Abstract Diffusion models have achieved state-of-the-art image synthesis, yet unlike GANs, they lack a well-structured latent space for intuitive image editing. Existing diffusion-based editing methods often rely on supervised fine-tuning or text-based guidance, while recent unsupervised techniques leveraging the model’s bottleneck layer suffer from one or more key limitations: (i) they focus only on global attributes, (ii) fail to disentangle local and global semantics, or (iii) require extensive human intervention. To fill this gap, we first propose an unsupervised method for localized image editing in pre-trained unconditional diffusion models that disentangles local and global semantics in the model’s latent space. Given an input image and a user-specified region of interest, our approach uses the denoising network’s Jacobian to map that region to a corresponding latent subspace. We then separate this subspace into shared (global) and region-specific components to uncover latent directions that control local attributes. These directions generalize across images, enabling semantically consistent edits without retraining. We go one step further by extending our method to minimize manual supervision by automatically inferring edit directions from a single reference image and generating region masks without human input. Experiments on multiple datasets show that our method yields more localized, high-fidelity edits than state-of-the-art approaches.

What do different contrastive learning (CL) losses actually optimize for? Although multiple CL methods have demonstrated remarkable representation learning capabilities, the differences in their inner workings remain largely opaque. In this work, we analyse several CL families and prove that, under certain conditions, they admit the same minimisers when optimizing either their batch-level objectives or their expectations asymptotically. In both cases, an intimate connection with the hyperspherical energy minimisation (HEM) problem resurfaces. Drawing inspiration from this, we introduce a novel CL objective, coined Decoupled Hyperspherical Energy Loss (DHEL). DHEL simplifies the problem by decoupling the target hyperspherical energy from the alignment of positive examples while preserving the same theoretical guarantees. Going one step further, we show the same results hold for another relevant CL family, namely kernel contrastive learning (KCL), with the additional advantage of the expected loss being independent of batch size, thus identifying the minimisers in the non-asymptotic regime. Empirical results demonstrate improved downstream performance and robustness across combinations of different batch sizes and hyperparameters and reduced dimensionality collapse, on several computer vision datasets.

Despite the considerable research output on Multimodal Learning for Affect-related tasks, most of the current methods are very complex in terms of the number of trainable parameters, and thus do not constitute effective solutions for real-life applications. In this work we try to alleviate this gap in the literature by introducing the Multimodal Attention Tensor Regression (MMATR) network, a lightweight model that is based on: (i) a static input representation (2D matrix of dimensions time × features) for each modality, which helps to avoid high-parameterized sequential models by incorporating a CNN, (ii) the replacement of the usual pooling and flattening operations as well as the linear layers by tensor contraction and tensor regression layers that are able to reduce the number of parameters, while keeping the high-order structure of the multimodal data, and (iii) a bimodal attention layer that learns multimodal co-occurrences. By a set of experiments comparing with a variety of state-of-the-art techniques, we show that the proposed MMATR can achieve results competitive to the state-of-the-art in the task of Multimodal Sentiment Analysis, albeit having four orders of magnitude fewer parameters.

Machine learning methodologies can be adopted in cultural applications and propose new ways to distribute or even present the cultural content to the public. For instance, speech analytics can be adopted to automatically generate subtitles in theatrical plays, in order to (among other purposes) help people with hearing loss. Apart from a typical speech-to-text transcription with Automatic Speech Recognition (ASR), Speech Emotion Recognition (SER) can be used to automatically predict the underlying emotional content of speech dialogues in theatrical plays, and thus to provide a deeper understanding how the actors utter their lines. However, real-world datasets from theatrical plays are not available in the literature. In this work we present GreThE, the Greek Theatrical Emotion dataset, a new publicly available data collection for speech emotion recognition in Greek theatrical plays. The dataset contains utterances from various actors and plays, along with respective valence and arousal annotations. Towards this end, multiple annotators have been asked to provide their input for each speech recording and inter-annotator agreement is taken into account in the final ground truth generation. In addition, we discuss the results of some indicative experiments that have been conducted with machine and deep learning frameworks, using the dataset, along with some widely used databases in the field of speech emotion recognition.