# Metaverse Architectures: A Comprehensive Systematic Review of Definitions and Frameworks
## 1 Introduction
Cloud computing facilitates the metaverse by ensuring continuous, rapid processing, reducing complexity, and decreasing power consumption [31]. Digital twins [32], which are digital replicas of real-world objects or systems, facilitate the modelling and analysis of actual phenomena, thereby enhancing the realism and functional complexity of metaverse experiences. 5G technology plays a crucial role in enabling the development and functionality of the metaverse and its associated applications [33]. The 5G network offers the necessary reliability, throughput, and latency, which are critical requirements for the metaverse [34]. Current technological advances and human behaviour shape the conceptualisation and definition of the metaverse [21; 35]. For example, the development of immersive hardware and the rise of 6G-enabled infrastructure are significantly shaping how the metaverse is conceptualised, enabling real-time, multisensory virtual experiences that blur the boundary between digital and physical worlds [23]. In parallel, changing human behaviours, such as increased virtual socialisation, demand for immersive experiences, and the normalisation of remote presence, are further driving the evolution of its definition [24]. However, the lack of agreement regarding the technologies that define the metaverse leads to definitional uncertainty, highlighting the necessity for a more precise conceptual framework in both academic and practical contexts [36]. The architectural form of the metaverse, much like its definition, is characterised by a lack of consensus due to the complexity and diversity of enabling technologies and its extensive range of applications [37]. The integration of diverse technologies, such as virtual reality, augmented reality, blockchain and artificial intelligence, necessitates distinct architectural requirements, each presenting specific design challenges [38]. Furthermore, the evolving nature of the metaverse contributes to the uncertainty in establishing a global framework. As these technologies advance, the foundational elements that define the metaverse continue to transform. The ecosystem is guided by short-term frameworks that respond to current conditions but may lack the capacity to provide the stability necessary for a comprehensive architectural standard [39]. Moreover, fundamental issues such as scalability and interoperability, inherent to the metaverse, further complicate security measures within its architecture [5; 40; 41]. The consideration of metaverse architecture is also complicated by conceptual disagreements among researchers and stakeholders. While some researchers promote centralised architectures with an emphasis on high-performance cloud computing to maintain sophisticated virtual environments, others support decentralised approaches that use blockchain technology to provide heightened security and privacy [36; 42]. In addition, the lack of a shared terminology and comprehensive discourse on the building blocks of metaverse architecture also contributes towards disparate interpretations on metaverse architecture, thus denoting potential shortcomings within current literature and concerted research attempts [43]. In addition, the industry-specific use cases of the metaverse complicate the architectural landscape. Special requirements and functions demand specialised architectural frameworks designed for particular environments [44; 45]. For example, a metaverse platform has been developed to support the preservation of intangible cultural heritage [46], while another conceptual framework has been proposed to transform cardiovascular healthcare through immersive technologies [47]. As a result, numerous architectures have emerged, each addressing different needs, yet none have achieved global acceptance [48; 49; 50]. The following parts of this paper are structured as follows. The methodology for identifying and analysing metaverse definitions and architectures through a systematic literature review and hybrid thematic analysis is detailed in Section 2.