To the best of my understanding, the Pauli principle is a mathematical consequence of what we understand by a Fermion. Whether all particles must be fermions or bosons depends on theory, and perhaps on experiment. But if a particle fails to satisfy the exclusion principle, then it is not a Fermion. Similar comments might apply, say, to attempt to detect deviations from Pythgoras' theorem. A possible violation would mean either that the triangle was not right-angled, or that Geometry was not Euclidean.

The answer is No. What should be understood is that any experiment will give a finite answer, associated with systematic and statistical errors. The issue is, whether, a result is compatible with what is expected, to a given accuracy. Indeed, this is the case. Fiurthermore, if the Pauli exclusion principle *were* violated in this experiment, this should have appeared, more strongly, eventually, in other experiments-which isn't the case.

In addition, knowing this, it's useful to use such experiments for calibration purposes: since we do expect that the Pauli exclusion principle to hold, to experimental accuracy, we can test the apparatus, that it does work properly.

Dear Victor,

"So far no "- is the answer.

But any principle, however useful cannot be absolute. It may be in physics or elsewhere, though usually it may be considered inviolable, it may have violations in certain special situations.

For example, when in high energy experiments super-symmetry manifests and fermions and bosons combine in one multiplet, then Pauli Principle may be violated, since the classification of particles into Bosons and Fermions would no longer be valid at that energy scale.

Neutrosophy logic does not add much. But it serves to shake a bit our confidence in well established doctrines, whose fallibility we forget habitually.

Regards,

Rajat

No, supersymmetry does not imply violation of the Pauli exclusion principle. 

To the best of my understanding, the Pauli principle is a mathematical consequence of what we understand by a Fermion. Whether all particles must be fermions or bosons depends on theory, and perhaps on experiment. But if a particle fails to satisfy the exclusion principle, then it is not a Fermion. Similar comments might apply, say, to attempt to detect deviations from Pythgoras' theorem. A possible violation would mean either that the triangle was not right-angled, or that Geometry was not Euclidean.

A nice article is by A. S. Wightman, http://ejde.math.txstate.edu/conf-proc/04/w1/wightman.pdf, since the issue is spin-statistics. Once more, what's important is that, if such a violation had occurred, inevitably it would have had consequences elsewhere that would have been observed. 

The Pauli principle, as recalled in Wghtman's article can't be proved within non-relativistic quantum mechanics-it requires Lorentz invariance. (The spin-statistics theorem is distinct from the CPT theorem.) All this, and more,  is explained very clearly in Wightman's article. But these are, of course, mathematical statements. The interesting part is that there exist physical systems, whose description is, inevitably, approximate, but, nonetheless, does verify the assumptions of these theorems, therefore their conclusions. So it does make sense to ask, whether the description of physical systems, upon refinement, will continue to satisfy the assumptions of the theorems and how this can be tested experimentally. The latter, indeed, can serve as a calibration of the experiments.

@Rajat, Stam, Luiz: thanks for your answers. Btw, i just found a paper suggesting violation of PEP may be possible becauee of decrease of entropy (http://arxiv.org/pdf/0810.0313.pdf). What do you think? Thanks

http://arxiv.org/pdf/0810.0313.pdf

It's useful to read Wightman's paper. The spin-statistics theorem has certain assumptions-if these don't hold, the conclusion doesn't hold. In particular, Lorentz invariance is assumed.In the situation described in the paper  linked to, the situation isn't invariant under Lorentz transformations (which, in particular, include time translations-among other things, it describes a situation at finite temperature, i.e. there is a preferred value for the energy). Therefore the spin-statistics theorem wouldn't be expected to hold. So it wouldn't be a violation, given that it isn't expected to hold in such a situation at all. To show violation of any proposition, it's necessary to produce a situation that satisfies the assumptions, but not the conclusion.

Victor,

Wang proposes in his paper that the existence of internal interactions is a necessary condition of entropy decrease in isolated systems. Unfortunately his examples do not cocern strictly isolated systems.

As a geometrical/topological  property in configuration space, the Pauli exclusion principle is a property of a space with no curvature or torsion nor singular point (think of the discussion on anyons by Leinaas and  Myrheim  as two body dynamics on a conical surface)

A violation could reveal this property. As the curvature of physical space is very tiny ,at the atomic or molecular level where the principle acts, this kind of violation and the associated symmetry breaking is expected to be hidden by many other effects. There are experiment that expect to find symmetry violations  , the remaining problem beiing to assigne preciselly the violation to a definite physical law.

No, a violation couldn't reveal this, because spacetime curvature means that Lorentz invariance isn't a global symmetry, which is an *assumption* of the spin-statistics theorem. (If spacetime curvature  is relevant then something more is needed and it is known how to do this, namely how to define spinors in curved spacetime-and when this isn't possible.)

Anyons don't violate the spin-statistics theorem, because its assumptions don't apply to them.

Once more, to show a violation it's necessary to look for situations where the assumptions are satisfied, not where they are not. 

I agree with the preceeding answer. The point I discussed was detection of an apparent violation.

An example of such a check of the conclusions may be found here: http://arxiv.org/abs/cond-mat/0501665 ``Consequences of the Pauli exclusion principle for the Bose-Einstein condensation of atoms and excitons''

i think this principle is not valid in Quarks. ( I have to re-check...)... somewhere in Feynman lectures/talks, this is mentioned. please clarify...

Of course it is-that's how color got introduced in the quark model. 

No; quarks are described by QCD-as  spin 1/2 particles. The consequences of this description have been abundantly confirmed by experiment.In four spacetime dimensions spin 1/2 particles  are fermions. 

It is possible to parametrize the same physical object and phenomenon in many different ways. Under the assumptions of locality, Lorentz invariance and a positive definite Hamiltonian, the description of quarks as spin 1/2 particles (which has been experimentally tested through polarized scattering experiments)   is QCD.  And QCD is a description of weakly coupled fields (thanks to the property of asymptotic freedom) for which a particle interpretation is appropriate.This implies that quarks are fermions. It's useful to distinguish words and symbols that express equivalent physical descriptions, from inequivalent physical descriptions. One is metaphysics, for which there isn't any useful discussion; the other is physics. 

Gluons have been observed as jets unambiguously since the late 1970s. This was made possible thanks to the calculations of perturbative QCD, rendered effective thanks to asymptotic freedom,  and experimental ingenuity. One doesn't make sense without the other. Sensible calculations have been done for more than forty years to a precision such that the Standard Model is now complete  at the LHC and is the background for observing new effects. It wouldn't have been possible to detect the Higgs, without extraordinary control of the QCD backgrounds. The régime of perturbative QCD is under control quantitatively and qualitatively and non-perurbative features are now becoming quantitatively precise from lattice calculations of flavor physics. And all this is taught, properly, to students since decades. Many of the metaphysical assertions that are just words are, just a sign of history, that has, since been properly understood and the correct way to think and calculate is available in countless schools and textbooks. This understanding is the foundation of the new search strategies at the LHC, without which they couldn't have been developed. Historical timelines  are  one thing-current technical understanding and practice another. One doesn't teach all the wrong ways people tried to understand a concept, once the right way has been understood-unless it's for a history of science course.

Claiming mathematical rigor isn't the same as practicing it. A basic aspect of physics-and mathematics-is knowing what a good approximation is. And how to distinguish technical tools that are but one way to describe a problem, from the problem itself, that can be described by many other tools. Not all tools are the most useful for all problems. And one doesn't get extra marks for solving a problem in some particular way-but by solving it in a controlled way.  The statements about perturbative QCD and its experimental tests can be given  a controlled quantitative foundation and that's what matters. It is possible to learn and understand the limits of the calculation and the limits of the experiment in a  purely impersonal way.  Same for lattice calculations. Their results mean something specific and this can be controlled. Once more, popular accounts aren't useful for technical matters and one shouldn't confuse sociological aspects of a field with the technical aspects. (Incidentally, QED-rather, since forty years now, the electroweak sector of the Standard Model-is different from QCD, in a very important way: the latter is weakly coupled at short distances, the former at long distances. This isn't a sociological decision, but the result of a well-defined calculation and has consequences that have been extensively tested experimentally.)

Pauli exclusion principle will NEVER be violated by any physical object. There will be a finite space between any two object even at angstrom level. In material, this is called lattice parameter. No matter how much you apply the force, lattice parameter or space between any two object will never be perfect zero. Space is extremely repulsive at nano-scale. Due to this repulsion, normal force develops between any two physical surface. The day Pauli exclusion principle breaks, whole QM will be collapsed. Nothing will exist in nature.