Fig. 7
Wavelet coherence heat maps. BTC: Bitcoin, XAU: Gold, JPN: Nikkei 225, SPX: S&P 500, UK: FTSE 100, CHN: China A50, DEU: DAX and CAC: CAC 40. In this Figure, the horizontal axis delineates the timeline by years, while the vertical axis measures time in days, signifying the time horizon. Longer time horizons are indicated by lower positions along the vertical axis, denoting a more extended period. Time intervals of approximately 1–16 days are classified as short-term, whereas values exceeding 16 days pertain to the long-term perspective. Each heatmap provides a visual representation of the intricate interplay between Bitcoin and a distinct variable, such as gold and stock markets, as explicitly designated in the heading of each heatmap. Upward-pointing arrows (↑) and diagonal arrows (↘ and ↖) serve as indicators of Bitcoin's pivotal role as the leading influencer in the contagion dynamics between itself and the specific variable under scrutiny. This implies that the transmission of contagion is predominantly instigated by Bitcoin, affecting the other variable. In contrast, downward-pointing arrows (↓) and reverse diagonal arrows (↗ and ↙) imply that the other variable, whether it be gold or the stock markets, assumes the primary role in driving the contagion relationship between itself and Bitcoin. In such instances, the contagion predominantly originates from these variables, impacting Bitcoin. Right-pointing arrows demonstrate a positive relationship between Bitcoin and gold or stock markets, whereas left-pointing arrows indicate an inverse relationship. The black lines in the heat maps represent statistically significant relationships at a 5% level of significance. Cooler colors (blue) reflect a weaker contagion between the variables, whereas warmer colors (red) indicate a stronger contagion