現在、ハーバード大学物理学教授。プリンストン大学物理学部で終身在職権（tenure）をもつ最初の女性教授となる。また、マサチューセッツ工科大学およびハーバード大学においても理論物理学者として終身在職権をもつ初の女性教授となる。
ブレーンワールド（膜宇宙、braneworld）またはブレーン宇宙論（brane cosmology）とは、『我々の認識している4次元時空（3次元空間+時間）の宇宙は、さらに高次元の時空（バルク（bulk））に埋め込まれた膜（ブレーン（brane））のような時空なのではないか』と考える宇宙モデルである。低エネルギーでは（我々自身を含む）標準模型の素粒子の相互作用が4次元世界面（ブレーン）上に閉じ込められ、重力だけが余剰次元（5次元目以降の次元）方向に伝播できる、とする。
ブレーンワールド理論とは、宇宙が私たちが普段知っているような3次元空間ではなく、4次元以上のより高次元空間に広がっている可能性があるという仮説です。
具体的には、ブレーンワールド理論では、我々が知る3次元空間を含む大きな宇宙の中に、2つの「膜」（ブレーン）が存在すると考えられます。我々が住む宇宙は、そのうちの1つのブレーン上に存在しているとされています。もう1つのブレーンは、我々が知覚できない別の空間に存在しているとされています。
ブレーンワールド理論によれば、重力や他の力は、3次元空間上で働くわけではなく、ブレーン同士の相互作用によって生じるとされています。また、ブレーン同士が接触するときには、エネルギーが放出されることが予想されています。このエネルギーがビッグバンのような現象を引き起こす可能性があるとされています。
ブレーンワールド理論は、超弦理論や量子重力理論などと組み合わせることで、宇宙全体を説明するための新しい枠組みとして注目されています。また、ブラックホールや宇宙膨張、宇宙の構造などに関する疑問を解決するためにも、重要な理論とされています。
ブレーンワールド理論は、我々が知っている4次元の時空（3次元空間+時間）が、さらに高次元の時空（バルク）の中に存在する膜（ブレーン）のようなものであるという考え方に基づいています。この理論では、我々が経験する現象は、我々自身を含む標準模型の素粒子の相互作用が4次元世界面（ブレーン）上に閉じ込められているために説明できるとされています。一方、余剰次元（5次元目以降の次元）は重力だけが伝播できるとされています。
ブレーンワールド理論は、多次元宇宙論の一つであり、標準的な宇宙論モデルに対するアプローチの一つです。この理論は、現象学的に観測されている重力の強さが、標準理論では説明できないとされている問題に取り組むために提案されました。また、ブレーンワールド理論は、超弦理論やM理論などのような新しい理論を統合するためにも用いられています。
リサ・ランドール、若田光一『リサ・ランドール 異次元は存在する』日本放送出版協会〈NHK未来への提言〉、
『ワープする宇宙』
ワープする宇宙―5次元時空の謎を解く
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ひも理論は違う。これは純粋に理論上の疑問と着想にもとづいていて、まだ数学的に完全に定式化されてもいないから、その予言についても、確たることは何も言えない。
一つの次元があることに気づく。このときから、物理法則は── もちろん常識も── 人に「次元は三つだ」と信じこませ、それ以上の次元があるとは夢にも思わせなくする。 だが、時空はそうして思い描いてきた姿とは驚くほど違っている可能性がある。これまでにわかっている物理法則のなかで、空間に三つしか次元がないと断定できるものはない。別の次元── 余剰次元── が存在している可能性を検討もしないうちに切り捨ててしまうのは、性急にすぎると言えるかもしれない。「上下」が「左右」や「前後」とは別の方向であるように、まったく新しい別の次元が私たちの宇宙に存在していたとしてもおかしくはない。実際に目で見たり、指先で感じたりはできない。
余剰次元がかたる。
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Currently Professor of Physics at Harvard University. She will be the first female professor of physics at Princeton University to hold a tenure. She also becomes the first female professor to hold tenure as a theoretical physicist at the Massachusetts Institute of Technology and Harvard University.
Braneworld (membrane universe, brane cosmology) means that "our perceived four-dimensional space-time (three-dimensional space + time) universe is a higher-dimensional space-time (bulk). ) is a space-time like a membrane (brane) embedded in the space model. At low energies, the interaction of standard model particles (including ourselves) is confined to the 4-dimensional world plane (brane), and only gravity can propagate in the extra dimensions (fifth dimension and beyond). .
The brain world theory is the hypothesis that the universe may not be a three-dimensional space as we usually know, but may extend into a higher-dimensional space of four or more dimensions.
Specifically, in the brane world theory, it is thought that there are two "membrane" (branes) in the big universe including the three-dimensional space that we know. The universe we live in is said to exist on one of these branes. Another brain is said to exist in another space that we cannot perceive.
According to braneworld theory, gravity and other forces do not act in three-dimensional space, but are caused by interactions between branes. Also, energy is expected to be released when the brains come into contact with each other. It is believed that this energy can cause phenomena like the Big Bang.
Braneworld theory is attracting attention as a new framework for explaining the entire universe by combining it with superstring theory and quantum gravity theory. It is also considered an important theory for solving questions about black holes, the expansion of the universe, and the structure of the universe.
The brane world theory is based on the idea that the 4-dimensional space-time (3-dimensional space + time) that we know is like a membrane (brain) that exists in a higher-dimensional space-time (bulk). I'm here. According to this theory, the phenomena we experience can be explained by the interaction of standard model particles, including ourselves, confined to a four-dimensional world plane (brane). On the other hand, it is said that only gravity can propagate in extra dimensions (dimensions after the 5th dimension).
Braneworld theory is a multidimensional cosmology and an approach to standard cosmological models. This theory was proposed to address the problem that the phenomenologically observed strength of gravity cannot be explained by the Standard Model. Braneworld theory is also used to integrate new theories such as superstring theory and M-theory.
Lisa Randall, Koichi Wakata "Lisa Randall: Another Dimension Exists" Japan Broadcasting Publishing Association <Proposals for the Future of NHK>,
"Warping Universe"
"Lisa Randall: Another Dimension Exists" is a printed version of "Proposals for the Future" and is less than 100 pages long. Mainly a dialogue with astronaut Koichi Wakata, he conveys the contents of "The Warping Universe" concisely. Life history is told until it reveals its head.
"Warping Universe" puts the story of an 11-year-old girl named Athina at the beginning of each chapter and uses it as a pillow. Athena is guided by a future person named Ike Rushmore 42 who came to the present age in a time machine, and experiences the wonders of 5D space-time in "Alice's Adventures in Wonderland". It is a Randall-like taste that she loves Lewis Carroll.
Randall's five-dimensional theory is a kind of extra-dimensional theory, but the extra-dimensional theory came out of string theory. In string theory, all things are considered to be minute strings that vibrate, but if you vibrate a string in three dimensions, the amplitude will spread to the scale of the universe, so we consider vibrations in 10 dimensions of space-time (9 dimensions + time). It is said that the vibration of 10-dimensional space-time can be controlled neatly, but three types of string theories have been created. After that, we found that the three types of string theories can be understood in a unified way by increasing the dimension by one and considering an 11-dimensional space-time. This is called M-theory. The three string theories in 10-dimensional spacetime are special cases of M-theory in 11-dimensional spacetime.
It can be 10 or 11 dimensions, but we can only perceive the three dimensions of length, width, and height. Even if you add time, it is only four dimensions. What about the remaining dimensions—the extra dimensions?
The answer of string theory is that the extra dimensions have shrunk to the microscopic world.
"I want you to think about straws." When viewed from a distance, the straw looks like a straight line, but if you take a close look at it, you will see that it is cylindrical and has another dimension of circumference in addition to its length. The extra dimensions are hidden like the circumference of a straw.
"I don't know if there really are extra dimensions." Whether it's 10-dimensional or 11-dimensional, it's just a matter of convenience in mathematics that if you think about it that way, the formula will come together neatly, and it's not been proven. No one has ever won a Nobel Prize for string theory.
The article explaining the shrunken extra dimensions is brilliant. Randall uses Newton's law of universal gravitation as an example to explain that even 9 dimensions + time or 10 dimensions + time can be regarded as 3 dimensions + time. The gravitational force is inversely proportional to the square of the distance. The distance is squared because the watered area increases squarely. The more area that is watered, the sparse the water becomes. Similarly, gravity also weakens in inverse proportion to the square of the distance.
If the extra dimensions hadn't shrunk, gravity would have weakened sharply with the distance to the 8th or 9th power.
"I've never read an explanation like this before." Moreover, this description is a foreshadowing of the fifth-dimensional theory that explains why gravity is orders of magnitude weaker than the other three forces.
There is a reason why "Warping Universe" is so long. If you're tired of enlightenment books that look like whipped cream and sugar, then this book is for you. Randall must be first class as a teacher.
Warping Universe: Solving the Mystery of 5-Dimensional Space-Time
Lisa Randall
String theory is different. Since it is based purely on theoretical questions and ideas, and has not yet been fully formulated mathematically, nothing can be said with certainty about its predictions either.
She realizes that there is one dimension. From that moment on, the laws of physics--she, of course, common sense--make people believe that there are three dimensions, and not dream of any more. However, there is a possibility that space-time will be surprisingly different from what you have envisioned. None of the known laws of physics can assert that space has only three dimensions. It might be said that it is too hasty to discard the possibility that there is another dimension-- surplus dimension-- without even considering it. Just as "up and down" is a different direction than "left and right" and "back and forth", it would not be surprising if a completely new dimension existed in our universe. You can't actually see it with your eyes or feel it with your fingertips.
Extra dimensions are needed.
A warping universe Solve the mystery of 5-dimensional space-time
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