-strings into higher-dimensional objects: D-branes (a Horava term). Among other things, D-brane theory attempts to characterize string endpoints.

D-branes add rich mathematical texture to M-theory, paving the way for constructing more intricate cosmological models with greater explanatory power. Numerous braneworld (brane cosmology) models have emerged.

** Stringy Liquids**

String theory has been derided by partisans for its lack of track record.

String theory cannot give any definite explanations of existing knowledge of the real world and cannot make any definite predictions. ~ American theoretical physicist Daniel Friedan

One experiment tried to simulate the trillion-Kelvin conditions just after the supposed birth of the universe, by smashing gold ions together at 99.99% of the speed of light. Instead of the expected gaseous plasma, a hot quark soup with liquid-like behavior was produced.

Another experiment confined lithium atoms and cooled them to as cold as practically possible: within 1 x 10^{–8} K, barely above absolute zero. The behavior was also liquid-like.

Both these liquids at opposite extremes exhibited collective behavior: flowing with the lowest possible viscosity. String theory successfully modeled these phenomena as strongly coupled particles linked by ripples traveling extra- dimensionally. In contrast, the Standard Model cannot account for these stringy liquids.

A new truth always has to contend with many difficulties. If it were not so, it would have been discovered much sooner. ~ Max Planck

**Planck Units**

All matter originates and exists only by virtue of a force which brings the particle of an atom to vibration and holds this most minute solar system of the atom together. We must assume behind this force the existence of a conscious and intelligent mind. This mind is the matrix of all matter. ~ Max Planck

At the heart of string theory and quantum mechanics lies an inherent ambiguity: the impossibility of probing space when the distance considered heads to the infinitesimally small. The idea of space becomes meaningless when it becomes smaller than what physicists term Planck length.

Under contract to find a way to get the most luminance out of a light bulb using the least energy, German physicist Max Planck originated quantum field theory in 1900. Studying thermal radiation, Planck discovered that energy was always emitted or absorbed in discrete units: quanta. Planck expressed this relation in the simple equation: E = hv, where E is the energy of a wave, v is the frequency of the radiation, and h is a very small number that came to be called the Planck constant (aka Planck’s action quantum), which is 6.626 × 10^{–34} joule/second in meter/kilogram/second units, with just a bit of uncertainty.

Though energy is utterly wavelike, the work of energy only manifests in the discrete amounts specified by Planck’s quantum of action. Phenomenality is confined to granular form – particulate puppets on the strings of waves.

Planck length is a measure derived from Newton’s gravitational constant, the speed of light in a vacuum (c), and Planck’s constant. Planck length is 1.616199 x 10^{-35} meters.

Comparing Planck length to the size of a bacterium is like comparing a bacterium to the size of the known universe. Essentially, Planck length is the theoretical minimal spatial distance.

Planck time is the time required for light in a vacuum to travel a single Planck length; the shortest sprint imaginable, at 5.391 x 10^{–44} seconds. Present physics theories have nothing to say about the universe younger than a Planck time instant. Physicists hold out hope that a theory of quantum gravity might illuminate that moment.

Planck length and Planck time are one system of natural units used in physics, known as Planck units. Planck units serve to mathematically normalize the fundamental quantities of matter, thereby elegantly simplifying algebraic expressions which express properties of elementary particles.

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If matter’s basic nature is of tiny resonances, beyond Planck’s length, the nature of space cannot be probed. Under string theory, space itself appears an emergent property, appearing from spacelessness.

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If quantum physics hasn’t profoundly shocked you, you haven’t understood it yet. ~ Niels Bohr

**Entanglement**

That one body may act upon another at a distance through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it. ~ Isaac Newton

Basic notions in physics depend upon a time continuum: cause preceding effect. A principle of locality must exist for cause and effect to work.

If causality is kicked aside, such as with simultaneous (“spooky”) action at a distance, locality is violated.

Nonlocality is a well-established fact. Quantum entanglement at a distance has repeatedly been demonstrated. In one experiment, a single photon entangled nearly 3,000 atoms.

The fundamental properties of chemistry rely upon entanglement. Solids form, and retain their solidity, via quantum entanglement of the electrons in the material.

Quantum entanglement is a strange and non-intuitive aspect of the quantum theory of matter, which has puzzled and intrigued physicists since the earliest days of the quantum theory. ~ American physicist Leon Balents

Superluminal communication presents a challenge to theoretical physics that has not been resolved. It is a challenge that can never be met by insisting upon the universe as a 4d closed system; the basic axiom which Newton and Einstein were so confident of.

Entanglement demonstrates that time, as well as space, is emergent: constantly coming into being, as contrasted to preexisting and incrementally evolving, as it appears to us.

Space and time will end up being emergent concepts; i.e. they will not be present in the fundamental formulation of the theory and will appear as approximate semiclassical notions in the macroscopic world. This point of view is widely held in the string community. ~ Israeli theoretical physicist Nathan Seiberg

String theory implies countless possible vacuum states; that is, spatial constructs with different properties. From vacuum a spacetime emerges into the universe which we experience. This seeming science fiction is a science fact.

** Entanglement Out of Time**

A practical pointer to time as an emergent property occurs by entangling particles that don’t exist at the same time. Nonlocality can also be nontemporal.

A scheme termed entanglement swapping – chaining entanglement through time between subatomic particle pairs – has been experimentally demonstrated using 4 photons.

First, entangled photons 1 and 2 are created by zapping a special crystal with laser light. The polarization of photon 1 is measured while 1 and 2 are entangled. Photon 1 is destroyed by the measurement.

Then the entangled pair of 3 and 4 are created. Next, an entangling measurement of photons 2 and 3 is made even as it absorbs and destroys them. Finally, the polarization of photon 4 is measured.

Thanks to unavoidable uncertainty, unobserved photons on the fly are simultaneously polarized vertically and horizontally. Measuring a photon collapses its uncertainty wave function such that it will always be found to be either horizontally or vertically polarized.

Even though there is no moment in time when photons 1 and 4 coexist, they show entanglement by their measured polarization matching.

There is no moment in time in which the 2 photons coexist, so you cannot say that the system is entangled at this or that moment. ~ Israeli physicist Hagai Eisenberg