Can meditation stop breathing and heartbeat for a period of time?

The rise in body temperature triggers "clumsy fire" concentration, also called "spiritual heat". There are people who specialize in this method in Tibetan Buddhism.

Stop of external Qi, internal breath, and even qi pulse stagnation are phenomena of the Four Meditations and Eight Concentrations. You can check the relevant information, and it is not surprising. People who practice deeply have such experiences. It's not as miraculous as you imagine, it's just that there are too many people talking about theory now, and those who practice it don't want to show off, so you don't hear much, and it's just rare and strange.

In the first meditation, distracting thoughts will be reduced or disappeared. In the second meditation, the breath will stop breathing through the mouth and nose, and the fetal breath or body breathing will naturally enter. In the third meditation, the heart and pulse will stop beating. The state of neither thinking nor thinking.

The Four Zen and Eight Concentrations are Dharma, that is, Buddhism and paganism are the same. There are other qigong and other exercises that can also achieve the qi to stop the pulse, but they have nothing to do with Buddhism.

The Four Meditations and Eight Concentrations are not the core of Buddhism: the path to liberation.

If you only work hard on the physical body, you will not be able to achieve success until Maitreya becomes a Buddha. Therefore, not everyone who studies Buddhism has to go through this process. Most Buddhist practitioners do not follow the path of the Four Meditations and Eight Concentrations. Although it is not the core, it is indeed not easy to cultivate.

The core practices in Tibetan Buddhism include Dzogchen, Mahamudra, Yamantaka, etc. The rainbow transformation you mentioned is the verification of the achievements of Dzogchen "Tokar" practice.

The practice of Tuokar is based on the "complete" part, which is equivalent to Zen enlightenment and is a formless practice, and Tuokar is equivalent to the "upward" of Zen, that is, activation. Enablement is based on realization, and this is the true core of Buddhism - the path to liberation.

In Tibet, due to such customs, more emphasis is placed on verification. There are Honghua practitioners every year. You can also check the information yourself.

In the Mahayana of the Han Dynasty, magical powers were not valued, and some were even banned. These are all based on the root, but if you look at Zen classics, such as Wudeng Huiyuan, etc., there are no fewer great achievers who have manifested supernatural powers than those in Tibetan Buddhism. Modern eminent monks also have a certain number of months.

Buddhism lies in cultivating the mind, and how it is manifested depends on the practitioner's original wishes, causes and conditions, and the root of the teachings.

If you can enter Buddhism through this, you have a deep foundation and have cultivated it through predestined fate; if you are just seeking novelties and entangled in magical powers and mysteries, then I will fail in my interpretation of words.