Award Abstract # 1905717
Extensions of Modern Homological Invariants in Low Dimensional Topology

NSF Org: DMS
Division Of Mathematical Sciences
Recipient: UNIVERSITY OF CALIFORNIA, LOS ANGELES
Initial Amendment Date: May 23, 2019
Latest Amendment Date: May 26, 2022
Award Number: 1905717
Award Instrument: Continuing Grant
Program Manager: Swatee Naik
snaik@nsf.gov
 (703)292-4876
DMS
 Division Of Mathematical Sciences
MPS
 Directorate for Mathematical and Physical Sciences
Start Date: September 1, 2019
End Date: August 31, 2024 (Estimated)
Total Intended Award Amount: $319,581.00
Total Awarded Amount to Date: $319,581.00
Funds Obligated to Date: FY 2019 = $190,709.00
FY 2020 = $64,436.00

FY 2021 = $64,436.00
History of Investigator:
  • Sucharit Sarkar (Principal Investigator)
    sucharit@math.ucla.edu
Recipient Sponsored Research Office: University of California-Los Angeles
10889 WILSHIRE BLVD STE 700
LOS ANGELES
CA  US  90024-4200
(310)794-0102
Sponsor Congressional District: 36
Primary Place of Performance: University of California-Los Angeles
Los Angeles
CA  US  90095-1555
Primary Place of Performance
Congressional District:
36
Unique Entity Identifier (UEI): RN64EPNH8JC6
Parent UEI:
NSF Program(s): TOPOLOGY
Primary Program Source: 01001920DB NSF RESEARCH & RELATED ACTIVIT
01002021DB NSF RESEARCH & RELATED ACTIVIT

01002122DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):
Program Element Code(s): 126700
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.049

ABSTRACT

Topology is the branch of mathematics that studies shapes of spaces. Topology has several real-world applications, such as studying DNA knotting, constructing new data encryption algorithms, analyzing large data sets, motion planning for robotics, and developing quantum field theories in physics, to name a few. Due to a famous theorem by Smale, topology in higher dimensions is somewhat simpler than topology in lower dimensions. Therefore, it is interesting to concentrate only on spaces up to dimension four; this sub-field is called low-dimensional topology. These low-dimensions also correspond to the spaces that we live in---we live in a three-dimensional space, and if one includes time, in a four-dimensional spacetime---making low-dimensional topology even more pertinent. In low-dimensional topology, we are specifically interested in knot theory, where one studies one-dimensional objects inside three-dimensional spaces, such as knotted pieces of strings. Knot theory is a fundamentally important topic in low-dimensional topology, and it is also an integral part of many of the real-world topological applications. Knot theory studies whether a knot can be transformed into another without tearing or crossing itself (such a transformation is called an isotopy), and if not, what sort of modifications need to be made to ensure they become isotopic. Knot invariants are mathematical objects (such as numbers or groups) associated to knots which remain unchanged during such an isotopy, and consequently, are extensively used in studying knots. The current project is focused on knot theory and will explore existing knot invariants and construct new ones.

This project will concentrate on two modern families of knot invariants in low-dimensional topology, knot Floer homology and Khovanov homology, which have been employed for a variety of applications ever since their discovery at the turn of the millennium. The main aim of the project is to construct new extensions, such as spatial refinements, of various versions of these existing invariants. Specifically, the project has the following four goals: construct further spatial refinements of Khovanov homology invariants and their perturbations; construct a spatial refinement of knot Floer homology using grid presentations; study group actions on Lagrangian Floer homology; and construct new combinatorial spectral sequences from Khovanov homology. Additionally, several activities combining research with educational and other broader impacts will be organized as part of this project, such as increasing mathematical awareness and interest among children at Los Angeles Math Circle.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

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Cheng, Zhechi and Hedden, Matthew and Sarkar, Sucharit "Murasugi sum and extremal knot Floer homology" Quantum Topology , 2024 https://doi.org/10.4171/qt/186 Citation Details
Lawson, Tyler and Lipshitz, Robert and Sarkar, Sucharit "Homotopy functoriality for Khovanov spectra" Journal of Topology , v.15 , 2022 https://doi.org/10.1112/topo.12274 Citation Details
Lipshitz, Robert and Sarkar, Sucharit "A mixed invariant of nonorientable surfaces in equivariant Khovanov homology" Transactions of the American Mathematical Society , v.375 , 2022 https://doi.org/10.1090/tran/8736 Citation Details
Lipshitz, Robert and Sarkar, Sucharit "Khovanov homology detects split links" American Journal of Mathematics , v.144 , 2022 https://doi.org/10.1353/ajm.2022.0043 Citation Details

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

This project was about knot theory, which studies knots and links, which are knotted 1-dimensional objects (like circles) in the 3-dimensional space.  One also studies time-evolution of these knots, called cobordisms, which can be viewed as knotted 2-dimensional objects (like surfaces) in a 4-dimensional space (with time being the additional dimension.) Knots are usually studied via invariants, which remain unchanged under deformation of the 1-dimensional objects. Two modern knot invariants are Khovanov homology and knot Floer homology, which were the main objects of study in this project. Several new applications of these invariants were discovered in this project by the PI and his collaborators, which are listed below.

1. Khovanov homology can be used to completely detect if two knotted circles can be separated. 

2. If there is additional rotational symmetry of the knot, then there is a relation between the Khovanov homology of the original knot and the Khovanov homology of its quotient knot. (An example of a knot with a 180-degree rotational symmetry and its quotient knot are shown in the accompanying image.)

3. If there is a cobordism from one knot to another, then there is a way to map the Khovanov space of the first knot into the Khovanov space of the second.

4. If there is a non-orientable (one-sided, like a Mobius strip) cobordism from one knot to another, then there is a brand new invariant of this cobordism defined by mixing two versions of Khovanov homology.

5. If two knots are joined together to form a new knot by a process called Murasugi sum, then the top term of the knot Floer homology of the new knot can be computed in terms of the top terms of the knot Floer homology of the constituent knots.

6. There is a stronger knot invariant than knot Floer homology, which is a knot Floer space, whose homology is knot Floer homology.


Last Modified: 12/19/2024
Modified by: Sucharit Sarkar

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