More on core instabilities of magnetic monopoles

Striet, J.; Bais, Alexander F.

doi:10.1088/1126-6708/2003/06/022

Cited by 10 publications

(11 citation statements)

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“…The singular point defect itself deforms to a circle: a half-quantum vortex ring (Figs. 1 and 2), called an 'Alice ring' by high energy physicists [8,9,10], which carries a topological charge similar to delocalized magnetic 'Cheshire' charge [11]. This forms an interesting connection between ultra-cold atom experiments and elementary particle physics.…”

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confidence: 99%

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Monopole Core Instability and Alice Rings in Spinor Bose-Einstein Condensates

2003

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We show how the length scale hierarchy, resulting from different interaction strengths in an optically-trapped spin-1 23 Na Bose-Einstein condensate, can lead to intriguing core deformations in singular topological defects. In particular, a point defect can be unstable with respect to the formation of a stable half-quantum vortex ring (an 'Alice ring'), providing a realistic scheme to use dissipation as a sophisticated state engineering tool. We compute the threshold for stability of the point monopole, which is beyond the current experimental regime.PACS numbers: 03.75.Lm,03.75.MnThe rich order parameter space of multi-component Bose-Einstein condensates (BECs) can admit truly 3D topological excitations [1,2,3,4,5], beyond the simple quantized vortices of single-component BECs. Such structures are of interest in a wide range of physical contexts, but dilute atomic BECs offer the unusual advantage that we can fully explore, e.g., the short-range physics in topological defect cores, where the order parameter may explore a larger space than the usual ground state manifold. In this Letter we show how this can result in rich and surprising core structures, by demonstrating a spontaneous deformation of a singular point defect to an energetically stable half-quantum vortex ring.We examine the recently presented case [5] of a defect analogous to the 't Hooft-Polyakov monopole [6], in a antiferromagnetic, or polar, spin-1 BEC [7]. We will show that it is only in the strongly antiferromagnetic regime, which is not attained in current experiments, that its stable core will be the spherically symmetric hedgehog, with a total density depression, of Ref. [5]. In the weakly antiferromagnetic regime that currently holds, the wavelength at which the antiferromagnetic constraint may be violated is much larger than that at which the total density constraint fails. The stable defect core therefore extends to this larger size, and holds non-zero average spin instead of a density zero. The singular point defect itself deforms to a circle: a half-quantum vortex ring (Figs. 1 and 2), called an 'Alice ring' by high energy physicists [8,9,10], which carries a topological charge similar to delocalized magnetic 'Cheshire' charge [11]. This forms an interesting connection between ultra-cold atom experiments and elementary particle physics. It also shows that dissipation, often an obstacle in state engineering, can sometimes perform the intricate final step in producing an exotic object.We consider the BEC of spin-1 atoms. In the absence of a magnetic trapping potential, the macroscopic BEC wave function is determined by a spinor wave function Ψ with three complex components [12,13]. The Hamiltonian density of the classical Gross-Pitaevskii (GP) mean-The stable half-quantum vortex ring (Alice ring), when the energy of an initial spherically symmetric monopole was minimized by continuously deforming the field configuration. The asymptotic distribution of the spin quantization axis d(r) (left), for r ≫ ξa, forms the radial hedgehog. For visu...

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“…To keep Ψ single-valued on the disc bounded by the ring, the macroscopic phase ϕ must change by π around any loop that links the defect circle, while there is also a π-disclination in d on the disc. We identify this structure as a half-quantum vortex line [14,15], forming a closed circular ring, also called an Alice ring [8,9,10,11].…”

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Monopole Core Instability and Alice Rings in Spinor Bose-Einstein Condensates

2003

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“…An Alice string carries a U (1) modulus, corresponding to the internal direction of the flux [60]. When a U (1) modulus is twisted along a closed Alice string (called a vorton), it is nothing but a magnetic monopole [76][77][78]. See Ref.…”

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confidence: 99%

Aharonov-Bohm defects

Chatterjee

Nitta

2020

Phys. Rev. D

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We discuss what happens when a field receiving an Aharonov-Bohm (AB) phase develops a vacuum expectation value (VEV), with an example of an Alice string in a U (1) × SU (2) gauge theory coupled with complex triplet scalar fields. We introduce scalar fields belonging to the doublet representation of SU (2), charged or chargeless under the U (1) gauge symmetry, that receives an AB phase around the Alice string. When the doublet develops a VEV, the Alice string turns to a global string in the absence of the interaction depending on the relative phase between the doublet and triplet, while, in the presence of such an interaction, the Alice string is confined by a soliton or domain wall and therefore the spontaneous breaking of a spatial rotation around the string is accompanied. We call such an object induced by an AB phase as an "AB defect", and argue that such a phenomenon is ubiquitously appearing in various systems.

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“…A monopole in the conventional Alice theory (SO(3) gauge theory with scalar fields of the fiveplet) admitting Alice strings was studied in Refs. [61][62][63][64]. In particular, a monopole is not spherical and decays into a twisted Alice ring depending on choice of parameters [62,63].…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Note on a solution to domain wall problem with the Lazarides-Shafi mechanism in axion dark matter models

Chatterjee

Higaki²,

Nitta³

2020

Phys. Rev. D

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Axion is a promising candidate of dark matter. After the Peccei-Quinn symmetry breaking, axion strings are formed and attached by domain walls when the temperature of the universe becomes comparable to the QCD scale. Such objects can cause cosmological disasters if they are long-lived. As a solution for it, the Lazarides-Shafi mechanism is often discussed through introduction of a new non-Abelian (gauge) symmetry. We study this mechanism in detail and show configuration of strings and walls. Even if Abelian axion strings with a domain wall number greater than one are formed in the early universe, each of them is split into multiple Alice axion strings due to a repulsive force between the Alice strings even without domain wall. When domain walls are formed as the universe cools down, a single Alice string can be attached by a single wall because a vacuum is connected by a non-Abelian rotation without changing energy. Even if an Abelian axion string attached by domain walls are created due to the Kibble Zurek mechanism at the chiral phase transition, such strings are also similarly split into multiple Alice strings attached by walls in the presence of the domain wall tension. Such walls do not form stable networks since they collapse by the tension of the walls, emitting axions.

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More on core instabilities of magnetic monopoles

Cited by 10 publications

References 11 publications

Monopole Core Instability and Alice Rings in Spinor Bose-Einstein Condensates

Monopole Core Instability and Alice Rings in Spinor Bose-Einstein Condensates

Aharonov-Bohm defects

Note on a solution to domain wall problem with the Lazarides-Shafi mechanism in axion dark matter models

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