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Dmitri Diakonov

Publications and source records attributed to Dmitri Diakonov.

At least 55 records · Page 3Linked to original sources
arXiv2003

Center-Vortex Solutions of the Yang-Mills Effective Action in Three and Four Dimensions

We calculate the one-loop effective action of the SU(2) Yang-Mills theory for center-vortex configurations, both in 3d and 4d. We find that in both cases there are minima of the effective action, corresponding to vortices of the transverse size approximately 4/g_3^2 and 1.7/Lambda_MS, respectively. The values of the effective actions at the minima are negative, suggesting that the Euclidian vacuum may be unstable with respect to creation of vortices.

hep-lat↗
arXiv2002

Yang-Mills theory in terms of gauge invariant dual variables

Quantum Yang-Mills theory and the Wilson loop can be rewritten identically in terms of local gauge-invariant variables being directly related to the metric of the dual space. In this formulation, one reveals a hidden high local symmetry of the Yang-Mills theory, which mixes up fields with spins up to J=N for the SU(N) gauge group. In the simplest case of the SU(2) group the dual space seems to tend to the de Sitter space in the infrared region. This observation suggests a new mechanism of gauge-invariant mass generation in the Yang-Mills theory.

hep-th↗
arXiv2002

Center vortices and k-strings

The vortex contribution to the $k$-string tensions is computed for SU($N$) gauge theories. We deduce the surface densities needed to reproduce the sine scaling and the Casimir scaling formulae, recently obtained from numerical simulations on the lattice. We find that such densities need to grow linearly in $N$, which in turn suggests that the vortex scenario can hardly reproduce the physics of confinement at large $N$.

hep-lat↗
arXiv2002

Instantons and baryon dynamics

I explain how instantons break chiral symmetry and how do they bind quarks in baryons. The confining potential is possibly irrelevant for the task.

hep-ph↗
arXiv2002

Yang-Mills theory as a quantum gravity with `aether'

Quantum Yang-Mills theory can be rewritten in terms of gauge-invariant variables: it has the form of the so-called BF gravity, with an additional `aether' term. The BF gravity based on the gauge group SU(N) is actually a theory of high spin fields (up to J=N) with high local symmetry mixing up fields with different spins -- like in supergravity but without fermions. At N going to infinity one gets a theory with an infinite tower of spins related by local symmetry, similar to what one has in string theory. We, thus, outline a way to derive string theory from a local Yang-Mills theory in the large N limit.

hep-th↗
arXiv2001

Loop structure of the lowest Bloch band for a Bose-Einstein condensate

We investigate analytically and numerically Bloch waves for a Bose--Einstein condensate in a sinusoidal external potential. At low densities the dependence of the energy on the quasimomentum is similar to that for a single particle, but at densities greater than a critical one the lowest band becomes triple-valued near the boundary of the first Brillouin zone and develops the structure characteristic of the swallow-tail catastrophe. We comment on the experimental consequences of this behavior.

cond-mat↗
arXiv2000

Gauge-invariant formulation of the d=3 Yang-Mills theory

We write down the Yang-Mills partition function and the average Wilson loop in terms of local gauge-invariant variables being the six components of the metric tensor of dual space. The Wilson loop becomes the trace of the parallel transporter in curved space, else called the gravitational holonomy. We show that the external coordinates mapping the 3d curved space into a flat 6d space play the role of glueball fields, and there is a natural mechanism for the mass gap generation.

hep-th↗
arXiv2000

Nucleons as chiral solitons

In the limit of large number of colors N the nucleon consisting of N quarks is heavy, and one can treat it semiclassically, like the large-Z Thomas--Fermi atom. The role of the semiclassical field binding the quarks in the nucleon is played by the pion or chiral field; its saddle-point distribution inside the nucleon is called the chiral soliton. The old Skyrme model for this soliton is an over-simplification. One can do far better by exploiting a realistic and theoretically-motivated effective chiral lagrangian presented in this paper. As a result one gets not only the static characteristics of the nucleon in a fair accordance with the experiment (such as masses, magnetic moments and formfactors) but also much more detailed dynamic characteristics like numerous parton distributions. We review the foundations of the Chiral Quark-Soliton Model of the nucleon as well as its recent applications to parton distributions, including the recently introduced `skewed' distributions, and to the nucleon wave function on the light cone.

hep-ph↗
arXiv2000

On the Non-Abelian Stokes Theorem

We present the non-Abelian Stokes theorem for the Wilson loop in various forms and discuss its meaning. Its validity has been recently questioned by Faber, Ivanov, Troitskaya and Zach. We demonstrate that all points of their criticism are based on mistakes in mathematics. Finally, we derive a variant of our formula for the Wilson loop in lattice regularization.

hep-lat↗
arXiv2000

Non-Abelian Stokes Theorems in Yang-Mills and Gravity Theories

We recall the non-Abelian Stokes theorem for the Wilson loop in the Yang-Mills theory and discuss its meaning. Then we move to `gravitational Wilson loops', i.e. to holonomies in curved d=2,3,4 spaces and derive non-Abelian Stokes theorems for these quantities as well, which are similar to our formula in the Yang-Mills theory. In particular we derive an elegant formula for the holonomy in the case of a constant-curvature background in three dimensions and a formula for small-area loops in any number of dimensions.

hep-th↗
arXiv2000

Yang-Mills Theory in Three Dimensions as Quantum Gravity Theory

We perform the dual transformation of the Yang-Mills theory in d=3 dimensions using the Wilson action on the cubic lattice. The dual lattice is made of tetrahedra triangulating a 3-dimensional curved manifold but embedded into a flat 6-dimensional space (for the SU(2) gauge group). In the continuum limit the theory can be reformulated in terms of 6-component gauge-invariant scalar fields having the meaning of the external coordinates of the dual lattice sites. These 6-component fields induce a metric and a curvature of the 3-dimensional dual colour space. The Yang-Mills theory can be identically rewritten as a quantum gravity theory with the Einstein-Hilbert action but purely imaginary Newton constant, plus a homogeneous `matter' term. Interestingly, the theory can be formulated in a gauge-invariant and local form without explicit colour degrees of freedom.

hep-th↗
arXiv1999

Vortex solution in 2+1 dimensional Yang-Mills theory at high temperatures

At high temperatures the A_0 component of the Yang--Mills field plays the role of the Higgs field, and the 1-loop potential V(A_0) plays the role of the Higgs potential. We find a new stable vortex solution of the Abrikosov-Nielsen-Olesen type, and discuss its properties and possible implications.

hep-th↗
arXiv1999

Chiral Symmetry Breaking and Color Superconductivity in the Instanton Picture

The instanton approach to spontaneous chiral symmetry breaking is reviewed, with emphasis on the connection to chiral random matrix theory. We extend the approach to discuss the finite density, zero-temperature behaviour of quark matter. Since the instanton-induced interactions are attractive in both $\bar{q}q$ and $qq$ channels, a competition ensues between phases of matter with condensation in either or both. It results in chiral symmetry restoration due to the onset of diquark condensation, a `colour superconductor', at finite density.

hep-ph↗
arXiv1999

Potential energy of Yang-Mills vortices in three and four dimensions

We calculate the energy of a Yang-Mills vortex as function of its magnetic flux or, else, of the Wilson loop surrounding the vortex center. The calculation is performed in the 1-loop approximation. A parallel with a potential as function of the Polyakov line at nonzero temperatures is drawn. We find that quantized Z(2) vortices are dynamically preferred though vortices with arbitrary fluxes cannot be ruled out.

hep-th↗
arXiv1999

To what distances do we know the confining potential?

We argue that asymptotically linear static potential is built in into the common procedure of extracting it from lattice Wilson loop measurements. To illustrate the point, we extract the potential by the standard lattice method in a model vacuum made of instantons. A beautiful infinitely rising linear potential is obtained in the case where the true potential is actually flattening. We argue that the flux tube formation might be also an artifact of the lattice procedure and not necessarily a measured physical effect. We conclude that at present the rising potential is known for sure up to no more than about 0.7 fm. It may explain why no screening has been clearly observed so far for adjoint sources and for fundamental sources but with dynamical fermions. Finally, we speculate on how confinement could be achieved even if the static potential in the pure glue theory is not infinitely rising.

hep-lat↗
arXiv1998

Trying to understand confinement in the Schroedinger picture

We study the gauge-invariant gaussian ansatz for the vacuum wave functional and show that it potentially possesses many desirable features of the Yang--Mills theory, like asymptotic freedom, mass generation through the transmutation of dimensions and a linear potential between static quarks. We point out that these (and other) features can be studied in a systematic way by combining perturbative and 1/n expansions. Contrary to the euclidean approach, confinement can be easily formulated and easily built in, if not derived, in the variational Schroedinger approach.

hep-th↗