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Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.
(more unsolved problems in physics) In cosmology , the cosmological constant problem or vacuum catastrophe is the substantial disagreement between the observed values of vacuum energy density (the small value of the cosmological constant ) and the much larger theoretical value of zero-point energy suggested by quantum field theory .
For functions in certain classes, the problem of determining: whether two functions are equal, known as the zero-equivalence problem (see Richardson's theorem); [4] the zeroes of a function; whether the indefinite integral of a function is also in the class. [5] Of course, some subclasses of these problems are decidable.
In theoretical physics, the hierarchy problem is the problem concerning the large discrepancy between aspects of the weak force and gravity. [1] There is no scientific consensus on why, for example, the weak force is 10 24 times stronger than gravity .
The sign problem is one of the major unsolved problems in the physics of many-particle systems. It often arises in calculations of the properties of a quantum mechanical system with large number of strongly interacting fermions , or in field theories involving a non-zero density of strongly interacting fermions.
A Fermi problem (or Fermi quiz, Fermi question, Fermi estimate), also known as an order-of-magnitude problem (or order-of-magnitude estimate, order estimation), is an estimation problem in physics or engineering education, designed to teach dimensional analysis or approximation of extreme scientific calculations.
Applying XOR to 010 and 100 obtains 110, that is = =. s = 110 {\displaystyle s=110} can also be verified using input strings 001 and 111 that are both mapped (by f) to the same output string 010. Applying XOR to 001 and 111 obtains 110, that is 001 ⊕ 111 = 110 = s {\displaystyle 001\oplus 111=110=s} .
The three-body problem is a special case of the n-body problem. Historically, the first specific three-body problem to receive extended study was the one involving the Earth, the Moon, and the Sun. [2] In an extended modern sense, a three-body problem is any problem in classical mechanics or quantum mechanics that models the motion of three ...