Didicosm Explained

Didicosm
Author:Greg Egan
Country:Australia
Language:English
Genre:Science fiction
Published In:Interzone
Publication Type:Periodical
Publisher:TTA Press
Media Type:Print
Pub Date:July/August 2023

"Didicosm" is a science-fiction short story by Australian writer Greg Egan,[1] first published in Analog in July/August 2023.[2]

Plot

As a child, her father shows Charlotte the night sky and wants her to realize the truth about the endless worlds and possibilities in the universe. In one of his books, he read about the idea of the universe repeating, but with changes occurring and later uses this thought to rationalize his own suicide. After her mother dies as well, Charlotte is brought to her grandmother and later wants to find the correct topology of the universe, which turns out to be a didicosm (Hantzsche-Wendt manifold). Her own student later comes up with a theoretical explanation involving quantum gravity, concluding this shape is indeed canonical due to being the only platycosm with a finite first homology group. Charlotte returns to her partner thinking that she lives in the best possible universe.[3]

Background

While the 3-torus (

T3=R3/Z3

), also one of the ten platycosms, can be depicted as space-filling repetition of the exact same cube with same orientation (hence a cube with respective opposite sides identified with same alignment), the didicosm can be depicted as a chessboard-like filling featuring cubes flipped and turned upside down.[4] Both illustrations are featured in the short story. In 1984, Alexei Starobinsky and Yakov Zeldovich at the Landau Institute in Moscow proposed a cosmological model where the shape of the universe is a 3-torus.[5]

The first homology of the didicosm is

2
Z
4
. (For the 3-torus it is

Z3

.) The derivation is explained by Greg Egan on his website, which also lists four academic papers taken for the scientific basis of the short story: „Describing the platycosms“ by John Conway and Jean-Paul Rossetti,[6] „The Hantzsche-Wendt Manifold in Cosmic Topology“ by Ralf Aurich and Sven Lustig,[7] „On the coverings of the Hantzsche-Wendt Manifold“ by Grigory Chelnokov and Alexander Mednykh[8] as well as „How Surfaces Intersect in Space“ by J. Scott Carter.

Reception

Reviews

Sam Tomaino, writing for SFRevu, thinks that the short story „gets a little technical but [has] an interesting idea“.[9] [10]

Mike Bickerdike, writing for Tangent Online, states that "Didicosm" is "somewhat unusual as an SF short story, because while it is technically a story, it is more a speculation on whether Hantzsche–Wendt manifolds apply in cosmological topology." He claims that "there is a story here, but it is rather weak, and serves only as a vehicle" for the main idea, which is an "impenetrable subject for those [....] who lack a higher degree in theoretical physics or the relevant mathematics."[11]

Awards

The short story was a finalist for the Analog Analytical Laboratory (AnLab) Award for best novelette in 2023.[12] [13]

External links

Notes and References

  1. Web site: Summary Bibliography: Greg Egan . 2024-04-19 . en.
  2. Web site: Title: Didicosm . 2024-04-19 . en.
  3. Web site: Greg Egan . 2023-06-17 . Didicosm . 2024-04-19 . en.
  4. Web site: Greg Egan . Didicosm: Loops Across Space . 2023-10-20 . en.
  5. Overbeye, Dennis. New York Times 11 March 2003: Web. 16 January 2011. “Universe as Doughnut: New Data, New Debate”
  6. Web site: John Horton Conway, Juan Pablo Rossetti . 2003-11-26 . Describing the platycosms . 2023-10-21 . en.
  7. Web site: Ralf Aurich, Sven Lustig . 2014-03-10 . The Hantzsche-Wendt Manifold in Cosmic Topology . 2023-10-21 . en.
  8. Web site: G. Chelnokov, A. Mednykh . 2020-09-14 . On the coverings of Hantzsche-Wendt manifold . 2023-10-21 . en.
  9. Web site: Sam Tomaino . Analog Science Fiction and Fact – July/August 2023 - Vol. XCIII, Nos. 7 & 8 . 2024-01-24 . en.
  10. Web site: John O'Neill . 2023-07-23 . Wooden Pirates, Group Therapy For Super Heroes And Crab Gods: July-August 2023 Print SF Magazines . 2024-04-19 . en.
  11. Web site: Bickerdike . Mike . 2023-08-02 . Analog, July/August 2023 . 2024-05-15 . tangentonline.com.
  12. Web site: Analytical Laboratory Finalists . 2024-05-14 . analogsf.com.
  13. Web site: 2024-02-23 . 2023 Analog AnLab and Asimov’s Readers’ Awards Finalists . 2024-05-14 . locusmag.com.

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