Reports indicate positive sentiment for NVIDIA, with its efforts seemingly allaying fears of an artificial intelligence (AI) bubble in the Japanese tech market. The technology and graphic processing unit (GPU) giant NVIDIA has managed to maintain a strong foothold in the market, despite concerns over whether the rapidly growing AI sector has become a speculative bubble. Timing and additional factors aren't explicitly mentioned in the headline and would require more context for clarity.

Japan has been deeply invested in the AI technology sector, seeing it as a central pillar for economic growth. As such, the nation eyes fluctuations and advancements in this sphere with keen interest. Concerns about an AI bubble signal worries about the potential overvaluation of AI businesses and the implications of a possible burst. In that sense, NVIDIA's performance acts as a barometer for broader market sentiments.

The tech and AI markets are global, with large companies like NVIDIA influencing sentiment far beyond their home base in the U.S. Similar concerns about the sustainability and value of the AI and tech market are prevalent in the U.S and EU. However, interpretations and reactions to market fluctuations may vary based on regional factors such as economic policies and technological advancement rates.