Vladimir Rosenhaus
These notes are a short introduction to the Sachdev-Ye-Kitaev model. We discuss: SYK and tensor models as a new class of large N quantum field theories, the near-conformal invariance in the infrared, the computation of correlation functions, generalizations of SYK, and applications to AdS/CFT and strange metals.
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The Sachdev-Ye-Kitaev (SYK) model attracts attention in the context of information scrambling, which represents delocalization of quantum information and is quantified by the out-of-time-ordered correlators (OTOC). The SYK model contains $N$ fermions with disordered and four-body interactions. Here, we introduce a variant of the SYK model, which we refer to as the Wishart SYK model. We investigate the Wishart SYK model for complex fermions and that for hard-core bosons. We show that the ground state of the Wishart SYK model is massively degenerate and the residual entropy is extensive, and tha…
We study the effect of non-Gaussian average over the random couplings in a complex version of the celebrated Sachdev-Ye-Kitaev (SYK) model. Using a Polchinski-like equation and random tensor Gaussian universality, we show that the effect of this non-Gaussian averaging leads to a modification of the variance of the Gaussian distribution of couplings at leading order in N. We then derive the form of the effective action to all orders. An explicit computation of the modification of the variance in the case of a quartic perturbation is performed for both the complex SYK model mentioned above and t…
We show that a non-Hermitian two coupled Sachdev-Ye-Kitaev (SYK) model can provide thermodynamic structure equivalent to Hermitian two coupled SYK model. The energy spectrum, the entanglement degree of the ground states and the low energy effective action of this model are not influenced by the non-Hermiticity. The novel biorthogonal ground states demonstrates that two SYK sites, one of which can be in the ground state and the other in the Schwarzian excited state by tuning the non-Hermiticity. We find evidence that the free energy is independent of the non-Hermiticity.
Stabilizer Entropy and entanglement complexity in the Sachdev-Ye-Kitaev model
研究Sachdev-Ye-Kitaev模型中退相干熵与纠缠复杂性的相互作用，揭示SYK4的复杂性与SYK2的非普遍性。
We consider the Sachdev-Ye-Kitaev (SYK) model where interaction involves $q$ fermions at a time. We find the next order correction to the thermal two-point function in the large $q$ expansion. Using this result we find the next order correction to the SYK free energy.
We study $\mathcal{N}=2$ supersymmetric Sachdev-Ye-Kitaev (SYK) models with complex fermions at non-zero background charge. Motivated by multi-charge supersymmetric black holes, we propose a new $\mathcal{N}=2$ SYK model with multiple $U(1)$ symmetries, integer charges, and a non-vanishing supersymmetric index, realizing features not present in known SYK models. In both models, a conformal solution with a super-Schwarzian mode emerges at low temperatures, signalling the appearance of nearly AdS$_2$/BPS physics. However, in contrast to complex SYK, the fermion scaling dimension depends on the b…
The Sachdev-Ye-Kitaev (SYK) model is an all-to-all interacting Majorana fermion model for many-body quantum chaos and the holographic correspondence. Here we construct fermionic all-to-all Floquet quantum circuits of random four-body gates designed to capture key features of SYK dynamics. Our circuits can be built using local ingredients in Majorana devices, namely charging-mediated interactions and braiding Majorana zero modes. This offers an analog-digital route to SYK quantum simulations that reconciles all-to-all interactions with the topological protection of Majorana zero modes, a key fe…
Deviations from maximal entanglement for eigenstates of the Sachdev-Ye-Kitaev model
针对SYK模型的谱中间本征态，研究证明尺寸占系统恒定比例的子系统的纠缠熵与最大熵的偏差至少为一个正常数，明确了其与随机态纠缠熵的差异。
We continue the investigation of coupled Sachdev-Ye-Kitaev(SYK) models without Schwarzian action dominance. Like the original SYK, at large N and low energies these models have an approximate reparametrization symmetry. However, the dominant action for reparametrizations is non-local due to the presence of irrelevant local operator with small conformal dimension. We semi-analytically study different thermodynamic properties and the 4-point function and demonstrate that they significantly differ from the Schwarzian prediction. However, the residual entropy and maximal chaos exponent are the sam…
Spread of entanglement in a Sachdev-Ye-Kitaev chain
我们研究了在热场双态（TFD）中制备的Majorana费米子的Sachdev-Ye-Kitaev（SYK）链的两半之间的Rényi熵的传播。SYK链模型是一个混沌多体系统模型，它描述了一个一维晶格的马约拉纳费米子，空间局域随机四次相互作用。我们发现，对于整数Rényi指数$n>1$，Rényi纠缠熵在一个参数上小于预期的值处饱和.这意味着SYK链的TFD状态不会迅速热化，尽管是最大的混乱：相反，它迅速接近预热状态。我们比较我们的结果的热化的签名中观察到的其他淬火的SYK模型，并从近$\mathrm{AdS}_2$重力的直觉。
The Sachdev-Ye-Kitaev (SYK) model describes interacting fermionic zero modes in zero spatial dimensions, e.g. quantum dot, with interactions strong enough to completely washout quasiparticle excitations in the infrared. In this paper, we consider the complex-valued SYK model at initial temperature $T$ and chemical potential $μ$ coupled to a large reservoir by a quench at time $t=0$. The reservoir is kept at zero temperature and charge neutrality. We find that the dynamics of the discharging process of the SYK quantum dot reveals a distinctive characteristic of the SYK non-Fermi liquid (nFl) st…
We study the Lindbladian dynamics of the Sachdev-Ye-Kitaev (SYK) model, where the SYK model is coupled to Markovian reservoirs with jump operators that are either linear or quadratic in the Majorana fermion operators. Here, the linear jump operators are non-random while the quadratic jump operators are sampled from a Gaussian distribution. In the limit of large $N$, where $N$ is the number of Majorana fermion operators, and also in the limit of large $N$ and $M$, where $M$ is the number of jump operators, the SYK Lindbladians are analytically tractable, and we obtain their stationary Green's f…
The Spectrum in the Sachdev-Ye-Kitaev Model
SYK模型由$0+1$维的$N\gg 1$费米子组成，具有随机的全对全四次相互作用。最近，Kitaev发现SYK模型是最大混沌的，并提出将其作为全息模型。我们求解了Schwinger-Dyson方程，计算了SYK中两粒子态的谱，发现了一个连续和离散的塔。四点函数表示为频谱上的和。对离散塔上的和进行评估。
Given a class of $q$-local Hamiltonians, is it possible to find a simple variational state whose energy is a finite fraction of the ground state energy in the thermodynamic limit? Whereas product states often provide an affirmative answer in the case of bosonic (or qubit) models, we show that Gaussian states fail dramatically in the fermionic case, like for the Sachdev-Ye-Kitaev (SYK) models. This prompts us to propose a new class of wavefunctions for SYK models inspired by the variational coupled cluster algorithm. We introduce a static ("0+0D") large-$N$ field theory to study the energy, two…
The Sachdev-Ye-Kitaev (SYK) model is a quantum mechanical model of fermions interacting with $q$-body random couplings. For $q=2$, it describes free particles, and is non-chaotic in the many-body sense, while for $q>2$ it is strongly interacting and exhibits many-body chaos. In this work we study the entanglement entropy (EE) of the SYK$q$ models, for a bipartition of $N$ real or complex fermions into subsystems containing $2m$ real/$m$ complex fermions and $N-2m$/$N-m$ fermions in the remainder. For the free model SYK$2$, we obtain an analytic expression for the EE, derived from the $β$-Jacob…
We study the entanglement entropy of eigenstates (including the ground state) of the Sachdev-Ye-Kitaev model. We argue for a volume law, whose coefficient can be calculated analytically from the density of states. The coefficient depends on not only the energy density of the eigenstate but also the subsystem size. Very recent numerical results of Liu, Chen, and Balents confirm our analytical results.
Entanglement is one of the most important concepts in quantum physics. We review recent progress in understanding the quantum entanglement in many-body systems using large-$N$ solvable models: the Sachdev-Ye-Kitaev (SYK) model and its generalizations. We present the study of entanglement entropy in the original SYK Model using three different approaches: the exact diagonalization, the eigenstate thermalization hypothesis, and the path-integral representation. For coupled SYK models, the entanglement entropy shows linear growth and saturation at the thermal value. The saturation is related to r…
Sachdev-Ye-Kitaev (SYK) is a concrete solvable model with non-Fermi liquid behavior and maximal chaos. In this work, we study the entanglement Rényi entropy for the subsystems of the SYK model in the Kourkoulou-Maldacena states. We use the path-integral approach and take the saddle point approximation in the large-$N$ limit. We find a first-order transition exist when tuning the subsystem size for the $q=4$ case, while it is absent for the $q=2$ case. We further study the entanglement dynamics for such states under the real-time evolution for noninteracting, weakly interacting and strongly int…
We argue that in certain class of coupled Sachdev-Ye-Kitaev(SYK) models the low energy physics at large N is governed by a non-local action rather than the Schwartzian action. We present a partial analytic and extensive numerical evidence for this. We find that these models are maximally chaotic and have the same residual entropy as Majorana SYK. However, thermodynamic quantities, such as heat capacity and diffusion constant are different.
The search for a quantum theory of gravity has led to the discovery of quantum many-body systems that are dual to gravitational models with quantum properties. The perhaps most famous of these systems is the Sachdev-Ye-Kitaev (SYK) model. It features maximal scrambling of quantum information, and opens a potential inroad to experimentally investigating aspects of quantum gravity. A scalable laboratory realisation of this model, however, remains outstanding. Here, we propose a feasible implementation of the SYK model in cavity quantum electrodynamics platforms. Through detailed analytical and n…
A Generalization of Sachdev-Ye-Kitaev
SYK模型：费米子与$q$体，高斯随机，所有对所有的相互作用，是第一个迷人的新一类可解大$N$模型。我们将SYK推广到包括费米子的$f$风味，每个费米子占据$N_a$位点，并在相互作用中以$q_a$顺序出现。像SYK一样，这整个类别的模型一般都有一个红外固定点。我们计算了费米子的红外维数，以及单重双线性算符的谱。我们证明了在谱中总是存在一个二维算子，这意味着，与SYK一样，广义模型的红外四点函数中存在共形不变性的破坏和最大混沌.在无序平均之后，广义模型具有全局$O(N_1) \times O(N_2) \times \ldots\times O(N_f)$对称性：SYK的$O(N)$对称性的子群;从而给出更丰富的谱。我们还阐明方面的大$q$限制和OPE，并解决$q=2$ SYK在有限的$N$。
Tunable Quantum Chaos in the Sachdev-Ye-Kitaev Model Coupled to a Thermal Bath
Sachdev-Ye-Kitaev（SYK）模型描述了具有随机相互作用的Majorana费米子，它表现出许多有趣的性质，如非费米液体行为、量子混沌、涌现共形对称性和全息对偶。在这里，我们考虑一个SYK模型或SYK模型链的$N$马约拉纳费米子模式耦合到另一个SYK模型与$N^2$马约拉纳费米子模式，其中后者有更多的自由度，并发挥作用的热浴。对于一个单一的SYK模型耦合到热浴，我们表明，虽然李雅普诺夫指数仍然是成比例的温度，它单调下降，从$2π/β$（$β=1/(k_BT)$，$T$是温度）为零的耦合强度的热浴增加。对于一个链的SYK模型，当它们均匀地耦合到热浴，我们表明，蝴蝶速度显示交叉从$\sqrt{T}$ -依赖在相对较高的温度下的线性$T$ -依赖在低温下，与交叉温度也控制的耦合强度的热浴。如果仅SYK链的末端耦合到热浴，则该模型可以引入李雅普诺夫指数和蝴蝶速度两者的空间依赖性。我们的模型提供了规范的例子，在混沌模型的热化研究。
Instability of the non-Fermi liquid state of the Sachdev-Ye-Kitaev Model
研究了Sachdev-Ye-Kitaev（SYK）模型的一系列扰动。我们发现，由普通$q = 4$ SYK模型描述的混沌非费米液相具有轻微相关/无关（取决于耦合常数的符号）的对称性允许的四个费米子扰动。改变其中一个费米子微扰的符号会导致系统发生连续的混沌-非混沌量子相变，并伴随着自发的时间反演对称性破缺。从具有$q-$费米子相互作用的SYK $_q$模型开始，类似的扰动可以导致一系列新的相互作用共形场论不动点。
The Sachdev-Ye-Kitaev (SYK) model incorporates rich physics, ranging from exotic non-Fermi liquid states without quasiparticle excitations, to holographic duality and quantum chaos. However, its experimental realization remains a daunting challenge due to various unnatural ingredients of the SYK Hamiltonian such as its strong randomness and fully nonlocal fermion interaction. At present, constructing such a nonlocal Hamiltonian and exploring its dynamics is best through digital quantum simulation, where state-of-the-art techniques can already handle a moderate number of qubits. Here we demonst…
In arXiv:1707.02197, the authors considered the Sachdev-Ye-Kitaev model with quadratic perturbation (also known as mass-deformed SYK), and claimed that the quantum Lyapunov exponent would vanish in the regime of low temperature and small quartic coupling. We calculate the exponent exactly in that regime and show that it is nonzero.
Creating and probing the Sachdev-Ye-Kitaev model with ultracold gases: Towards experimental studies of quantum gravity
我们认为，全息原理，结合原子，分子和光学物理学的最新技术进展，可以导致量子引力的实验研究。作为一个具体的例子，我们考虑Sachdev-Ye-Kitaev（SYK）模型，它由自旋极化的费米子组成，具有全对全的复杂随机两体跳跃，并已被证明是一个特定的量子引力系统的对偶。如果全息对偶成立，那么实现SYK模型的低温态就被解释为实现了弦黑洞。我们介绍了SYK模型的一个变体，其中随机两体跳跃是真实的。该模型在大- $N$极限下与原始SYK模型等价。我们表明，该模型可以建立在原则上通过限制超冷费米子原子的光晶格和耦合两个原子与分子态通过光缔合激光。这一发展是朝着实验实现这种与量子黑洞对偶的系统迈出的重要的第一步。我们还展示了如何测量的SYK模型，它允许识别的最大混沌特性的黑洞的时间顺序的关联函数。
We study the SYK$_4$ model with a weak SYK$_2$ term of magnitude $Γ$ beyond the simplest perturbative limit considered previously. For intermediate values of the perturbation strength, $J/N \ll Γ\ll J/\sqrt{N}$, fluctuations of the Schwarzian mode are suppressed, and the SYK$_4$ mean-field solution remains valid beyond the timescale $t_0 \sim N/J$ up to $t_* \sim J/Γ^2$. Out-of-time-order correlation function displays at short time intervals exponential growth with maximal Lyapunov exponent $2πT$, but its prefactor scales as $T$ at low temperatures $T \leq Γ$.
Nucleation of Sachdev-Ye-Kitaev Clusters in One Spatial Dimension
研究Sachdev-Ye-Kitaev相互作用如何从一维系统中的局域单粒子态中产生，发现当局部相互作用投影到粗粒化局域轨道上时，耦合分布不同于标准SYK分布，而当将每个局域体积分解为M>1个微观部分时，耦合分布趋向复高斯SYK形式。
We study a description of the large N limit of the Sachdev-Ye-Kitaev (SYK) model in terms of quantum mechanics without quenched disorder. Instead of random couplings, we introduce massive scalar fields coupled to fermions, and study a small mass limit of the theory. We show that, under a certain condition, the correlation functions of fermions reproduce those of the SYK model with a temperature dependent coupling constant in the large N limit. We also discuss a supersymmetric generalization of our quantum mechanical model. As a byproduct, we develop an efficient way of estimating the large N b…
Single-Instance Observables in the Sachdev-Ye-Kitaev Model
本文提出SYK模型中低权重马约拉纳弦热期望值的图解展开，按N^{-1/2}幂次组织，可高效计算，并应用于MQ模型以提升热场双态保真度。
Energy diffusion and the butterfly effect in inhomogeneous Sachdev-Ye-Kitaev chains
在大$N$和强耦合极限下，计算了耦合Majorana Sachdev-Ye-Kitaev（SYK）模型的非齐次链的能量扩散常数$D$、Lyapunov时间$τ_{\text{L}}$和蝴蝶速度$v_{\text{B}}$.我们发现$D\le v_{\text{B}}^2 τ_{\text{L}}$从分析和数值方法相结合。我们的例子需要锐化假设的输运边界的基础上量子混沌。
Magic and Wormholes in the Sachdev-Ye-Kitaev Model
本文通过路径积分技术研究SYK模型热态中费米子弦期望值的统计性质，发现混沌情况下为高斯随机变量，可积情况下非高斯，并利用这些结果研究热态的魔法度量，同时在低温下通过引力对偶定量重现结果，其中方差与由算子弦对偶的粒子稳定的虫洞几何相关。
Disorder in the Sachdev-Yee-Kitaev Model
我们给出定性参数的Sachdev-Yee-Kitaev（SYK）模型的介观性质的全息制度与$q^2/N\ll 1$与$N$ Majorana粒子耦合的反对称和随机相互作用的范围$q$。使用随机变形的SYK模型，我们表明，其特征行列式服从粘性Burgers方程与小的光谱粘度在相反的制度与$q/N=1/2$，在领先的顺序。SYK模型的随机演化可以映射到随机矩阵理论，在边缘具有普遍的艾里振荡。的光谱流体动力学估计的集体模式的松弛。
We show that the low temperature phase of a conjugate pair of uncoupled, quantum chaotic, nonhermitian systems such as the Sachdev-Ye-Kitaev (SYK) model or the Ginibre ensemble of random matrices are dominated by replica symmetry breaking configurations with a nearly flat free energy that terminates in a first order phase transition. In the case of the SYK model, we show explicitly that the spectrum of the effective replica theory has a gap. These features are strikingly similar to those induced by wormholes in the gravity path integral which suggests a close relation between both configuratio…
The Sachdev-Ye-Kitaev (SYK) model is a model of $q$ interacting fermions whose large N limit is dominated by melonic graphs. In this review we first present a diagrammatic proof of that result by direct, combinatorial analysis of its Feynman graphs. Gross and Rosenhaus have then proposed a generalization of the SYK model which involves fermions with different flavors. In terms of Feynman graphs, these flavors can be seen as reminiscent of the colors used in random tensor theory. Applying modern tools from random tensors to such a colored SYK model, all leading and next-to-leading orders diagra…
The Sachdev-Ye-Kitaev (SYK) model describes electrons with random and all-to-all interactions, and realizes a many-body state without quasiparticle excitations, and a non-vanishing extensive entropy $S_0$ in the zero temperature limit. Its low energy theory coincides the low energy theory of the near-extremal charged black holes with Bekenstein-Hawking entropy $S_0$. Several mesoscopic experimental configurations realizing SYK quantum dynamics over a significant intermediate temperature scale have been proposed. We investigate quantum thermoelectric transport in such configurations, and descri…
We study a bipartite version of the Sachdev-Ye-Kitaev (SYK) model. We show that the model remains solvable in the limit of large-$N$ in the same sense as the original model if the ratio of both flavors is kept finite. The scaling dimensions of the two species can be tuned continuously as a function of the ratio. We also investigate the finite-size spectral properties of the model. We show how the level statistics differs from the original SYK model and infer an additional exchange symmetry in the bipartite model.
Local criticality, diffusion and chaos in generalized Sachdev-Ye-Kitaev models
Sachdev-Ye-Kitaev模型是一个$(0+1)$维模型，描述了具有随机相互作用的马约拉纳费米子或复杂费米子。该模型具有各种有趣的性质，如近似局部临界性（时间上的幂律相关性），零温度熵和量子混沌。在这篇文章中，我们提出了一个更高的维度推广的Sachdev-Ye-Kitaev模型，这是一个晶格模型与$N$马约拉纳费米子在每个网站和它们之间的随机相互作用。我们的模型可以定义在任意空间维度的任意格子上。在大的$N$极限下，高维模型保持了Sachdev-Ye-Kitaev模型的许多性质，如两点函数的局部临界性、零温度熵和无序关联函数测量的混沌.此外，我们获得了新的属性，如扩散能量传输和“蝴蝶速度”描述的混沌在空间中的传播更高的维度。我们主要给出了一个$(1+1)$维例子的结果，并在最后讨论了一般情况。
We prove non-perturbative bounds on the time evolution of the probability distribution of operator size in the $q$-local Sachdev-Ye-Kitaev model with $N$ fermions, for any even integer $q>2$ and any positive even integer $N>2q$. If the couplings in the Hamiltonian are independent and identically distributed Rademacher random variables, the infinite temperature many-body Lyapunov exponent is almost surely finite as $N\rightarrow\infty$. In the limit $q \rightarrow \infty$, $N\rightarrow \infty$, $q^{6+δ}/N \rightarrow 0$, the shape of the size distribution of a growing fermion, obtained by lead…
Quantum quench of the Sachdev-Ye-Kitaev Model
我们描述了费米子的Sachdev-Ye-Kitaev模型的非平衡动力学与所有的所有的相互作用。这些提供了没有准粒子激发的量子系统动力学的易处理模型。Kadanoff-Baym方程表明，最终状态是热的，其数值分析似乎与热化率成正比的最终状态的绝对温度。我们还得到了一个精确的解析解的非平衡动力学的大$q$极限的$q$费米子相互作用的模型：在这个限制，热化的费米子格林函数是瞬时的。
Supersymmetry is a powerful concept in quantum many-body physics. It helps to illuminate ground state properties of complex quantum systems and gives relations between correlation functions. In this work, we show that the Sachdev-Ye-Kitaev model, in its simplest form of Majorana fermions with random four-body interactions, is supersymmetric. In contrast to existing explicitly supersymmetric extensions of the model, the supersymmetry we find requires no relations between couplings. The type of supersymmetry and the structure of the supercharges are entirely set by the number of interacting Majo…
We provide an algorithm for preparing the thermofield double (TFD) state of the Sachdev-Ye-Kitaev model without the need for an auxiliary bath. Following previous work, the TFD can be cast as the approximate ground state of a Hamiltonian, $H_{\text{TFD}}$. Using variational quantum circuits, we propose and implement a gradient-based algorithm for learning parameters that find this ground state, an application of the variational quantum eigensolver. Concretely, we find quantum circuits that prepare the ground state of $H_{\text{TFD}}$ for the $q=4$ SYK model up to $N=12$.
Non-Stabilizerness of Sachdev-Ye-Kitaev Model
研究Sachdev-Ye-Kitaev模型的非稳定性，发现其Majorana谱呈高斯分布，具有更高的魔性。
We study a sparse Sachdev-Ye-Kitaev (SYK) model with $N$ Majoranas where only $\sim k N$ independent matrix elements are non-zero. We identify a minimum $k \gtrsim 1$ for quantum chaos to occur by a level statistics analysis. The spectral density in this region, and for a larger $k$, is still given by the Schwarzian prediction of the dense SYK model, though with renormalized parameters. Similar results are obtained for a beyond linear scaling with $N$ of the number of non-zero matrix elements. This is a strong indication that this is the minimum connectivity for the sparse SYK model to still h…
Sachdev-Ye-Kitaev Model as Liouville Quantum Mechanics
我们表明，适当列入软重新参数化模式的Sachdev-Ye-Kitaev模型的$N$随机相互作用马约拉纳费米子减少其长时间的行为，刘维量子力学。结果，所有零温度关联函数以普适指数$\propto τ^{-3/2}$衰减，衰减时间大于单粒子能级间距的倒数$τ\gg N\ln N$。在单粒子格林函数的特殊情况下，这种行为是零偏异常的表现，或能量的标度为$ε^{1/2}$。我们还提出了精确的对角化研究支持我们的结论。
In this work, we study a generalization of the coupled Sachdev-Ye-Kitaev (SYK) model with $U(1)$ charge conservations. The model contains two copies of the complex SYK model at different chemical potentials, coupled by a direct hopping term. In the zero-temperature and small coupling limit with small averaged chemical potential, the ground state is an eternal wormhole connecting two sides, with a specific charge $Q=0$, which is equivalent to a thermofield double state. We derive the conformal Green's functions and determine corresponding IR parameters. At higher chemical potential, the system …
We show that one can quantum simulate the dynamics of a Sachdev-Ye-Kitaev model with $N$ Majorana modes for time $t$ to precision $ε$ with gate complexity $O(N^{7/2} t + N^{5/2} t \,{\rm polylog}(N/ ε))$. In addition to scaling sublinearly in the number of Hamiltonian terms, this gate complexity represents an exponential improvement in $1/ε$ and large polynomial improvement in $N$ and $t$ over prior state-of-the-art algorithms which scale as $O(N^{10} t^2 / ε)$. Our approach involves a variant of the qubitization technique in which we encode the Hamiltonian $H$ as an asymmetric projection of a…
Motivated by recent works on atom-cavity realizations of fast scramblers, and on Cooper pairing in non-Fermi liquids, we study a family of solvable variants of the ($q=4$) Sachdev-Ye-Kitaev model in which the rank and eigenvalue distribution of the coupling matrix $J_{ij,kl}$ are tuneable. When the rank is proportional to the number of fermions, the low temperature behavior is sensitive to the eigenvalue distribution. We obtain a complete classification of the possible non-Fermi liquid quantum phases. These include two previously studied phases whose fermion scaling dimension depends continuou…
We give an exposition of the SYK model with several new results. A non-local correction to the Schwarzian effective action is found. The same action is obtained by integrating out the bulk degrees of freedom in a certain variant of dilaton gravity. We also discuss general properties of out-of-time-order correlators.
We present a review of the Sachdev-Ye-Kitaev (SYK) model of compressible quantum many-body systems without quasiparticle excitations, and its connections to various theoretical studies of non-Fermi liquids in condensed matter physics. The review is placed in the context of numerous experimental observations on correlated electron materials. Strong correlations in metals are often associated with their proximity to a Mott transition to an insulator created by the local Coulomb repulsion between the electrons. We explore the phase diagrams of a number of models of such local electronic correlati…
The Sachdev-Ye-Kitaev model spectral form factor exhibits absence of information loss in the form of a ramp and a plateau, that are typical of random matrix theory. In a large $N$ collective fields description, the ramp was reproduced by Saad, Shenker and Stanford \cite{Saad:2018bqo}, by replica symmetry breaking saddles for a connected component of the analytically continued to real times thermal partition function two point function. We derive a two sides Schwarzians effective action for fluctuations around the ramp critical saddles, by adapting to the two replica system a method by Kitaev a…
Quantum statistical mechanics of the Sachdev-Ye-Kitaev model and charged black holes
本文综述了Sachdev-Ye-Kitaev模型的热力学性质，揭示其无准粒子激发特征，并阐明其对理解无低能超对称带电黑洞低能态密度普适结构的贡献。
Strange metals and black holes: insights from the Sachdev-Ye-Kitaev model
本文综述了Sachdev-Ye-Kitaev模型如何作为可解的多粒子纠缠理论，为理解奇异金属和黑洞量子态提供现实普适模型与新洞见。
Competition between Chaotic and Non-Chaotic Phases in a Quadratically Coupled Sachdev-Ye-Kitaev Model
Sachdev-Ye-Kitaev（SYK）模型是研究非费米液体性质、全息对偶和极大混沌行为的一个具体的可解模型。在这项工作中，我们考虑的SYK模型，其中包含两个SYK模型与不同数量的马约拉纳模式耦合二次项的推广。该模型也是可解的，解显示了两个非费米液体混沌相之间的零温量子相变。这种相变是通过调节两个模数的比值来驱动的，并且费米液体非混沌相位于具有相等模数的临界点。在有限温度下，费米液相膨胀到有限状态。更有趣的是，一种不同的非费米液相在有限温度下出现。我们用谱函数、李雅普诺夫指数和熵来描述相图。我们的结果说明了两个非费米液相之间的量子相变和临界区的一个具体例子。
A folded string dual for the Sachdev-Ye-Kitaev model
本研究提出半径平方为虚数的刚性AdS₂中运动的折叠弦作为共形不动点处SYK模型的对偶，通过光锥坐标与Peierls括号描述系统，量子化后导出Pöschl-Teller方程并重现SYK算符谱。
A crucial result on the celebrated Sachdev-Ye-Kitaev model is that its large $N$ limit is dominated by melonic graphs. In this letter we offer a rigorous, diagrammatic proof of that result by direct, combinatorial analysis of its Feynman graphs.
Cooling the Sachdev-Ye-Kitaev model using thermofield double states
该研究提出一种利用两个SYK模型副本局域耦合构建绝热路径的实验协议，通过平滑调节耦合强度高效冷却SYK模型至低温引力区，数值验证其有效性并基于本征态热化提供微观解释，为强相互作用量子系统冷却提供新方案。
The existence of a quantum butterfly effect in the form of exponential sensitivity to small perturbations has been under debate for a long time. Lately, this question gained increased interest due to the proposal to probe chaotic dynamics and scrambling using out-of-time-order correlators. In this work we study echo dynamics in the Sachdev-Ye-Kitaev model under effective time reversal in a semiclassical approach. We demonstrate that small imperfections introduced in the time-reversal procedure result in an exponential divergence from the perfect echo, which allows to identify a Lyapunov expone…
Quantum simulation of the Sachdev-Ye-Kitaev model using time-dependent disorder in optical cavities
本文提出利用光学腔中的时间依赖性杂乱实现SYK模型的量子模拟方案，适用于多种杂乱模型的量子模拟。
Entanglement production in the Sachdev-Ye-Kitaev Model and its variants
通过冯·诺依曼纠缠熵研究SYK模型及其变体在有限马约拉纳费米子数下的纠缠动力学，发现早期线性增长、后期饱和至随机矩阵理论值，但增长率不同，归因于大N效应，并指出纠缠产生率可作为更精细的混沌探针。
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