The effects of random magnetic fields are considered in an Ising spin-glass model defined in the limit of infinite-range interactions. The probability distribution for the random magnetic fields is a double Gaussian, which consists of two Gaussian distributions centered respectively, at $+H_{0}$ and $-H_{0}$, presenting the same width $σ$. It is argued that such a distribution is more appropriate for a theoretical description of real systems than its simpler particular two well-known limits, namely the single Gaussian distribution ($σ\gg H_{0}$), and the bimodal one ($σ= 0$). The model is investigated by means of the replica method, and phase diagrams are obtained within the replica-symmetric solution. Critical frontiers exhibiting tricritical points occur for different values of $σ$, with the possibility of two tricritical points along the same critical frontier. To our knowledge, it is the first time that such a behavior is verified for a spin-glass model in the presence of a continuous-distribution random field, which represents a typical situation of a real system. The stability of the replica-symmetric solution is analyzed, and the usual Almeida-Thouless instability is verified for low temperatures. It is verified that, the higher-temperature tricritical point always appears in the region of stability of the replica-symmetric solution; a condition involving the parameters $H_{0}$ and $σ$, for the occurrence of this tricritical point only, is obtained analytically. Some of our results are discussed in view of experimental measurements available in the literature.
We study the decay of the false vacuum in the scaling Ising and tricritical Ising field theories using the Truncated Conformal Space Approach and compare the numerical results to theoretical predictions in the thin wall limit. In the Ising case, the results are consistent with previous studies on the quantum spin chain and the $φ^4$ quantum field theory; in particular we confirm that while the theoretical predictions get the dependence of the bubble nucleation rate on the latent heat right, they are off by a model dependent overall coefficient. The tricritical Ising model allows us on the othe…
我们探讨的相图伊辛自旋的一维链纵横交错的两个垂直的方向,并通过链间耦合。这个系统是一个更简单的,经典的模拟量子哈密顿量已被提出作为一个模型的磁性行为在Nb $_{12}$ O $_{29}$,概念上,作为一个几何形状之间的一个和两个维度。利用平均场论以及Metropolis Monte Carlo和Wang-Landau模拟,我们定量地定位了四个有序相的边界。每一个都成为一个有效的伊辛模型,在大链间耦合时具有唯一的有效耦合。远离这个限制,我们证明了非平凡的临界行为,包括三临界点,分离的第一和第二阶相变。最后,我们提出的证据表明,该模型属于二维伊辛普适类。
Roaming form factors for the tricritical to critical Ising flow
本文研究了由Al. B. Zamolodchikov通过解析延拓的sinh-Gordon S-矩阵,侧重于重整化群流从三临界到临界伊辛模型。我们表明,适当定义的某些sinh-戈登形状因子的漫游限制是相同的形状因子的顺序和无序运营商的无质量流。作为一个副产品,我们还构造了一个半局域场的sinh-Gordon模型,它可以与紫外限制自由无质量玻色子理论中的扭曲场的形状因子。
We study the tricritical Ising universality class using conformal bootstrap techniques. By studying bootstrap constraints originating from multiple correlators on the CFT data of multiple OPEs, we are able to determine the scaling dimension of the spin field $Δ_σ$ in various non-integer dimensions $2 \le d \le 3$. $Δ_σ$ is connected to the critical exponent $η$ that governs the (tri-)critical behaviour of the two point function via the relation, $η= 2 - d + 2 Δ_σ$. Our results for $Δ_σ$ match with the exactly known values in two and three dimensions and are a conjecture for non-integer dimensi…
Dipartimento di Fisica “E. Fermi”, Università di Pisa and INFN, sezione di Pisa(比萨大学费米物理系和意大利国家核物理研究所比萨分部);Université Paris–Saclay, CEA, Institut de Physique Théorique(巴黎-萨克雷大学法国原子能和替代能源委员会理论物理研究所);Theoretical Physics Department, CERN(欧洲核子研究中心理论物理部)
Tricritical Ising (TCI) phase transition is known to occur in several interacting spin and Majorana fermion models and is described in terms of a supersymmetric conformal field theory (CFT) with central charge $c=7/10$. The field content of this CFT is highly nontrivial and includes among its primary fields the Fibonacci anyon, making it of potential interest to strategies seeking to implement fault-tolerant topological quantum computation with non-Abelian phases of matter. In this paper we explore the possibility that a TCI CFT can occur at the edge of a gapped two-dimensional topological sta…
We study the leading and sub-leading magnetic perturbations of the thermal $E_7$ integrable deformation of the tricritical Ising model. In the low-temperature phase, these magnetic perturbations lead to the confinement of the kinks of the model. The resulting meson spectrum can be obtained using the semi-classical quantisation, here extended to include also mesonic excitations composed of two different kinks. An interesting feature of the integrable sub-leading magnetic perturbation of the thermal $E_7$ deformation of the model is the possibility to swap the role of the two operators, i.e. the…
The thermal deformation of the critical point action of the 2D tricritical Ising model gives rise to an exact scattering theory with seven massive excitations based on the exceptional $E_7$ Lie algebra. The high and low temperature phases of this model are related by duality. This duality guarantees that the leading and sub-leading magnetisation operators, $σ(x)$ and $σ'(x)$, in either phase are accompanied by associated disorder operators, $μ(x)$ and $μ'(x)$. Working specifically in the high temperature phase, we write down the sets of bootstrap equations for these four operators. For $σ(x)$ …