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Braid Group Representations, Modular Data, and the Classification of Majorana Zero Mode Fusion Rules in 2D Topological Superconductors

Rowan Brad Quni-Gudzinas

Published Sep 7, 2026• 0 citations
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Abstract

We investigate whether the braid group representation on $N$ anyons uniquely determines the modular data ($S$ and $T$ matrices) of a non-Abelian topological order, and whether this framework classifies all fusion rules for Majorana zero modes (MZMs) in 2D topological superconductors. We show that the local $N$-anyon braid group representation constrains the modular data up to finite gauge ambiguity but does not uniquely fix the global $S$-matrix without specifying the underlying spin structure. For MZMs, the braid generators satisfy the Ising anyon $R$-matrix with the asymptotic Hecke relation $\sigma_i^2 = 1$ (up to phase), which rigidly fixes the local $F$ and $R$ symbols of the Ising category. Consequently, the fusion rules are strictly of Ising type ($\sigma \times \sigma = 1 + \psi$), precluding alternative non-Abelian fusion rules. The $T$-matrix is determined by topological spins, but the full $S$-matrix depends on the spin structure of the underlying manifold, reflecting the super-modular structure of the theory. ## 1. Introduction Topological quantum computation exploits the non-Abelian statistics of anyons—quasiparticle excitations in two-dimensional systems whose braiding operations are represented by non-commuting unitary matrices on a degenerate ground-state manifold [1]. A central question is whether the local braiding data of $N$ anyons suffices to reconstruct the full modular data of the underlying topological order (TO), or whether additional global information is required. This question has direct physical consequences for 2D topological superconductors (TSCs) hosting Majorana zero modes (MZMs), where the anyonic excitations are vortices binding MZMs and the fermionic quasiparticle is a transparent (local) fermion [2,3]. The modular data of a TO consists of the $S$-matrix, which encodes the mutual braiding statistics of anyons, and the $T$-matrix, which encodes the topological spins. Together, these matrices form a projective representation of t

DOI
10.5281/zenodo.22641304

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Braid Group Representations, Modular Data, and the Classification of Majorana Zero Mode Fusion Rules in 2D Topological Superconductors

Rowan Brad Quni-Gudzinas

Majorana zero modes (MZMs) localized on vortices of a two-dimensional topological superconductor carry a projective representation of the braid group, and the associated anyon theory is encoded in a modular tensor category whose fusion rules and modular data ($S$ and $T$ matrices) determine the topological order. We address two questions: whether the braid group representation on $N$ anyons uniquely determines the modular data of the underlying non-Abelian topological order, and whether a representation-theoretic framework can classify all possible fusion rules for MZMs in 2D topological superconductors. We develop a classification pipeline that (i) fixes the local MZM algebra as the Clifford algebra generated by $2n$ Majorana operators, (ii) imposes the pentagon and hexagon coherence equations on candidate braided fusion structures, and (iii) filters candidates by modular-data consistency conditions, including the Verlinde formula and Frobenius–Schur indicators. As a fully worked example we compute, with explicit arithmetic, the modular $S$ matrix and total quantum dimension for the Ising-type theory relevant to chiral $p$-wave superconductors, obtaining $\mathcal{D} = 2$ and verifying unitarity of $S$ to machine precision. We then analyze metaplectic categories $SO(N)_2$, which generalize the Ising/MZM fusion pattern, and show how Property F (finiteness of braid images) constrains the classification. We argue that the framework classifies MZM fusion rules up to gauging and extension operations, but that non-semisimple and non-unitary candidates escape the semisimple machinery; we state falsification criteria and open problems. ## 1. Introduction A two-dimensional topological superconductor (2D TSC) supports vortices that bind Majorana zero modes (MZMs): self-adjoint fermionic operators $\gamma_i = \gamma_i^\dagger$ obeying the Clifford algebra $\{\gamma_i,\gamma_j\} = 2\delta_{ij}$. Exchanging vortices $i$ and $j$ acts on the ground-state manifold by the operato Full text and updates: papers.qnfo.org/papers/braid-group-representations-modular-data-and-the-classification-of-majo-5099abb8/

•Oct 1, 2026•0 citations

Majorana Zero-Mode Parity, the Hexagon Equation, and Chiral Edge Modes in 2D Topological Superconductors

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In a two-dimensional topological superconductor hosting vortices with Majorana zero modes (MZMs), the exchange of vortices yields a projective representation of the braid group. We investigate whether the full anyonic exchange matrix is uniquely determined by the MZM parity operators and whether consistency with the hexagon equation of the Ising modular tensor category necessitates chiral edge modes. We show that the MZM algebra $\gamma_i\gamma_j + \gamma_j\gamma_i = 2\delta_{ij}$ fixes the non-Abelian structure of the exchange operator up to an overall Abelian phase. Completing the modular data and imposing the Ising hexagon equation requires a topological spin $\theta_\sigma = e^{i\pi/8}$ for the vortices, which via the Gauss-Milgram sum implies a chiral central charge $c = 1/2 \pmod{8}$. Non-chiral systems with $c=0$ yield incompatible topological spins, demonstrating that the MZM parity operators alone do not uniquely fix the full anyonic exchange matrix. We discuss implications for extrinsic defects and anomaly inflow. ## 1. Introduction Non-Abelian anyons in two-dimensional topological phases offer a route to topologically protected quantum computation. In a class of topological superconductors—exemplified by the chiral $p_x + ip_y$ state—vortices trap Majorana zero modes (MZMs) whose algebraic exchange realizes a projective representation of the braid group (Ivanov, 2001). The resulting anyon theory is the Ising theory, with anyon types $\{1, \sigma, \psi\}$, where $\sigma$ labels the vortex and $\psi$ labels the fermion. A central question is whether the MZM parity operators—the only local algebraic data available from the zero-mode subspace—uniquely determine the full anyonic exchange matrix, including all phases. Moreover, the consistency of braiding with the hexagon equation, a defining axiom of modular tensor categories (MTCs), imposes constraints relating the topological spin to the chiral central charge. This raises the question of whether non-chira

•Sep 7, 2026•0 citations

Braid Group Representations and Modular Data: Non-Uniqueness, Finite Images, and the Ising Test Case

Rowan Brad Quni-Gudzinas

A central question in the theory of topological order asks whether the braid group representation $B_N$ carried by $N$ non-Abelian anyons uniquely determines the modular data — the $S$ and $T$ matrices — of the underlying topological quantum field theory. We reconcile three lines of analysis into a single assessment. Structurally, we formalize the question as a reduction map $\Phi$ from modular tensor category data to projective braid group representations, whose kernel is the locus of potential counterexamples. Two rigorous finiteness results constrain the problem: braid representations from twisted quantum doubles of finite groups factor through finite groups, and the $SO(N)_2$/$O(N)_2$ braid representations are Gaussian with finite image. We then perform an explicit computation on the Ising anyon model — the canonical non-Abelian order of Majorana zero modes — reconstructing the topological spins $\theta_\sigma = e^{i\pi/8}$, $\theta_\psi = -1$, the total quantum dimension $\mathcal{D}=2$, and the full $S$ matrix from the braid eigenvalues, with all arithmetic shown. We exhibit a Galois-conjugate deformation $\mathrm{Ising}(7)$ with identical fusion rules but distinct $S$ matrix, and verify that its braid representation is inequivalent to the Ising representation on $B_3$ by an explicit trace computation, while remaining indistinguishable at the level of fusion rules. We conclude that braid representations constrain but do not provably uniquely determine modular data in general: uniqueness can hold only under additional hypotheses, and the Majorana fusion-rule classification is not closed by braid data alone. The affirmative claim that braiding is a complete invariant is restricted to a narrower regime than sometimes asserted, and we document this divergence explicitly. ## 1. Introduction Non-Abelian anyons in two spatial dimensions are characterized by two layers of algebraic structure. The first is combinatorial: fusion rules $N_{ab}^c$ specifying how anyon c Full text and updates: papers.qnfo.org/papers/braid-group-representations-and-modular-data-non-uniqueness-finite-images-and-th/

•Oct 1, 2026•0 citations

Majorana Zero Modes, Super-Modular Categories, and the Indistinguishability of $\pi/2$ Berry Phase in Vortex Exchange

Rowan Brad Quni-Gudzinas

The exchange statistics of Majorana zero modes (MZMs) in a two-dimensional topological superconductor are commonly modeled using the Ising anyon theory. However, the intrinsic topological order of a fermionic system is described by a super-modular tensor category (SMC), specifically sIsing, which contains a transparent fermion. We rigorously demonstrate that the modular data of the underlying SMC is insufficient to uniquely determine the braiding statistics of vortices binding MZMs. Fixing the exchange statistics requires specifying a minimal modular extension (MME) of the SMC. When the Ising unitary modular tensor category (UMTC) is chosen as the MME, the vortex exchange statistics exactly match those of Ising anyons, yielding a non-Abelian Berry phase difference of $\pi/2$ between fusion channels. Consequently, this $\pi/2$ phase is not distinguishable from standard Ising anyon braiding in interferometric measurements; rather, it is identical to it. We conclude that distinguishing fermionic topological orders requires probing the specific MME via observables beyond standard anyon interferometry. ## 1. Introduction Majorana zero modes (MZMs) localized at vortices in two-dimensional (2D) topological superconductors are prime candidates for topological quantum computation. The non-Abelian exchange statistics of these vortices are widely described using the Ising anyon theory. However, a 2D topological superconductor is an intrinsically fermionic system, meaning its topological order is not strictly captured by a standard unitary modular tensor category (UMTC). Instead, it is described by a super-modular tensor category (SMC). This raises a fundamental question: can the exchange statistics of MZMs be uniquely derived from the modular data of the underlying SMC? Furthermore, does this derivation predict a non-Abelian Berry phase of $\pi/2$ for vortex exchange that is distinguishable from standard Ising anyon braiding in interferometry? In this preprint, we address t

•Sep 7, 2026•0 citations

Distinguishing SO(3)2 and Ising Topological Orders via Four-Point Interferometry

Rowan Brad Quni-Gudzinas

Majorana zero modes (MZMs) are canonically described by the Ising topological quantum field theory (TQFT), equivalent to SU(2)2 Chern-Simons theory. We investigate whether the braid-group representation governing MZMs could instead arise as the non-Abelian sector of an SO(3)2 Chern-Simons theory (equivalent to SU(2)4), and whether four-point interferometry can experimentally distinguish these topological orders. The non-Abelian sector of SO(3)2 yields a braid-group representation locally indistinguishable from Ising anyons for two-quasiparticle braiding, but differs fundamentally in its fusion rules. Specifically, the SO(3)2 non-Abelian anyon $v$ (spin-1) obeys $v \times v = 1 + v + \psi$, whereas the Ising $\sigma$ anyon obeys $\sigma \times \sigma = 1 + \psi$. We compute the four-point braiding matrices and evaluate the interferometric visibility for a Fabry-Pérot interferometer enclosing four anyons. The presence of the $v \times v \to v$ fusion channel introduces an additional interference path with a distinct conformal weight, providing a falsifiable signature distinguishing SO(3)2 from Ising. ## 1. Introduction Majorana zero modes (MZMs) are localized zero-energy excitations in topological superconductors that exhibit non-Abelian statistics. Canonically, MZMs are described by the Ising topological quantum field theory (TQFT), a framework describing topological phases of matter, which corresponds to the SU(2)2 Chern-Simons gauge theory. Chern-Simons theory is a topological gauge theory in 2+1 dimensions whose quantization yields anyonic quasiparticles. We investigate whether the braid-group representation governing MZMs could instead arise as the non-Abelian sector of an SO(3)2 Chern-Simons theory. We demonstrate that while two-quasiparticle braiding is locally indistinguishable from Ising anyons, the theories differ fundamentally in their fusion rules. We propose that four-point interferometry can experimentally distinguish these two topological orders by det

•Sep 7, 2026•0 citations

Dynamical Modification of Ising Anyon Braiding Statistics in Finite-Size Majorana Vortex Lattices

Rowan Brad Quni-Gudzinas

Majorana zero modes (MZMs) localized in superconducting vortices are predicted to realize Ising anyon non-Abelian statistics. In finite-size vortex lattices, overlapping MZM wavefunctions generate exponentially decaying energy splittings. We investigate whether these finite-size effects merely perturb the ideal Ising braid group representation or fundamentally alter it into a distinct, dynamically dependent representation. By modeling a two-dimensional topological superconductor with an effective low-energy Hamiltonian incorporating exponentially decaying overlap terms, we numerically evaluate the time-evolution operator during adiabatic braiding. Our analysis shows that finite-size effects introduce a non-commuting dynamical phase that modifies the ideal Ising braid matrix. This results in a time-dependent braid matrix that alters expected interferometric conductance oscillations. Specifically, the conductance oscillations exhibit a phase shift proportional to the braiding time and inter-vortex distance, scaling as $\delta \phi \propto \tau \Delta e^{-R/\xi}$ [to verify]. The non-Abelian nature appears degraded, with the braid matrix depending on the adiabatic trajectory and duration rather than solely on its topological class. This suggests interferometry can dynamically detect these finite-size modifications. ## 1. Introduction Majorana zero modes (MZMs) in topological superconductors are predicted to exhibit non-Abelian braiding statistics, forming the basis for topological quantum computation. In a $p+ip$ superconductor or similar platforms, vortices trap MZMs whose braiding is described by the Ising anyon model. However, realistic systems are finite, and MZMs localized at neighboring vortices have overlapping wavefunctions, leading to exponentially small energy splittings. While often treated as a negligible perturbation, the impact of these splittings on the braid group representation during finite-time braiding remains an open question. Here, we analyze the

•Sep 8, 2026•0 citations
We investigate whether the braid group representation on NNN anyons uniquely determines the modular data (SSS and TTT matrices) of a non-Abelian topological order, and whether this framework classifies all fusion rules for Majorana zero modes (MZMs) in 2D topological superconductors. We show that the local NNN-anyon braid group representation constrains the modular data up to finite gauge ambiguity but does not uniquely fix the global SSS-matrix without specifying the underlying spin structure. For MZMs, the braid generators satisfy the Ising anyon RRR-matrix with the asymptotic Hecke relation σi2=1\sigma_i^2 = 1σi2​=1 (up to phase), which rigidly fixes the local FFF and RRR symbols of the Ising category. Consequently, the fusion rules are strictly of Ising type (σ×σ=1+ψ\sigma \times \sigma = 1 + \psiσ×σ=1+ψ), precluding alternative non-Abelian fusion rules. The TTT-matrix is determined by topological spins, but the full SSS-matrix depends on the spin structure of the underlying manifold, reflecting the super-modular structure of the theory. ## 1. Introduction Topological quantum computation exploits the non-Abelian statistics of anyons—quasiparticle excitations in two-dimensional systems whose braiding operations are represented by non-commuting unitary matrices on a degenerate ground-state manifold [1]. A central question is whether the local braiding data of NNN anyons suffices to reconstruct the full modular data of the underlying topological order (TO), or whether additional global information is required. This question has direct physical consequences for 2D topological superconductors (TSCs) hosting Majorana zero modes (MZMs), where the anyonic excitations are vortices binding MZMs and the fermionic quasiparticle is a transparent (local) fermion [2,3]. The modular data of a TO consists of the SSS-matrix, which encodes the mutual braiding statistics of anyons, and the TTT-matrix, which encodes the topological spins. Together, these matrices form a projective representation of t
Majorana zero modes (MZMs) localized on vortices of a two-dimensional topological superconductor carry a projective representation of the braid group, and the associated anyon theory is encoded in a modular tensor category whose fusion rules and modular data (SSS and TTT matrices) determine the topological order. We address two questions: whether the braid group representation on NNN anyons uniquely determines the modular data of the underlying non-Abelian topological order, and whether a representation-theoretic framework can classify all possible fusion rules for MZMs in 2D topological superconductors. We develop a classification pipeline that (i) fixes the local MZM algebra as the Clifford algebra generated by 2n2n2n Majorana operators, (ii) imposes the pentagon and hexagon coherence equations on candidate braided fusion structures, and (iii) filters candidates by modular-data consistency conditions, including the Verlinde formula and Frobenius–Schur indicators. As a fully worked example we compute, with explicit arithmetic, the modular SSS matrix and total quantum dimension for the Ising-type theory relevant to chiral ppp-wave superconductors, obtaining D=2\mathcal{D} = 2D=2 and verifying unitarity of SSS to machine precision. We then analyze metaplectic categories SO(N)2SO(N)_2SO(N)2​, which generalize the Ising/MZM fusion pattern, and show how Property F (finiteness of braid images) constrains the classification. We argue that the framework classifies MZM fusion rules up to gauging and extension operations, but that non-semisimple and non-unitary candidates escape the semisimple machinery; we state falsification criteria and open problems. ## 1. Introduction A two-dimensional topological superconductor (2D TSC) supports vortices that bind Majorana zero modes (MZMs): self-adjoint fermionic operators γi=γi†\gamma_i = \gamma_i^\daggerγi​=γi†​ obeying the Clifford algebra {γi,γj}=2δij\{\gamma_i,\gamma_j\} = 2\delta_{ij}{γi​,γj​}=2δij​. Exchanging vortices iii and jjj acts on the ground-state manifold by the operato Full text and updates: papers.qnfo.org/papers/braid-group-representations-modular-data-and-the-classification-of-majo-5099abb8/
In a two-dimensional topological superconductor hosting vortices with Majorana zero modes (MZMs), the exchange of vortices yields a projective representation of the braid group. We investigate whether the full anyonic exchange matrix is uniquely determined by the MZM parity operators and whether consistency with the hexagon equation of the Ising modular tensor category necessitates chiral edge modes. We show that the MZM algebra γiγj+γjγi=2δij\gamma_i\gamma_j + \gamma_j\gamma_i = 2\delta_{ij}γi​γj​+γj​γi​=2δij​ fixes the non-Abelian structure of the exchange operator up to an overall Abelian phase. Completing the modular data and imposing the Ising hexagon equation requires a topological spin θσ=eiπ/8\theta_\sigma = e^{i\pi/8}θσ​=eiπ/8 for the vortices, which via the Gauss-Milgram sum implies a chiral central charge c=1/2(mod8)c = 1/2 \pmod{8}c=1/2(mod8). Non-chiral systems with c=0c=0c=0 yield incompatible topological spins, demonstrating that the MZM parity operators alone do not uniquely fix the full anyonic exchange matrix. We discuss implications for extrinsic defects and anomaly inflow. ## 1. Introduction Non-Abelian anyons in two-dimensional topological phases offer a route to topologically protected quantum computation. In a class of topological superconductors—exemplified by the chiral px+ipyp_x + ip_ypx​+ipy​ state—vortices trap Majorana zero modes (MZMs) whose algebraic exchange realizes a projective representation of the braid group (Ivanov, 2001). The resulting anyon theory is the Ising theory, with anyon types {1,σ,ψ}\{1, \sigma, \psi\}{1,σ,ψ}, where σ\sigmaσ labels the vortex and ψ\psiψ labels the fermion. A central question is whether the MZM parity operators—the only local algebraic data available from the zero-mode subspace—uniquely determine the full anyonic exchange matrix, including all phases. Moreover, the consistency of braiding with the hexagon equation, a defining axiom of modular tensor categories (MTCs), imposes constraints relating the topological spin to the chiral central charge. This raises the question of whether non-chira
A central question in the theory of topological order asks whether the braid group representation BNB_NBN​ carried by NNN non-Abelian anyons uniquely determines the modular data — the SSS and TTT matrices — of the underlying topological quantum field theory. We reconcile three lines of analysis into a single assessment. Structurally, we formalize the question as a reduction map Φ\PhiΦ from modular tensor category data to projective braid group representations, whose kernel is the locus of potential counterexamples. Two rigorous finiteness results constrain the problem: braid representations from twisted quantum doubles of finite groups factor through finite groups, and the SO(N)2SO(N)_2SO(N)2​/O(N)2O(N)_2O(N)2​ braid representations are Gaussian with finite image. We then perform an explicit computation on the Ising anyon model — the canonical non-Abelian order of Majorana zero modes — reconstructing the topological spins θσ=eiπ/8\theta_\sigma = e^{i\pi/8}θσ​=eiπ/8, θψ=−1\theta_\psi = -1θψ​=−1, the total quantum dimension D=2\mathcal{D}=2D=2, and the full SSS matrix from the braid eigenvalues, with all arithmetic shown. We exhibit a Galois-conjugate deformation Ising(7)\mathrm{Ising}(7)Ising(7) with identical fusion rules but distinct SSS matrix, and verify that its braid representation is inequivalent to the Ising representation on B3B_3B3​ by an explicit trace computation, while remaining indistinguishable at the level of fusion rules. We conclude that braid representations constrain but do not provably uniquely determine modular data in general: uniqueness can hold only under additional hypotheses, and the Majorana fusion-rule classification is not closed by braid data alone. The affirmative claim that braiding is a complete invariant is restricted to a narrower regime than sometimes asserted, and we document this divergence explicitly. ## 1. Introduction Non-Abelian anyons in two spatial dimensions are characterized by two layers of algebraic structure. The first is combinatorial: fusion rules NabcN_{ab}^cNabc​ specifying how anyon c Full text and updates: papers.qnfo.org/papers/braid-group-representations-and-modular-data-non-uniqueness-finite-images-and-th/
Majorana Zero Modes, Super-Modular Categories, and the Indistinguishability of π/2\pi/2π/2 Berry Phase in Vortex Exchange
The exchange statistics of Majorana zero modes (MZMs) in a two-dimensional topological superconductor are commonly modeled using the Ising anyon theory. However, the intrinsic topological order of a fermionic system is described by a super-modular tensor category (SMC), specifically sIsing, which contains a transparent fermion. We rigorously demonstrate that the modular data of the underlying SMC is insufficient to uniquely determine the braiding statistics of vortices binding MZMs. Fixing the exchange statistics requires specifying a minimal modular extension (MME) of the SMC. When the Ising unitary modular tensor category (UMTC) is chosen as the MME, the vortex exchange statistics exactly match those of Ising anyons, yielding a non-Abelian Berry phase difference of π/2\pi/2π/2 between fusion channels. Consequently, this π/2\pi/2π/2 phase is not distinguishable from standard Ising anyon braiding in interferometric measurements; rather, it is identical to it. We conclude that distinguishing fermionic topological orders requires probing the specific MME via observables beyond standard anyon interferometry. ## 1. Introduction Majorana zero modes (MZMs) localized at vortices in two-dimensional (2D) topological superconductors are prime candidates for topological quantum computation. The non-Abelian exchange statistics of these vortices are widely described using the Ising anyon theory. However, a 2D topological superconductor is an intrinsically fermionic system, meaning its topological order is not strictly captured by a standard unitary modular tensor category (UMTC). Instead, it is described by a super-modular tensor category (SMC). This raises a fundamental question: can the exchange statistics of MZMs be uniquely derived from the modular data of the underlying SMC? Furthermore, does this derivation predict a non-Abelian Berry phase of π/2\pi/2π/2 for vortex exchange that is distinguishable from standard Ising anyon braiding in interferometry? In this preprint, we address t
Majorana zero modes (MZMs) are canonically described by the Ising topological quantum field theory (TQFT), equivalent to SU(2)2 Chern-Simons theory. We investigate whether the braid-group representation governing MZMs could instead arise as the non-Abelian sector of an SO(3)2 Chern-Simons theory (equivalent to SU(2)4), and whether four-point interferometry can experimentally distinguish these topological orders. The non-Abelian sector of SO(3)2 yields a braid-group representation locally indistinguishable from Ising anyons for two-quasiparticle braiding, but differs fundamentally in its fusion rules. Specifically, the SO(3)2 non-Abelian anyon vvv (spin-1) obeys v×v=1+v+ψv \times v = 1 + v + \psiv×v=1+v+ψ, whereas the Ising σ\sigmaσ anyon obeys σ×σ=1+ψ\sigma \times \sigma = 1 + \psiσ×σ=1+ψ. We compute the four-point braiding matrices and evaluate the interferometric visibility for a Fabry-Pérot interferometer enclosing four anyons. The presence of the v×v→vv \times v \to vv×v→v fusion channel introduces an additional interference path with a distinct conformal weight, providing a falsifiable signature distinguishing SO(3)2 from Ising. ## 1. Introduction Majorana zero modes (MZMs) are localized zero-energy excitations in topological superconductors that exhibit non-Abelian statistics. Canonically, MZMs are described by the Ising topological quantum field theory (TQFT), a framework describing topological phases of matter, which corresponds to the SU(2)2 Chern-Simons gauge theory. Chern-Simons theory is a topological gauge theory in 2+1 dimensions whose quantization yields anyonic quasiparticles. We investigate whether the braid-group representation governing MZMs could instead arise as the non-Abelian sector of an SO(3)2 Chern-Simons theory. We demonstrate that while two-quasiparticle braiding is locally indistinguishable from Ising anyons, the theories differ fundamentally in their fusion rules. We propose that four-point interferometry can experimentally distinguish these two topological orders by det
Majorana zero modes (MZMs) localized in superconducting vortices are predicted to realize Ising anyon non-Abelian statistics. In finite-size vortex lattices, overlapping MZM wavefunctions generate exponentially decaying energy splittings. We investigate whether these finite-size effects merely perturb the ideal Ising braid group representation or fundamentally alter it into a distinct, dynamically dependent representation. By modeling a two-dimensional topological superconductor with an effective low-energy Hamiltonian incorporating exponentially decaying overlap terms, we numerically evaluate the time-evolution operator during adiabatic braiding. Our analysis shows that finite-size effects introduce a non-commuting dynamical phase that modifies the ideal Ising braid matrix. This results in a time-dependent braid matrix that alters expected interferometric conductance oscillations. Specifically, the conductance oscillations exhibit a phase shift proportional to the braiding time and inter-vortex distance, scaling as δϕ∝τΔe−R/ξ\delta \phi \propto \tau \Delta e^{-R/\xi}δϕ∝τΔe−R/ξ [to verify]. The non-Abelian nature appears degraded, with the braid matrix depending on the adiabatic trajectory and duration rather than solely on its topological class. This suggests interferometry can dynamically detect these finite-size modifications. ## 1. Introduction Majorana zero modes (MZMs) in topological superconductors are predicted to exhibit non-Abelian braiding statistics, forming the basis for topological quantum computation. In a p+ipp+ipp+ip superconductor or similar platforms, vortices trap MZMs whose braiding is described by the Ising anyon model. However, realistic systems are finite, and MZMs localized at neighboring vortices have overlapping wavefunctions, leading to exponentially small energy splittings. While often treated as a negligible perturbation, the impact of these splittings on the braid group representation during finite-time braiding remains an open question. Here, we analyze the