• physics 17, 74
Most models of the overall shape and geometry of the universe, including some strange ones, are compatible with the latest observations of the universe.
Is the universe simply connected like a sphere, or does it contain holes or more complex structures like a donut? According to a collaboration of cosmologists, the topology of the universe—that is, its overall geometry—is still far from certain. Despite past claims that observations of the cosmic microwave background (CMB) ruled out various topologies, researchers believe that many of its shapes, including some strange ones, do not contradict the evidence. [1].
The overall geometry of the universe is thought to be determined by quantum processes that unfolded in the initial moments of the Big Bang. Identifying the topology of the universe will give researchers important clues about the nature of these quantum processes and could help them sift through many proposed theories of the early universe.
A given topology describes the connectivity of space and time. One of the possible non-trivial topologies of the universe is a 3-torus. To imagine, imagine twisting a cube by bending a pair of opposite sides until they face each other, and then gluing them together. Then imagine the same for the other two pairs. The line of sight that previously extended from the center of the cube to infinity will now return to the center of the cube through the closed loop.
ESA; Planck Cooperation
Closed loops also exist in other topologies that may describe the universe, and they may cause an optical illusion: the same part of the universe is observed in different parts of the sky. However, each topology has an associated length scale (such as the diameter of a closed loop), and if the length scale is too large, multiple views of the same cosmic neighborhood may not be obtained. The illusion may not occur because there may not have been enough time since the Big Bang for some light to reach us; in other words, the length scale may exceed the “cosmic microwave background horizon”, the distance to the oldest light source we can see .
All-sky maps of the cosmic microwave background from recent decades have provided detailed views of the young universe, but without any sign of repeating patterns (correlations) that might indicate closed loops. Ten years ago, the search for the topology of the universe in the cosmic microwave background seemed hopeless, if not over. Last year, however, an international group of cosmologists calling themselves the COMPACT Collaboration revived the quest. Now, in a first publication from COMPACT, researchers show that certain exotic topologies are actually consistent with observations of the CMB, and that, in fact, only a small subset of possible topologies have been explored so far.
Rather than considering all 18 mathematically possible topologies of Euclidean (flat) space, the COMPACT collaboration chose to focus on 3 toruses, called Second1and its two extensions, Second2 (180° twisted version Second1) and Second3 (90° twisted version Second1). Their reasoning is that if these relatively simple topologies are not ruled out, other more complex topologies may still be contenders.
According to cooperative calculations, 3-torus Second1 If its characteristic scale is smaller than the CMB horizon (as expected), the present observations exclude this phenomenon.But it turns out Second2 and Second3 Even though their scales are much shorter than the CMB horizon, they still play a role. That’s because their connection involves twists and turns. Looking at a region of the universe through a twisted closed loop yields two different but still related views. The next step in the collaborative agenda is to determine whether these correlations produce detectable topological fingerprints in the CMB.
Columbia University cosmologist Oliver Philcox agrees that the topology of the universe remains an open question. “There are many possible ways the universe is topologically connected, and it’s hard to rule them out,” he said.
charles day
Charles Day is the author of ” journal of physics.
refer to
- Y·Akrami et al. (COMPACT Collaboration), a commitment to searching for the topology of the universe in the future, physics. Pastor Wright. 132171501 (2024).
academic area
#topology #universe #simple
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