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kcajrenreb
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What makes some strings have mass, and others none? (eg. graviton vs. electron)
Not really. A string with no vibration at all actually has a NEGATIVE mass squared. This perhaps counterintuitive fact can only be understood through quantum mechanics of strings. In supesymmetric string theory such a no-vibration mode of string is unphysical, so the next lowest (first physical) mode of vibration is massless.kcajrenreb said:So a massless string has no vibration at all?
Right.kcajrenreb said:Yeah, a string with negative mass squared is a tachyon, right? And supersymmetry was made to avoid that problem, correct?
The concept of a massless string refers to a theoretical string that has no mass, meaning it has zero weight. In physics, mass is a measure of the amount of matter in an object, so a massless string would have no physical substance or particles that make it up. It is often used as a simplifying assumption in theoretical models or calculations.
No, a string in the real world cannot be truly massless. All physical objects, including strings, have some amount of mass. The concept of a massless string is purely theoretical and is used as a simplifying assumption for certain calculations and models.
The mass of a string can be affected by various factors, including its length, thickness, and the material it is made of. For example, a longer string will have more mass than a shorter string made of the same material. Additionally, denser materials will have a greater mass than less dense materials.
The mass of a string can impact its physical properties in several ways. A heavier string will be able to withstand more tension and is less likely to break than a lighter string. Additionally, the mass of a string can affect its vibration and resonance properties, which is important for instruments like guitars and violins.
While it is not possible to completely eliminate the mass of a string, it is possible to reduce it. This can be achieved by using lighter materials or thinner strings. However, there will always be some amount of mass present, as even the smallest particles have some mass. The concept of a massless string is purely theoretical and cannot be achieved in the real world.