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Dmitri Diakonov

Publications and source records attributed to Dmitri Diakonov.

At least 37 records · Page 2Linked to original sources
arXiv2007

Confining ensemble of dyons

We construct the integration measure over the moduli space of an arbitrary number of N kinds of dyons of the pure SU(N) gauge theory at finite temperatures. The ensemble of dyons governed by the measure is mathematically described by a (supersymmetric) quantum field theory that is exactly solvable and is remarkable for a number of striking features: 1) The free energy has the minimum corresponding to the zero average Polyakov line, as expected in the confining phase; 2)The correlation function of two Polyakov lines exhibits a linear potential between static quarks in any N-ality non-zero representation, with a calculable string tension roughly independent of temperature; 3) The average spatial Wilson loop falls off exponentially with its area and the same string tension; 4) At a critical temperature the ensemble of dyons rearranges and de-confines; 5)The estimated ratio of the critical temperature to the square root of the string tension is in excellent agreement with the lattice data.

hep-th↗
arXiv2006

To see the exotic Theta^+ baryon from interference

Since all couplings of the exotic $Θ^+$ baryon to normal hadrons seem to be small it is hard to reveal it in standard resonance searching. We suggest to look for the $Θ^+$ production in interference with a known resonance yielding the same final state but having a high production rate. The interference process is linear in the $Θ^+$ couplings whereas the non-interference process is quadratic. That gives an obvious gain if the couplings are small. Moreover, employing the peculiar oscillating nature of the interference processes one can reduce considerably the parasitic background and determine the $Θ^+$ resonance parameters.

hep-ph↗
arXiv2006

The narrow pentaquark

The experimental status of the pentaquark searches is briefly reviewed. Recent null results by the CLAS collaboration are commented, and new strong evidence of a very narrow Theta+ resonance by the DIANA collaboration is presented. On the theory side, I revisit the argument against the existence of the pentaquark -- that of Callan and Klebanov -- and show that actually a strong resonance is predicted in that approach, however its width is grossly overestimated. A recent calculation gives 2 MeV for the pentaquark width, and this number is probably still an upper bound.

hep-ph↗
arXiv2005

Estimate of the Theta+ width in the Relativistic Mean Field Approximation

In the Relativistic Mean Field Approximation three quarks in baryons from the lowest octet and the decuplet are bound by the self-consistent chiral field, and there are additional quark-antiquark pairs whose wave function also follows from the mean field. We present a generating functional for the 3-quark, 5-quark, 7-quark ... wave functions inside the octet, decuplet and antidecuplet baryons treated in a universal and compact way. The 3-quark components have the SU(6)-symmetric wave functions but with specific relativistic corrections which are generally not small. In particular, the normalization of the 5-quark component in the nucleon is about 50% of the 3-quark component. We give explicitly the 5-quark wave functions of the nucleon and of the exotic Theta+. We develop a formalism how to compute observables related to the 3- and 5-quark Fock components of baryons, and apply it to estimate the Theta+ width which turns out to be very small, 2-4 MeV, although with a large uncertainty.

hep-ph↗
arXiv2005

SU(N) caloron measure and its relation to instantons

Calorons of the SU(N) gauge group with non-trivial holonomy, i.e. periodic instantons with arbitrary eigenvalues of the Polyakov line at spatial infinity, can be viewed as composed of N Bogomolnyi--Prasad--Sommerfeld (BPS) monopoles or dyons. Using the metric of the caloron moduli space found previously we compute the integration measure over caloron collective coordinates in terms of the constituent monopole positions and their U(1) phases. In the limit of small separations between dyons and/or trivial holonomy, calorons reduce locally to the standard instantons whose traditional collective coordinates are the instanton center, size and orientation in the color space. We show that in this limit the instanton collective coordinates can be explicitly written through dyons positions and phases, and that the N-dyon measure coincides exactly with the standard instanton one.

hep-th↗
arXiv2004

Chiral symmetry and pentaquarks

Spontaneous chiral symmetry breaking, mesons and baryons are illustrated in the language of the Dirac theory. Various forces acting between quarks inside baryons are discussed. I explain why the naive quark models typically overestimate pentaquark masses by some 500 MeV and why in the fully relativistic approach to baryons pentaquarks turn out to be light. I discuss briefly why it can be easier to produce pentaquarks at low than at high energies.

hep-ph↗
arXiv2004

Baryons as Fock states of 3,5,... quarks

We present a generating functional producing quark wave functions of all Fock states in the octet, decuplet and antidecuplet baryons in the mean field approximation, both in the rest and infinite momentum frames. In particular, for the usual octet and decuplet baryons we get the SU(6)-symmetric wave functions for their 3-quark component but with specific corrections from relativism and from additional quark-antiquark pairs. For the exotic antidecuplet baryons we obtain the 5-quark wave function.

hep-ph↗
arXiv2004

Gauge invariant effective action for the Polyakov line in the SU(N) Yang--Mills theory at high temperatures

We integrate out fast varying quantum fluctuations around static A_4 and A_i fields for the SU(N) gauge group. By assuming that the gluon fields are slowly varying but allowing for an arbitrary amplitude of A_4 we obtain two variants of the effective high-temperature theory for the Polyakov line. One is the effective action for the gauge-invariant eigenvalues of the Polyakov line, and it is explicitly Z(N) symmetric. The other is the effective action for the Polyakov line itself as an element of the SU(N). In this case the theory necessarily includes the spatial components A_i to ensure its gauge invariance under spatial gauge transformations. We derive the 1-loop effective action in the `electric' and `magnetic' sectors, summing up all powers of A_4.

hep-ph↗
arXiv2004

Quark structure of chiral solitons

There is a prejudice that the chiral soliton model of baryons is something orthogonal to the good old constituent quark models. In fact, it is the opposite: the spontaneous chiral symmetry breaking in strong interactions explains the appearance of massive constituent quarks of small size thus justifying the constituent quark models, in the first place. Chiral symmetry ensures that constituent quarks interact very strongly with the pseudoscalar fields. The ``chiral soliton'' is another word for the chiral field binding constituent quarks. We show how the old SU(6) quark wave functions follow from the ``soliton'', however, with computable relativistic corrections and additional quark-antiquark pairs. We also find the 5-quark wave function of the exotic baryon Theta+.

hep-ph↗
arXiv2004

Quantum weights of monopoles and calorons with non-trivial holonomy

The functional determinant is computed exactly for quantum oscillations about periodic instantons with non-trivial values of the Polyakov line at spatial infinity (or holonomy). Such instantons can be viewed as composed of the Bogomolnyi--Prasad--Sommerfeld (BPS) monopoles or dyons. We find the weight or the probability with which dyons occur in the pure Yang--Mills partition function. It turns out that dyons experience quantum interactions having the familiar "linear plus Coulomb" form but with the "string tension'' depending on the holonomy. We present an argument that at temperatures below the critical one computed from Lambda_QCD, trivial holonomy becomes unstable, with instantons ``ionizing'' into separate dyons. It may serve as a microscopic mechanism of the confinement-deconfinement phase transition.

hep-ph↗
arXiv2004

From pions to pentaquarks

I overview the physical picture of QCD at low energies that has led to the prediction of a narrow exotic baryon Theta^+ which cannot be made of three quarks. The very narrow width of the Theta^+ and a possible reason why it is seen in low- but not in high-energy experiments are briefly discussed.

hep-ph↗
arXiv2004

Comment on the Theta+ width and mass

We discuss the relatively low mass and narrow width prediction for the exotic baryon Theta+, and comment on recent statements by R.L. Jaffe on the subject. We reaffirm that a narrow width of 3.6-11.2 MeV follows from the equations of our 1997 paper.

hep-ph↗
arXiv2004

Quantum weights of dyons and of instantons with non-trivial holonomy

We calculate exactly functional determinants for quantum oscillations about periodic instantons with non-trivial value of the Polyakov line at spatial infinity. Hence, we find the weight or the probability with which calorons with non-trivial holonomy occur in the Yang--Mills partition function. The weight depends on the value of the holonomy, the temperature, Lambda_QCD, and the separation between the BPS monopoles (or dyons) which constitute the periodic instanton. At large separation between constituent dyons, the quantum measure factorizes into a product of individual dyon measures, times a definite interaction energy. We present an argument that at temperatures below a critical one related to Lambda_QCD, trivial holonomy is unstable, and that calorons ``ionize'' into separate dyons.

hep-th↗
arXiv2003

A heretical view on linear Regge trajectories

We discuss a possibility that linear Regge trajectories originate not from gluonic strings connecting quarks, as it is usually assumed, but from pion excitations of light hadrons. From this point of view, at large angular momenta both baryons and mesons lying on linear Regge trajectories are slowly rotating thick strings of pion field, giving rise to a universal slope computable from the pion decay constant. The finite resonance widths are mainly due to the semiclassical radiation of pion fields by the rotating elongated chiral solitons. Quantum fluctuations about the soliton determine a string theory which, being quantized, gives the quantum numbers for Regge trajectories.

hep-ph↗
arXiv2003

Where are the missing members of the baryon antidecuplet?

We analyze what consequences has the observation of exotic pentaquark baryons on the location of the non-exotic baryons belonging to the antidecuplet. We suggest that there must be a new nucleon state at 1650-1690 MeV and a new Sigma baryon at 1760-1810 MeV.

hep-ph↗
arXiv2003

Exotic baryon multiplets at large number of colours

We generalize the usual octet, decuplet and exotic antidecuplet and higher baryon multiplets to any number of colours Nc. We show that the multiplets fall into a sequence of bands with O(1/Nc) splittings inside the band and O(1)splittings between the bands characterized by "exoticness", that is the number of extra quark-antiquark pairs needed to compose the multiplet. Each time one adds a pair the baryon mass is increased by the same constant which can be interpreted as a mass of a quark-antiquark pair. At the same time, we prove that masses of exotic rotational multiplets are reliably determined at large Nc from collective quantization of chiral solitons.

hep-ph↗
arXiv2003

Instantons at work

The aim of this review is to demonstrate that there exists a coherent picture of strong interactions, based on instantons. Starting from the first principles of QCD - via the microscopic mechanism of spontaneous chiral symmetry breaking - one arrives to a quantitative description of light hadron properties, with no fitting parameters. The discussion of the importance of instanton-induced interactions in soft high-energy scattering is new.

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