Simon Ekhammar
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Simon Ekhammar has a total of 8 co-authors. Here are the top co-authors by number of shared publications:
- Dmytro Volin
Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
5 shared publications - Charles Thull
Department of Physics and Astronomy Uppsala University Box 516 SE-751 20 Uppsala Sweden
3 shared publications - Joseph A. Minahan
Uppsala University
3 shared publications - Bengt E. W. Nilsson
Department of Physics Chalmers University of Technology SE-412 96 Göteborg Sweden
2 shared publications - Andrea Cavaglià
INFN sezione di Torino
1 shared publication - Hongfei Shu
Zhengzhou University
1 shared publication
Latest Publications
- Open Access
- 12 February 2025
- Published by Springer Nature in Letters in Mathematical Physics
- Vol. 115 (1) , 1-44
Bethe algebra using pure spinors
We explore a $${\mathfrak {gl}}_{r}$$ -covariant parameterisation of Bethe algebra appearing in $${\mathfrak {so}}_{2r}$$ integrable models, demonstrate its geometric origin from a fused flag, and use it to compute the spectrum of periodic rational spin chains, for various choices of the rank r and Drinfeld polynomials.- 12 February 2025
- Published by Springer Nature in Letters in Mathematical Physics
- Vol. 115 (1) , 1-44
Open AccessBethe algebra using pure spinors
We explore a $${\mathfrak {gl}}_{r}$$ -covariant parameterisation of Bethe algebra appearing in $${\mathfrak {so}}_{2r}$$ integrable models, demonstrate its geometric origin from a fused flag, and use it to compute the spectrum of periodic rational spin chains, for various choices of the rank r and Drinfeld polynomials. - Open Access
- 13 December 2023
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2023 (12) , 1-38
Exploring the Quantum Spectral Curve for AdS3/CFT2
Despite the rich and fruitful history of the integrability approach to string theory on the AdS3× S3× T4background, it has not been possible to extract many concrete predictions from integrability, except in a strict asymptotic regime of large quantum numbers, due to the severity of wrapping effects. The situation changed radically with two independent and identical proposals for the Quantum Spectral Curve (QSC) for this system in a background of pure Ramond-Ramond flux. In other integrable superstring backgrounds there is compelling evidence that this formulation captures all wrapping effects exactly and describes the full planar spectrum. This great success motivates us to study the new proposed QSC and develop methods to extract from it concrete predictions for spectral data. The AdS3× S3× T4case presents a significant novel feature and challenge compared to its higher-dimensional analogues — massless modes. It has been conjectured that these manifest themselves in a new property of this QSC: the non-quadratic nature of the branch-cut singularities of the QSC Q-functions. This feature implies new technical challenges in solving the QSC equations as compared to the well-studied case of $$ \mathcal{N} $$ = 4 SYM. In this paper we resolve these difficulties and obtain the first ever predictions for unprotected string excitations in the planar limit with finite quantum numbers and RR flux. We explain how to extract a systematic expansion around the analogue of the weak ’t Hooft coupling limit in $$ \mathcal{N} $$ = 4 SYM and also obtain high-precision numerical results. These concrete data and others obtainable from the QSC could help to identify the so-far mysterious dual CFT.- 13 December 2023
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2023 (12) , 1-38
Open AccessExploring the Quantum Spectral Curve for AdS3/CFT2
Despite the rich and fruitful history of the integrability approach to string theory on the AdS3× S3× T4background, it has not been possible to extract many concrete predictions from integrability, except in a strict asymptotic regime of large quantum numbers, due to the severity of wrapping effects. The situation changed radically with two independent and identical proposals for the Quantum Spectral Curve (QSC) for this system in a background of pure Ramond-Ramond flux. In other integrable superstring backgrounds there is compelling evidence that this formulation captures all wrapping effects exactly and describes the full planar spectrum. This great success motivates us to study the new proposed QSC and develop methods to extract from it concrete predictions for spectral data. The AdS3× S3× T4case presents a significant novel feature and challenge compared to its higher-dimensional analogues — massless modes. It has been conjectured that these manifest themselves in a new property of this QSC: the non-quadratic nature of the branch-cut singularities of the QSC Q-functions. This feature implies new technical challenges in solving the QSC equations as compared to the well-studied case of $$ \mathcal{N} $$ = 4 SYM. In this paper we resolve these difficulties and obtain the first ever predictions for unprotected string excitations in the planar limit with finite quantum numbers and RR flux. We explain how to extract a systematic expansion around the analogue of the weak ’t Hooft coupling limit in $$ \mathcal{N} $$ = 4 SYM and also obtain high-precision numerical results. These concrete data and others obtainable from the QSC could help to identify the so-far mysterious dual CFT. - Open Access
- 11 October 2023
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2023 (10) , 1-25
The ABJM Hagedorn Temperature from Integrability
A bstract: We use the quantum spectral curve to compute the Hagedorn temperature for ABJM theory in terms of the interpolating function h ( λ ). At weak coupling we compute this temperature up to eight-loop order, showing that it matches the known tree-level and two-loop results. At strong coupling we compute the dependence numerically, showing that it is consistent with expectations from supergravity and the plane-wave limit for the four leading terms in the strong coupling expansion, up to an overall shift of the zero-point energy for type IIA string theory on AdS 4 × ℂP 3 . We conjecture an analytic form for this shift to leading order that is consistent with our numerical results.
- 11 October 2023
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2023 (10) , 1-25
Open AccessThe ABJM Hagedorn Temperature from Integrability
A bstract: We use the quantum spectral curve to compute the Hagedorn temperature for ABJM theory in terms of the interpolating function h ( λ ). At weak coupling we compute this temperature up to eight-loop order, showing that it matches the known tree-level and two-loop results. At strong coupling we compute the dependence numerically, showing that it is consistent with expectations from supergravity and the plane-wave limit for the four leading terms in the strong coupling expansion, up to an overall shift of the zero-point energy for type IIA string theory on AdS 4 × ℂP 3 . We conjecture an analytic form for this shift to leading order that is consistent with our numerical results.
- Open Access
The ABJM Hagedorn Temperature from Integrability
We use the quantum spectral curve to compute the Hagedorn temperature for ABJM theory in terms of the interpolating function $h(λ)$. At weak coupling we compute this temperature up to eight-loop order, showing that it matches the known tree-level and two-loop results. At strong coupling we compute the dependence numerically, showing that it is consistent with expectations from supergravity and the plane-wave limit for the four leading terms in the strong coupling expansion, up to an overall shift of the zero-point energy for type IIA string theory on AdS$_4\times \mathbb{C}\textrm{P}^3$. We conjecture an analytic form for this shift to leading order that is consistent with our numerical results.Open AccessThe ABJM Hagedorn Temperature from Integrability
We use the quantum spectral curve to compute the Hagedorn temperature for ABJM theory in terms of the interpolating function $h(λ)$. At weak coupling we compute this temperature up to eight-loop order, showing that it matches the known tree-level and two-loop results. At strong coupling we compute the dependence numerically, showing that it is consistent with expectations from supergravity and the plane-wave limit for the four leading terms in the strong coupling expansion, up to an overall shift of the zero-point energy for type IIA string theory on AdS$_4\times \mathbb{C}\textrm{P}^3$. We conjecture an analytic form for this shift to leading order that is consistent with our numerical results. - Open AccessThe asymptotic form of the Hagedorn temperature in planar $\mathcal{N}=4$ super Yang-MillsUsing the supergravity dual and the plane-wave limit as a guide, we conjecture the asymptotic large coupling form of the Hagedorn temperature for planar $\mathcal{N}=4$ super Yang-Mills to order $1/\sqrtλ$. This is two orders beyond the presently known behavior. Using the quantum spectral curve procedure of Harmark and Wilhelm, we show that our conjectured form is in excellent agreement with the numerical results.Open AccessThe asymptotic form of the Hagedorn temperature in planar $\mathcal{N}=4$ super Yang-MillsUsing the supergravity dual and the plane-wave limit as a guide, we conjecture the asymptotic large coupling form of the Hagedorn temperature for planar $\mathcal{N}=4$ super Yang-Mills to order $1/\sqrtλ$. This is two orders beyond the presently known behavior. Using the quantum spectral curve procedure of Harmark and Wilhelm, we show that our conjectured form is in excellent agreement with the numerical results.
- Open Access
Bethe Algebra using Pure Spinors
We propose a gl(r)-covariant parameterisation of Bethe algebra appearing in so(2r) integrable models, demonstrate its geometric origin from a fused flag, and use it to compute the spectrum of periodic rational spin chains, for various choices of the rank r and Drinfeld polynomials.
Open AccessBethe Algebra using Pure Spinors
We propose a gl(r)-covariant parameterisation of Bethe algebra appearing in so(2r) integrable models, demonstrate its geometric origin from a fused flag, and use it to compute the spectrum of periodic rational spin chains, for various choices of the rank r and Drinfeld polynomials.
- Top Cited PapersOpen Access
- 28 March 2022
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2022 (3) , 1-60
Monodromy bootstrap for SU(2|2) quantum spectral curves: from Hubbard model to AdS3/CFT2
We propose a procedure to derive quantum spectral curves of AdS/CFT type by requiring that a specially designed analytic continuation around the branch point results in an automorphism of the underlying algebraic structure. In this way we derive four new curves. Two are based on SU(2|2) symmetry, and we show that one of them, under the assumption of square root branch points, describes Hubbard model. Two more are based on SU(2|2) × SU(2|2). In the special subcase of zero central charge, they both reduce to the unique nontrivial curve which furthermore has analytic properties compatible with PSU(1, 1|2) × PSU(1, 1|2) real form. A natural conjecture follows that this is the quantum spectral curve of AdS/CFT integrable system with AdS3 × S3 × T4 background supported by RR-flux. We support the conjecture by verifying its consistency with the massive sector of asymptotic Bethe equations in the large volume regime. For this spectral curve, it is compulsory that branch points are not of the square root type which qualitatively distinguishes it from the previously known cases.
- 28 March 2022
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2022 (3) , 1-60
Top Cited PapersOpen AccessMonodromy bootstrap for SU(2|2) quantum spectral curves: from Hubbard model to AdS3/CFT2
We propose a procedure to derive quantum spectral curves of AdS/CFT type by requiring that a specially designed analytic continuation around the branch point results in an automorphism of the underlying algebraic structure. In this way we derive four new curves. Two are based on SU(2|2) symmetry, and we show that one of them, under the assumption of square root branch points, describes Hubbard model. Two more are based on SU(2|2) × SU(2|2). In the special subcase of zero central charge, they both reduce to the unique nontrivial curve which furthermore has analytic properties compatible with PSU(1, 1|2) × PSU(1, 1|2) real form. A natural conjecture follows that this is the quantum spectral curve of AdS/CFT integrable system with AdS3 × S3 × T4 background supported by RR-flux. We support the conjecture by verifying its consistency with the massive sector of asymptotic Bethe equations in the large volume regime. For this spectral curve, it is compulsory that branch points are not of the square root type which qualitatively distinguishes it from the previously known cases.
- Open Access
- 9 December 2021
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2021 (12) , 1-29
On the squashed seven-sphere operator spectrum
- 9 December 2021
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2021 (12) , 1-29
Open AccessOn the squashed seven-sphere operator spectrum
- Open Access
Monodromy Bootstrap for SU(2|2) Quantum Spectral Curves: From Hubbard model to AdS3/CFT2
We propose a procedure to derive quantum spectral curves of AdS/CFT type by requiring that a specially designed analytic continuation around the branch point results in an automorphism of the underlying algebraic structure. In this way we derive four new curves. Two are based on SU(2|2) symmetry, and we show that one of them, under the assumption of square root branch points, describes Hubbard model. Two more are based on SU(2|2) x SU(2|2). In the special subcase of zero central charge, they both reduce to the unique nontrivial curve which furthermore has analytic properties compatible with PSU(1,1|2) x PSU(1,1|2) real form. A natural conjecture follows that this is the quantum spectral curve of AdS/CFT integrable system with AdS3 x S3 x T4 background supported by RR-flux. We support the conjecture by verifying its consistency with the massive sector of asymptotic Bethe equations in the large volume regime. For this spectral curve, it is compulsory that branch points are not of the square root type which qualitatively distinguishes it from the previously known cases.
Open AccessMonodromy Bootstrap for SU(2|2) Quantum Spectral Curves: From Hubbard model to AdS3/CFT2
We propose a procedure to derive quantum spectral curves of AdS/CFT type by requiring that a specially designed analytic continuation around the branch point results in an automorphism of the underlying algebraic structure. In this way we derive four new curves. Two are based on SU(2|2) symmetry, and we show that one of them, under the assumption of square root branch points, describes Hubbard model. Two more are based on SU(2|2) x SU(2|2). In the special subcase of zero central charge, they both reduce to the unique nontrivial curve which furthermore has analytic properties compatible with PSU(1,1|2) x PSU(1,1|2) real form. A natural conjecture follows that this is the quantum spectral curve of AdS/CFT integrable system with AdS3 x S3 x T4 background supported by RR-flux. We support the conjecture by verifying its consistency with the massive sector of asymptotic Bethe equations in the large volume regime. For this spectral curve, it is compulsory that branch points are not of the square root type which qualitatively distinguishes it from the previously known cases.
- Open Access
On the squashed seven-sphere operator spectrum
We derive major parts of the eigenvalue spectrum of the operators on the squashed seven-sphere that appear in the compactification of eleven-dimensional supergravity. These spectra determine the mass spectrum of the fields in $AdS_4$ and are important for the corresponding ${\mathcal N} =1$ supermultiplet structure. This work is a continuation of the work in [1] where the complete spectrum of irreducible isometry representations of the fields in $AdS_4$ was derived for this compactification. Some comments are also made concerning the $G_2$ holonomy and its implications on the structure of the operator equations on the squashed seven-sphere.Open AccessOn the squashed seven-sphere operator spectrum
We derive major parts of the eigenvalue spectrum of the operators on the squashed seven-sphere that appear in the compactification of eleven-dimensional supergravity. These spectra determine the mass spectrum of the fields in $AdS_4$ and are important for the corresponding ${\mathcal N} =1$ supermultiplet structure. This work is a continuation of the work in [1] where the complete spectrum of irreducible isometry representations of the fields in $AdS_4$ was derived for this compactification. Some comments are also made concerning the $G_2$ holonomy and its implications on the structure of the operator equations on the squashed seven-sphere.