Talk:Multiple time dimensions

message: I've created this page after discovering a lot of material on extra time dimensions on the F-theory page, some of which is wrong and most of which is distracting. That material was moved there from the now deleted page "Second Temporal Dimension" (revision history, discussion), after Wikipedia's resident string theorist said it was appropriate to have a page on two-time theories. I am not going to restore that content here, not right away anyway, but you can see it all here. Mporter (talk) 07:13, 23 December 2007 (UTC)
thread_title:  Rationale for this page 

message: I have added a link to Imaginary time and I wonder if that equally short article should be merged in here? — Cheers, Steelpillow (Talk) 13:57, 22 December 2016 (UTC)
thread_title:  Imaginary time 

message: I added... Time is One-Dimension, however it has 12 Aspects. 7 regular time: beginning, end, past, present, future, void, a constant (speed-of-light). 4 hypertime: fast-forward, reverse, stop/pause, before the beginning/after the end. Imaginary time is the 12th aspect. 2601:580:100:5D52:84C4:1F50:7E5B:17FB (talk) 16:23, 1 October 2018 (UTC)
replies: text: Not relevant to multiple dimensions, and not reliably sourced. I see somebody else has already removed it. — Cheers, Steelpillow (Talk) 17:59, 1 October 2018 (UTC)
thread_title:  12 Aspects of 1-Dimensional Time 

message: I recommend extending the last paragraph of the  Physics section of the article:
:: Theories with more than one dimension of time have sometimes been advanced in physics, whether as a serious description of reality or just as a curious possibility. Itzhak Bars's work on "two-time physics",[2] inspired by the SO(10,2) symmetry of the extended supersymmetry structure of M-theory, is the most recent and systematic development of the concept (see also F-theory). Walter Craig and Steven Weinstein proved the existence of a well-posed initial value problem for the ultrahyperbolic equation (a wave equation in more than one time dimension).[3] This showed that initial data on a mixed (spacelike and timelike) hypersurface obeying a particular nonlocal constraint evolves deterministically in the remaining time dimension. 
Into a a new (second-level) section "(1.2) Higher Time-Dimension Theories":
:: There are alternative theories involving higher time dimensions. These represent a blend of serious descriptions of reality, mathematical possibilities, or curious philosophical ideas. 
::: 1.2.1 Itzhak Bars's work on "two-time physics",[2] inspired by the SO(10,2) symmetry of the extended supersymmetry structure of M-theory, is the most recent and systematic development of the concept (see also F-theory). 
::: 1.2.2 Walter Craig and Steven Weinstein proved the existence of a well-posed initial value problem for the ultrahyperbolic equation (a wave equation in more than one time dimension).[3] This showed that initial data on a mixed (spacelike and timelike) hypersurface obeying a particular nonlocal constraint evolves deterministically in the remaining time dimension. 
::: 1.2.3 The five-dimensional space-time-matter consortium developed the 5DSTM theory. Paul Wesson and his colleagues Principles of Space-Time-Matter: Cosmology, Particles and Waves in Five Dimensions (coauthor James Overduin), 2018, World Scientific, Singapore extended the Kaluza–Klein theory, to account for matter along with time and space. They discovered that while the universe may have a big-bang singularity in 4D, it is smooth in 5D space.
::: 1.2.4 Complex-time (kime) and space-kime is another generalization of Kaluza–Klein theory, which lifts the time from positive reals into the complex plain. The major advantage of this approach is that it enables space-kime inference and data-driven analytics based on the extension of longitudinal data (e.g., time-series) to kime-surfaces over the 5D space-kime manifold, which is complete and solves many of the problems of time http://www.spacekime.org.
:::: 99.19.71.139 (talk) 23:11, 4 January 2020 (UTC)
replies: text: Done. Hope I got it about right. — Cheers, Steelpillow (Talk) 11:10, 5 January 2020 (UTC)
thread_title:  Suggest an extension of "Physics" section

message: This section concludes:
:"...the existence of the Planck length and the constancy of the speed of light can be derived.[citation needed]
:"As a consequence of this model it has been suggested that the speed of light may not have been constant in the early universe.[ref]"
On the face of it these two statements are contradictory. The cited source discusses some consequences of a variable speed of light but deliberately avoids any mechanism (such as this model, supposedly) to achieve that. Is there genuinely something to say here or is this whole section a hoax? — Cheers, Steelpillow (Talk) 11:03, 20 June 2020 (UTC)
thread_title:  Planck length and speed of light 

message: Due to the major cultural impact of The Lord of the Rings and the Chronicles of Narnia, I have added a section on (multiple time dimensions in) literary fiction. DISCLAIMER: I am the author of the study cited for CS Lewis and Narnia, and have made the addition after due consideration of WP:EXPERT. — Cheers, Steelpillow (Talk) 13:02, 20 June 2020 (UTC)
replies: text: I'd suggest the short story "Star, Bright" as an additional, more exotic literary example; a couple of incredibly gifted kids discover a mental trick to first teleport, then time travel, then discover that time is a closed loop since those in the far future escaped a catastrophe by going into the distant past. The kids disappeared...and the girl's father, less gifted but smart enough to guess what they may have done, also disappears, trying to follow them using a higher dimensional version of the mental trick, to whatever was off the closed loop. Rlhamil (talk) 19:46, 24 March 2024 (UTC)
replies: text: You would need to cite an independent literary source verifying the literary significance of the tale: these articles are not fan lists. — Cheers, Steelpillow (Talk) 19:57, 24 March 2024 (UTC)
thread_title:  Literary fiction 

message: It may be appropriate to include a new section "Mathematics and Statistics", just below "Physics", and above "Philosophy",  that covers two relevant developments regarding multidimensional time, e.g., complex time (kime). 
Specifically, in mathematics and the study of partial differential equations (PDEs), higher dimensional time formulations lead to Ultrahyperbolic equations. In general, such ultrahyperbolic equations in two or more time dimensions are ill-posed, don't permit stable, global, and consistent solutions Courant, R. and Hilbert, D., 2008. Methods of mathematical physics: partial differential equations. John Wiley & Sons.
However, under certain non-local constraints, ultrahyperbolic equations can have stable, consistent, and global solutions, which offers a unique mathematical-physics perspective on modeling temporal dynamics and longitudinal processes Craig Walter and Weinstein Steven. (2009) On determinism and well-posedness in multiple time dimensionsProc. R. Soc. A.4653023–3046, http://doi.org/10.1098/rspa.2009.0097, Dinov, ID and Velev, MV. (2021) Data Science: Time Complexity, Inferential Uncertainty, and Spacekime Analytics, De Gruyter, STEM Series, ISBN 978-3-11-069780-3, DOI 10.1515/9783110697827.
In statistics, data science, and artificial intelligence, the lifting time from the positive reals to the complex plane, and higher dimensions, offers unique mechanisms of transforming flat curvy-linear time-courses (e.g., time-series) as multidimensional manifolds (kime-surfaces). This generalization of multidimensional time leads to enriched representations of observations where random (independent and identically distributed) samples can be framed into a Bayesian framework, defined over manifold structures, and analyzed using advanced artificial intelligence methods Zhang, R, Zhang, Y, Liu, Y, Guo, Y, Shen, Y, Deng, D, Qiu, Y, Dinov, ID. (2022) Kimesurface Representation and Tensor Linear Modeling of Longitudinal Data, Neural Computing and Applications Journal, 34:6377–6396, DOI: 10.1007/s00521-021-06789-8., Wang, Y, Shen Y, Deng, D, Dinov, ID. (2022) Determinism, Well-posedness, and Applications of the Ultrahyperbolic Wave Equation in Spacekime, Journal of Partial Differential Equations in Applied Mathematics, 5(100280), DOI: 10.1016/j.padiff.2022.100280 .  99.19.71.139 (talk) 20:58, 4 July 2022 (UTC)
replies: text: I think we need some secondary or tertiary sources to clarify what is going on here and to demonstrate that this weird "kime" jargon has some acceptance from the mainstream. For example in the concert hall discussion in one source, audio engineers are already well familiar with the complex-number phasing of audio signals in time, so it needs such sources to explain how and why this "kime" model is different and also how it adds practical value over and above the conventional picture. — Cheers, Steelpillow (Talk) 17:08, 5 July 2022 (UTC)
replies: text: There seems to be a fundamental difference between the classical Fourier transform of signals (in the Steelpillow's example above, audio sounds), which transforms the information into k-space (Fourier domain), and the complex-time (kime) representation of data. The latter is more general than a single audio signal. In the above sound-engineer example, the kime representation is more like a set of repeated IID samples of the same melody. In essence, the kime representation is still in the "spatiotemporal" domain, not the Fourier domain. Of course, the kime representation of the data can still be transformed into the k-space, just like a single audio signal can. The main difference is that the data over complex time (a kime-surface) represents a complete IID sample (e.g., a set of individual time-series), not just one observation (e.g., a single audio). The mathematics of complex time is intricate, as it requires special care to ensure existence, stability, and domain scope of PDE solutions. Similarly, the Bayesian statistical formulation of the complex time representation of data provide an alternative way to look at independent and identically distributed samples, and hence, the inference on the underlying distribution processes. 99.19.71.139 (talk) 01:30, 10 July 2022 (UTC)
thread_title:  Mathematics and Statistics