## Holographic Universe: The relationship between entropy and information in the Cosmic Cycle -- Dr. Ding Ru

2021-08-03

Introduction: University of Waterloo astrophysicist Afshordi and his team reported in 2017 that they had studied the fluctuations in the cosmic microwave background and found strong evidence to support a holographic interpretation of the early universe. "If you think about it, everything we see, feel, hear, and feel about time is actually a flat two-dimensional field," said team member Costas of the University of Southampton in the UK. A two-dimensional surface contains the encoding of a three-dimensional image, a bit like the security chip in a credit card that contains a lot of information. But this time it's the whole universe."

1. Holographic universe

The so-called hologram, that is, all information, originally refers to the two-dimensional photo plate on the record of all the information of three-dimensional objects. Whereas the usual photographic plate records only the intensity of light, holograms record not only the intensity but also the phase of light, so coherent light can be used to extract all the geometric information about three-dimensional objects. But did it ever occur to you that our universe is also a hologram? To say that the universe is a hologram means that the universe has properties similar to a hologram. The discovery comes from the study of black hole physics. Black holes are a special class of objects whose gravity is so strong that even light is attracted to them. So a black hole is black and people can't see it. Mathematically, black holes refer to a special class of solutions to the gravitational field equations of Einstein's general relativity, a region of space-time whose boundary is called the event horizon. Anything that crosses the event horizon into the black hole cannot return to the outside world. So the event horizon of a black hole is a unidirectional membrane that separates the inside and outside of the black hole.

Figure 1

In 1915, Einstein discovered that gravity does not actually exist in nature, but is actually the effect of the bending of space-time. Einstein's general theory of relativity, which links the curvature of space and time to the distribution of matter in space and time, contains rich philosophical ideas. In explaining Einstein's general theory of relativity, the famous physicist Wheeler once said, "Matter in space-time tells space-time how to curve, and curved space-time tells matter how to move within it." The famous theoretical physicist Landau once described general relativity as "probably the most beautiful theory".

In 1973, Bekenstein discovered that a black hole must have entropy, or physical processes involving black holes would violate the second law of thermodynamics (the law of entropy increase). He showed that the entropy of a black hole must be proportional to the area of the black hole's event horizon. In 1974, Hawking proved that black holes are not black at all, and that a black hole radiates energy outward in the form of blackbody thermal radiation, whose temperature is proportional to the gravitational pull on the black hole's surface. Bekenstein, Hawking and others proved that the black hole is actually a thermodynamic system, it has mass, temperature, entropy and other thermodynamic quantities, these thermodynamic quantities meet the three laws of thermodynamics.

The entropy of a system is a description of its microscopic degrees of freedom. In thermodynamic statistical physics, entropy is an extended quantity, that is, it is proportional to its volume: the greater the volume of a system, the greater its entropy. A black hole's entropy is proportional to its surface area, not its volume. This special property implies a profound connotation, which reveals that gravity has a special property - holography. The concept that gravity has holographic properties was proposed in 1993 by The Nobel Prize winner In physics, Terhoft. In 1994, Stanford University physicist Joseph Saskand elaborated on this idea. The holographic nature of gravity means that the effective degree of freedom of a gravitational system is proportional to the surface of the system, as if distributed on the surface. If so, our universe would be a hologram whose degrees of freedom (all its properties, including its dynamics) could well be described on a holographic screen.

The first beautiful example of realizing the holographic principle of gravity was proposed by Maldacina in superstring theory. At the end of 1997, through the study of the soliton perturbation superstring theory (D - film), the properties of Mr. Darcy that found in an anti-de sitter (Ad) S space-time (category with a cosmological constant Einstein gravitational field equation solution) on the theory of quantum gravity is equivalent to the anti-de sitter spacetime boundary conformal field theory (CFT is). This is called Ad S/CFT duality. Later, the famous superstring theorists witten et al constructed a mathematical relationship between the theory of quantum gravity in anti-de Sitter space-time and the conformal field theory on anti-de Sitter boundaries. This relationship is sometimes called the Ad S/CFT duality dictionary because it maps the one-to-one correspondence between the two theories.

Figure 2. A map of the cosmic microwave background radiation from the Planck satellite

2. Vibration of the string

String theory is that all of the particles in micro dimensional time and space by a vibrating string, the string to be able to pull to god, twisting and bending, in fact, although string is fine, but they are hard to imagine the toughness, huge tension makes them unable to stretch to our can be observed, the length of the elementary particles of string is the smallest scales in the universe - the Planck length. Different particles of elementary particles and forces of virtual particles are composed of the same string, the difference is string vibration mode, and the vibration of the string is not confined to the best of our knowledge of the four dimensional space-time, after a string theorists of precise calculation, also need the other seven dimensions to meet the vibration of the string, we can't see these curled up in the four-dimensional spacetime dimensions, Again like a thick wool also too small too thin for us, of course not online any exercise, but for a small number of flying insects, they can easily walk in wool on the cylinder, any objects smaller than small flying insects can even pass by on the wool potholes, found online smaller dimensions.

So elementary particles circle of small string like themselves composite propeller, when we use a slow shutter speed to capture, at this moment is the basic particle of the size of a point, do not see any structure, constantly increase the shutter speed, now you will find some string loop state will slowly emerge, with the increase of the shutter speed, The vibrations of each part of this loop hidden in the curled dimensions are revealed, and this new image looks more chaotic and spread out over a larger area, and will continue to spread out over the entire universe.

If you can't increase the shutter speed, another way to see the structure of the string is to slow it down: When a tiny particles near the event horizon, the velocity of the particles due to the tremendous gravity are getting slower and slower, as a growing number of vibrating string structure can raise the outside observer's line of sight, and with the passage of time, the original structure is more and more small particles of propeller and pervading the whole horizon slowly, But when the observer is falling with the particle, because they are in the same situation, they do not notice that their own motion and that of the falling particle are slowing down, and there is no visual change. The particle is still the same tiny particle. So string theory makes Saskand's theory of black hole complementarity a little less weird, and the two completely different results are just different observers in different frames of reference.

3. Black Holes Have hair

Another important addition to the theory of black hole complementarity is that string theory breaks down John Wheeler's conclusion that black holes have no "hair" and describes in a more intuitive way how the information being sucked in eventually escapes from the black hole.

Black hole without the conclusion of "hair" hawking, 1973, et al. proposed no Mao Dingli black holes, they thought into the black hole information, whether it's a tree or a person, will only rest mass, charge and three angular momentum, the rest of the elements such as composition, temperature and radiation, and so on other information are not preserved, so a black hole is "naked", is a simple, It's smooth. For Hawking, once you know its mass, angular momentum, and charge, you know everything about the black hole. This is called the black hole hairless theorem. According to string theory, black holes don't look that simple. The image of the black hole's event horizon is a mass of strings that have been gravitationally flattened to the surface. These strings are tightly wound and produce quantum perturbations that cause anyone outside the black hole to see many string fragments popping up on the surface of the event horizon, each with its end firmly fixed to the horizon. String theory calculates that two fundamental strings can pass through each other and reassemble, which is consistent with the uncertainty of the quantum world. There is a 90% chance that two strings, or different parts of the same string, will meet and pass through each other without accident, and a 10% chance that they will reassemble and form a new complete string coil. So dew outside the event horizon of the piece of string has a 10% chance of restructuring into a new string ring, a new particle, and dropped down from the horizon to leave the danger zone, when the particle to escape from a black hole, the energy of black holes has been reduced, it is more clearly explain the hawking radiation and evaporation of the black hole.

4. Information is hidden in the folds of the shell

(1) The code in the fold

Through on the face of string theory is introduced, we found that in the space of the human eye can't see there is a more multidimensional space and time, the time and space curled distribution at each point of the space, most basic string in curled up in the dimension of space and time constant winding and vibration of the huddle of multidimensional space and time can also be referred to as we are now in the fold of space and time.

In life, you can never find a perfectly smooth object, every object has wrinkles, and in string theory, the folds of extended four-dimensional space-time are the other seven curled dimensions. Hawking in the universe in a nut shell, also said that the universe is a massive and small volume, like fruit shell of space and time, the quantum fold of fruit shell contains all the information in the universe, the big bang is the process of the quantum of the packets in fold divide replication process, which contains the whole information of each part, the part also carries all the information in the overall, The code for carbon atoms, for example, has been stored in the folds of fruit shells since the early days of the Big Bang, and carbon atoms are still there in their original structure.

(2) Mutual transformation of order and disorder

At the beginning of the shells in the universe, everything is so highly ordered, so that it is in a highly unusual low entropy state, in the continuous replication and division information to generate new material at the same time, the total entropy is increasing, order began to slowly towards disorder, this kind of highly ordered decision the initial state of the universe will follow the second law of thermodynamics, which towards the direction of entropy. When a page - numbered book is thrown into the air, page by page, to examine the scattered pages, you must find that the pages are confused. Why should you be so sure? Because the book starts out in a highly ordered state, its pages are coded with zero entropy, so it can only go in the direction of increasing entropy and confusing information. But what if the pages were messed up in the first place? Will the scattered page code be discovered at a glance even if it is shuffled again? The answer is no: the entropy of the two is about the same. So, because the universe was born in a highly ordered state, we've been living in a highly entropy universe ever since.

But is there only a one-way transition from order to disorder in the universe? Of course not, like any two contradictory relations, order and disorder are opposite and unified, and will also be transformed into each other under certain conditions. As is known to all, the premise of the second law of thermodynamics was founded is in an isolated system, but in the real universe is almost impossible to find a completely isolated existence system, information and information, between object and object, system and system always interrelated and interwoven, formed each open system far from equilibrium state, and continuously through the exchange of matter and energy with the outside world, Thus, under certain conditions, disorder is transformed into order, which is the dissipative structure theory of famous physicist, Ilya Puigozin. Life system is a typical open system, and are far from equilibrium state dissipative structure, its important characteristics is must constantly with the surrounding environment for the exchange of material, energy and entropy, resulting in a negative entropy flow system to make itself the sum of the total entropy of unchanged or even reduced, form an orderly structure in order to maintain the survival and evolution of life, this also is the process of metabolism of life system.

Schrodinger, in his book What Is Life, argues that the only way for life to escape death, the maximum entropy, is to continuously absorb negative entropy from the outside world. The isolated system always tends to the disordered information, and it is this inner law that causes the open system such as living body to continuously transfer entropy with the external environment, so as to realize the order in the disordered, and the inner order of the system must be at the cost of the overall disorder and entropy increase.