Rumors on social media can spread rapidly and widely with the help of the Internet characteristics, causing serious negative impacts on social stability and public life. In order to distinguish rumors from non-rumors, most of the existing methods are based on neural units to encode and observe the content of claims, user comments and rumor propagation patterns. However, these methods only consider the event context information in a single conversation thread, ignoring the public opinion (global contextual information) corresponding to the event in the external news environment. Be aware that users are easily distracted by opinion leaders to false facts and induced to make supportive replies on false claims. In order to address the above-mentioned limitation, we propose a Global Structural-Temporal Graph Network (GSTGN) framework. Specifically, we first construct a multi-modal global opinion graph based on the conversation threads belonging to the same event to capture the external public opinion of the target event. Then to enhance representation learning, we design a Structural-Temporal (ST) unit to encode structural and temporal features of the local conversation graph, and utilize the structural feature of the local graph to guide the learning and encoding of the global opinion graph. Experimental results on two public benchmark datasets prove that our GSTGN method achieves better results than other state-of-the-art models.

With more and more messages in the form of text and image being spread on the Internet, multi-modal rumor detection has become the focus of recent research. However, most of the existing methods simply concatenate or fuse image features with text features, which can not fully explore the interaction between modalities. Meanwhile, they ignore the convergence inconsistency problem between strong and weak modalities, that is, the dominant rumor text modality may inhibit the optimization of image modality. In this paper, we investigate multi-modal rumor detection from a novel perspective, and propose a Multi-modal Graph Interactive Network with Adaptive Gradient (MGIN-AG) to solve the problem of insufficient information mining within and between modalities, and alleviate the optimization imbalance. Specifically, we first construct fine-grained graph for each rumor text or image to explicitly capture the relation between text tokens or image patches in uni-modal. Then, the cross modal interaction graph between text and image is designed to implicitly mine the text-image interaction, especially focusing on the consistency and mutual enhancement between image patches and text tokens. Furthermore, we extract the embedded text in images as an important supplement to improve the performance of the model. Finally, a strategy of dynamically adjusting the model gradient is introduced to alleviate the under optimization problem of weak modalities in the multi-modal rumor detection task. Extensive experiments demonstrate the superiority of our model in comparison with the state-of-the-art baselines.

Rumors spread through the Internet, especially on Twitter, have harmed social stability and residents’ daily lives. Recently, in addition to utilizing the text features of posts for rumor detection, the structural information of rumor propagation trees has also been valued. Most rumors with salient features can be quickly locked by graph models dominated by cross entropy loss. However, these conventional models may lead to poor generalization, and lack robustness in the face of noise and adversarial rumors, or even the conversational structures that is deliberately perturbed (e.g., adding or deleting some comments). In this paper, we propose a novel Graph Adversarial Contrastive Learning (GACL) method to fight these complex cases, where the contrastive learning is introduced as part of the loss function for explicitly perceiving differences between conversational threads of the same class and different classes. At the same time, an Adversarial Feature Transformation (AFT) module is designed to produce conflicting samples for pressurizing model to mine event-invariant features. These adversarial samples are also used as hard negative samples in contrastive learning to make the model more robust and effective. Experimental results on three public benchmark datasets prove that our GACL method achieves better results than other state-of-the-art models.

Quantum neural network (QNN) is developed based on two classical theories of quantum computation and artificial neural networks. It has been proved that quantum computing is an important candidate for improving the performance of traditional neural networks. In this work, inspired by the QNN, the quantum computation method is combined with the echo state networks (ESNs), and a hybrid model namely quantum echo state network (QESN) is proposed. Firstly, the input training data is converted to quantum state, and the internal neurons in the dynamic reservoir of ESN are replaced by qubit neurons. Then in order to maintain the stability of QESN, the particle swarm optimization (PSO) is applied to the model for the parameter optimizations. The synthetic time series and real financial application datasets (Standard & Poor's 500 index and foreign exchange) are used for performance evaluations, where the ESN, autoregressive integrated moving average (ARIMAX) are used as the benchmarks. Results show that the proposed PSO-QESN model achieves a good performance for the time series predication tasks and is better than the benchmarking algorithms. Thus, it is feasible to apply quantum computing to the ESN model, which provides a novel method to improve the ESN performance.