منابع مشابه
Positivity constraints in QCD
The density matrix positivity is a natural counterpart of unitarity. The resulting constraints for various parton distribution and correlations are considered. Their compatibility with leading order QCD evolution is guaranteed by the probabilistic interpretation of the latter. In the case of non-forward distributions the positivity constraints naturally imply the symmetric form of the evolution...
متن کاملDiagnosing and responding to violations in the positivity assumption.
The assumption of positivity or experimental treatment assignment requires that observed treatment levels vary within confounder strata. This article discusses the positivity assumption in the context of assessing model and parameter-specific identifiability of causal effects. Positivity violations occur when certain subgroups in a sample rarely or never receive some treatments of interest. The...
متن کاملPositivity of Qcd at Asymptotic Density
In this talk, I try to show that the sign problem of dense QCD is due to modes whose frequency is higher than the chemical potential. An effective theory of quasi-quarks near the Fermi surface has a positive measure in the leading order. The higherorder corrections make the measure complex, but they are suppressed as long as the chemical potential is sufficiently larger than ΛQCD. As a conseque...
متن کاملMassless mode and positivity violation in hot QCD.
We calculate the quark self-energy at one-loop level at high temperature, taking into account contributions from both the (chromo)electric scale gT and the (chromo)magnetic scale g^{2}T. While reproducing standard massive excitations due to the electric scale, we uncover a novel massless excitation ascribable to the magnetic scale. The residue of this massless excitation is nonpositive at all t...
متن کاملOn some positivity properties of the interquark potential in QCD.
We argue that the Fourier transform of the exponential e(-betaV(R)) of the static interquark potential in QCD is positive. It has been shown by Lieb some time ago that this property allows in the same limit of static, spin independent potential, to prove a certain mass relation between baryons with different quark flavors.
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ژورنال
عنوان ژورنال: Modern Physics Letters A
سال: 2013
ISSN: 0217-7323,1793-6632
DOI: 10.1142/s0217732313300358