arXiv subjects

Ariel R. Zhitnitsky

Publications and source records attributed to Ariel R. Zhitnitsky.

At least 73 records · Page 4Linked to original sources

arXiv2003

Vortons in the SO(5) model of high temperature superconductivity

It has been shown that superconducting vortices with antiferromagnetic cores arise within Zhang's SO(5) model of high temperature supercondictivity. Similar phenomena where the symmetry is not restored in the core of the vortex was discussed by Witten in the case of cosmic strings. It was also suggested that such strings can form stable vortons, which are closed loops of such vortices. Motivated by this analogy, in following we will show that loops of such vortices in the SO(5) model of high T_c superconductivity can exist as classically stable objects, stabilized by the presence of conserved charges trapped on the vortex core. These objects carry angular momentum which counteracts the effect of the string tension that causes the loops to shrink. The existence of such quasiparticles, which are called vortons, could be interesting for the physics of high temperature superconductors. We also speculate that the phase transition between superconducting and antiferromagnetic phases at zero external magnetic field when the doping parameter changes is associated with vortons.

cond-mat.supr-con↗

arXiv2002

Superconducting K strings in high density QCD

Recently it has been argued that the ground state of high density QCD is likely be a combination of the CFL-phase along with condensation of the K^0 field. This state spontaneously breaks a global U(1)_Y symmetry, therefore one would expect the formation of U(1)_Y global strings. We discuss the core structure of these strings and demonstrate that under some conditions the global U(1)_Y symmetry may not be restored inside the string, in contrast with the standard expectations. Instead, K^+ condensation occurs inside the core of the string if a relevant parameter \cosθ_K = \mkzero^2/μ_eff^2 is larger than some critical value θ_K > θ_crit. If this phenomenon happens, the U(1)_Y strings become superconducting and may considerably influence the magnetic properties of dense quark matter, in particular in neutron stars.

hep-ph↗

arXiv2002

Dark Matter as Dense Color Superconductor

We discuss a novel cold dark matter candidate which is formed from the ordinary quarks during the QCD phase transition when the axion domain wall undergoes an unchecked collapse due to the tension in the wall. If a large number of quarks is trapped inside the bulk of a closed axion domain wall, the collapse stops due to the internal Fermi pressure. In this case the system in the bulk, may reach the critical density when it undergoes a phase transition to a color superconducting phase with the ground state being the quark condensate, similar to BCS theory. If this happens, the new state of matter representing the diquark condensate with a large baryon number B > 10^{20} becomes a stable soliton-like configuration. Consequently, it may serve as a novel cold dark matter candidate.

astro-ph↗

arXiv2001

Domain Walls in QCD

QCD was shown to have a nontrivial vacuum structure due to the topology of the theta = theta+2*pi*n parameter. As a result of this nontrivial topology, in the large N_c limit, quasi-stable QCD domain walls appear, characterized by a transition in the singlet eta' field. We discuss the physics of these QCD domain walls as well as related axion domain walls and we present a new type of axion wall which also contains an eta' transition. We argue that these domain walls are topologically stable in the limit N_c->infinity and classically stable for large but finite N_c, however, they can decay through a tunneling process. We argue that the qualitative features of these QCD domain walls -- namely their classical stability -- persist to the realistic case of N_c=3 and that it is at least possible that their lifetime could be macroscopically large. If it is, then QCD domain walls could play an important role in the evolution of early universe and may be detectable in energetic collisions such as those at the Relativistic Heavy Ion Collider (RHIC).

hep-ph↗

arXiv2001

Global Strings in High Density QCD

We show that several types of global strings occur in colour superconducting quark matter due to the spontaneous violation of relevant U(1) symmetries. These include the baryon U(1)_B, and approximate axial U(1)_A symmetries as well as an approximate U(1)_S arising from kaon condensation. We discuss some general properties of these strings and their interactions. In particular, we demonstrate that the U(1)_A strings behave as superconducting strings. We draw some parallels between these strings and global cosmological strings and discuss some possible implications of these strings to the physics in neutron star cores.

hep-ph↗

arXiv2001

Primordial Galactic Magnetic Fields: An Application of QCD Domain Walls

We present a mechanism for generating primordial magnetic fields with large correlation lengths on the order of 100 kpc today. The mechanism is based on recently conjectured QCD domain walls or similar CP violating domain walls with QCD scale structure. Such domain walls align the electric and magnetic dipole moments of the nucleons shortly after the QCD phase transition, producing electromagnetic fields correlated along the domain walls. Through the Kibble mechanism, the domain walls attain Hubble-scale correlations which they transfer to the aligned electromagnetic fields. Due to the CP violation, the Hubble-scale walls produce helical (non-zero Chern-Simons) magnetohydrodynamic turbulence which then undergoes an inverse cascade, allowing the correlation lengths to grow to 100 kpc today. We present an estimate the magnitude of the generated electromagnetic fields in terms of the QCD parameters. We also discuss some other unexplained astrophysical phenomena which may be related to this mechanism. In particular, we discuss the relation between primordial magnetic fields and the Greisen-Zatsepin-Kuzmin (GZK) cutoff violations. We also outline how, by creating inhomogeneities in the nucleon density, QCD domain walls may lead to inhomogeneous big bang nucleosynthesis (IBBN) explaining the Omega_B excess recently measured through cosmic microwave background (CMB) distortions.

hep-ph↗

arXiv2001

Primordial galactic magnetic fields from domain walls at the QCD phase transition

We propose a mechanism to generate large-scale magnetic fields with correlation lengths of 100 kpc. Domain walls with QCD scale internal structure form and coalesce obtaining Hubble scale correlations and align nucleon spins. Due to strong CP violation, nucleons in these walls have anomalous electric and magnetic dipole moments and thus the walls are ferromagnetic. This induces electromagnetic fields with Hubble size correlations. The same CP violation also induces a maximal helicity (Chern-Simons) correlated through the Hubble volume which supports an inverse cascade allowing the initial correlations to grow to 100 kpc today. We estimate the generated electromagnetic fields in terms of the QCD parameters and discuss the effects of the resulting fields.

hep-ph↗

arXiv2000

Primordial Galactic Magnetic Fields from the QCD Phase Transition

In this paper, we propose a mechanism to generate large-scale magnetic fields with correlations lengths of 100 kpc. Domain walls with QCD scale internal structure form and coalesce obtaining Hubble size correlations and align nucleon spins. Due to strong CP violation, nucleons in these walls have anomalous electric and magnetic dipole moments and thus the walls are ferromagnetic. This induces electromagnetic fields with Hubble size correlations. The same CP violation also induces maximal helicity (Chern-Simons) correlated through the Hubble volume which supports an "inverse cascade" allowing the initial correlations to grow to 100 kpc today. We estimate the generated electromagnetic fields in terms of the QCD parameters and discuss the effects of the resulting fields.

hep-ph↗

arXiv2000

Coulomb Gas Representation of Low Energy QCD

A novel Coulomb gas (CG) description of low energy $QCD_4$, based on the dual transformation of the QCD effective chiral Lagrangian, is constructed. The CG is found to contain several species of charges, one of which is fractionally charged and can be interpreted as instanton-quarks. The creation operator which inserts a pseudo-particle in the CG picture is explicitly constructed and demonstrated to have a non-zero vacuum expectation value. The Wilson loop operator as well as the creation operator for the domain wall in the CG representation is also constructed.

hep-ph↗

arXiv1999

Monopoles and Coulomb Gas Representation of the QCD Effective Lagrangian

A novel Coulomb gas (CG) description of low energy QCD_4(N_c) is constructed. The construction is based on the dual transformation of the QCD effective Lagrangian. By considering a large gauge transformation, the charges of this statistical system are identified with magnetic monopoles which carry fractional charges of strength 1/N_c. Furthermore, the creation operator which inserts the magnetic charge in the CG picture is explicitly constructed and demonstrated to have a non-zero vacuum expectation value, indicating that confinement does occur. The Wilson loop operator as well as the creation operator for the domain wall in CG representation is also constructed. Additional support for the D-brane picture suggested by Witten is also found. Lastly, the relation of the CG picture with the instanton-quarks is also discussed.

hep-ph↗

arXiv1997

How strange a non-strange heavy baryon?

We give some general arguments in favor of the large magnitude of matrix elements of an operator associated with nonvalence quarks in heavy hadrons. We estimate a strange matrix element for Λ_b baryon whose valence content is b, u, d quarks. We find a noticeable contribution of the strange quark into the heavy baryon mass on the level 200-300 MeV. The arguments are based on the QCD sum rules and low energy theorems. The physical picture behind of the phenomenon is somewhat similar to the one associated with the large strange content of the nucleon where matrix element. We discuss some possible applications of the obtained result.

hep-ph↗

arXiv1996

Can Asymptotic Series Resolve the Problems of Inflation?

We discuss a cosmological scenario in which inflation is driven by a potential which is motivated by an effective Lagrangian approach to gravity. We exploit the recent arguments \cite{ARZ} that an effective Lagrangian $L_{eff}$ which, by definition, contains operators of arbitrary dimensionality is in general not a convergent but rather an asymptotic series with factorially growing coefficients. This behavior of the effective Lagrangian might be responsible for the resolution of the cosmological constant problem. We argue that the same behavior of the potential gives a natural realization of the inflationary scenario.

hep-ph↗

arXiv1996

Strange and Charmed Quarks in the Nucleon

We discuss the general method of the calculation of the nucleon matrix elements of an operator associated with nonvalence quarks. The method is based on the QCD sum rules and low energy theorems. As an application of these considerations, we calculate the strange quark matrix element as well as the momentum distribution of the strangeness in the nucleon. We also calculate the singlet axial constant associated with $η'$ meson as well as an axial constant associated with heavy quarks.

hep-ph↗

arXiv1996

Lessons from $QCD_2 (N\to\infty)$: Vacuum structure, Asymptotic Series, Instantons and all that

We discuss two dimensional $QCD (N_c\to\infty)$ with fermions in the fundamental as well as adjoint representation. We find factorial growth $\sim (g^2N_cπ)^{2k}\frac{(2k)!(-1)^{k-1}}{(2 π)^{2k}}$ in the coefficients of the large order perturbative expansion. We argue that this behavior is related to classical solutions of the theory, instantons, thus it has nonperturbative origin. Phenomenologically such a growth is related to highly excited states in the spectrum. We also analyze the heavy-light quark system $Q\bar{q}$ within operator product expansion (which it turns out to be an asymptotic series). Some vacuum condensates $\la\bar{q}(x_μD_μ)^{2n}q\ra\sim (x^2)^n\cdot n!$ which are responsible for this factorial growth are also discussed. We formulate some general puzzles which are not specific for 2D physics, but are inevitable features of any asymptotic expansion. We resolve these apparent puzzles within $QCD_2$ and we speculate that analogous puzzles might occur in real 4-dimensional QCD as well.

hep-ph↗

arXiv1996

Two dimensional QCD with matter in adjoint representation: What does it teach us?

We analyse the highly excited states in $QCD_2 (N_{c}\rightarrow\infty) $ with adjoint matter by using such general methods as dispersion relations, duality and unitarity. We find the Hagedorn-like spectrum $ρ(m) \sim m^{-a}\exp(β_H m)$ where parameters $β_H$ and $a$ can be expressed in terms of asymptotics of the following matrix elements $f_{n_{\{k\}}} \sim \la 0|Tr(\barΨΨ)^{k}|n_{k}\ra$. We argue that the asymptotical values $f_{n_{\{k\}}}$ do not depend on $k$ (after appropriate normalization). Thus, we obtain $β_H= (2/π)\sqrt{π/g^2N_{c}}$ and $a = -3/2$ in case of Majorana fermions in the adjoint representation. The Hagedorn temperature is the limiting temperature in this case. We also argue that the chiral condensate $\la 0|Tr(\barΨΨ) |0\ra$ is not zero in the model. Contrary to the 't Hooft model, this condensate does not break down any continuous symmetries and can not be considered as an order parameter. Thus, no Goldstone boson appears as a consequence of the condensation. We also discuss a few apparently different but actually tightly related problems: master field, condensate, wee-partons and constituent quark model in the light cone framework.

hep-ph↗

arXiv1996

Effective Field Theories as Asymptotic Series: From QCD to Cosmology

We present some generic arguments demonstrating that an effective Lagrangian $L_{eff}$ which, by definition, contains operators $O^n$ of arbitrary dimensionality in general is not convergent, but rather an asymptotic series. It means that the behavior of the far distant terms has a specific factorial dependence $L_{eff}\sim \sum_n \frac{c_n O^n}{M^{n}},~c_n\sim n! ,~n\gg1$. We discuss a few apparently different problems, which however have something in common-- the aforementioned $n!-$ behavior: 1.Effective long -distance theory describing the collective fields in QCD; 2.Effective Berry phase potential which is obtained by integrating over the fast degrees of freedom. As is known, the Berry potential is associated with induced local gauge symmetry and might be relevant for the compactification problem at the Planck scale. 3.Nonlocal Lagrangians introduced by Georgi\cite{Georgi} for appropriate treatment of the effective field theories without power expanding. 4.The so-called improved action in lattice field theory where the new, higher dimensional operators have been introduced into the theory in order to reduce the lattice artifacts. 5.Cosmological constant problem and vacuum expectation values in gravity. We discuss some applications of this, seemingly pure academic phenomenon, to various physical problems with typical energies from $1 GeV$ to the Plank scale.

hep-ph↗

arXiv1995

Chiral Condensate, Master Field and all that in $QCD_2 (N\to\infty)$

We discuss the various aspects of two-dimensional $QCD_{2}(N\rightarrow\infty)$ (the 't Hooft model\cite{Hooft}). Our main interest (motivated by the corresponding analysis in the four dimensional QCD) is the vacuum structure of the theory. We use the very general methods in the analysis, such as dispersion relations and duality in order to relate the known spectrum of $QCD_2$ to the different vacuum characteristics. We explicitly calculate (in terms of physical parameters like masses and matrix elements) the chiral condensate as well as the mixed vacuum condensates: $$\la 0|\bar{q}(gε_{μν} G_{μν})^nq |0\ra \sim M_{eff}^{2n}\la 0|\bar{q} q |0\ra .$$ We interpret the factorization property for the mixed vacuum condensates as a reminiscent of the master field at large $N$.

hep-ph↗

arXiv1995

Quark Model, Large Order Behavior and Nonperturbative Wave Functions in QCD

We discuss a few, apparently different (but actually, tightly related) problems: 1. The relation between QCD and valence quark model, 2. The evaluation of the nonlocal condensate $ \la \bar{q}(x)q(0)\ra $, its relation to heavy-light $\bar{q}Q$ quark system and to constituent quark mass, 3. The asymptotic behavior of the nonperturbative pion wave function $ψ(\k, x)$ at $x\rightarrow 0,~1, \k \rightarrow \infty$ and 4. The large order behavior of perturbative series. The analysis is based on such general methods as dispersion relations, duality and PCAC. We use the steepest descent method (also known as semiclassical, or instanton calculus), introduced by Lipatov, in order to calculate the $n-$th moment of the $ψ(\k, x)$ with result $\la\vec{k}_{\perp}^{2n}\ra \sim n!$. This information is converted into the fixing of the asymptotic behavior of $wf$ at large $\k$. This behavior it turns out to be Gaussian commonly used in the phenomenological analyses.The same method determines the asymptotic behavior of the mixed local vacuum condensates $\la\bar{q}G_{μν}^nq\ra\sim n!$ at large $n$ as well as the nonlocal vacuum condensate $ \la \bar{q}(x)q(0)\ra $ which is naturally arises in the description of the heavy-light $\bar{q}Q$ quark system. The relation between nonlocal condensate and constituent quark mass is also discussed.

hep-ph↗