There is no need to introduce a framework of string theory

For decades, most physicists thought string theory was the missing part between Einstein's general theory of relativity, which describes the laws of nature at the possible largest scale, and quantum mechanics, which describes the laws of nature at the possible smallest scale. However, an international collaborate team led by physicists from Radboud University has now provided convincing evidence that string theory is not the only theory to connect the two. They improved that, without introducing strings, it was possible to construct a theory of quantum gravity that obeyed by all the fundamental laws of physics. They reported their findings last week in the journal “Physical Review Letters”.

Although these two theories enable us to explain every physical phenomenon we can observe, it seems that there are unsolved conflicts between general relativity and quantum mechanics. All the fundamental forces other than gravity can be unified, but the quantization of gravity is difficult to conciliate.

No additional conditions

In the 1970s, physicists constructed a new set of physical theories to solve this problem, extending general relativity. According to so-called string theory, the most basic unit of the physical world is not a point particle, but a one-dimensional string that vibrates constantly. Since its inception, string theory has been the most extensive theoretical framework and is considered the most likely candidate for a unified theory.

However, now theoretical physicists at Radboud University have shown that string theory is not the only method. “We show that it is still possible to explain gravity purely in terms of quantum mechanics.”  The theoretical physicist Frank Saueressig said. “We have proved that the idea that everything is made up of point particles can still be adapted to quantum gravity without the intervention of strings. This particle physics framework has also been tested in experiments; such example is as the Large Hadron Collider (LHC) at CERN.

We see it in the experiment

“For scientists, this backup theory is attractive because string theory is difficult to prove by experiment. We only use principles that have been tested by experiments. In other words: No one has ever observed strings in an experiment, but particles are the matters that people could see at the LHC. This makes it easier for us to bridge the gap between theoretical predictions and experiments.”

There is only one set of laws

Now the team is applying their theory to black holes. “After all, nature only has one set of laws, and this set of laws could apply to various of questions which include what happens when particles collide at extremely high energies, what happens when particles fall into a black hole. It would be wonderful to be able to show that these irrelevant-looking problems are actually related, and thus solve both problems at the same time.”