<p>We report on a search for axion dark matter in the frequency range near 5.9 GHz, conducted using the haloscope technique. The experiment employed an 8-cell microwave resonator designed to extend the accessible frequency range by a multifold factor relative to conventional single-cell configurations, while maintaining a large detection volume. To enhance sensitivity, a flux-driven Josephson parametric amplifier operating near the quantum noise limit was utilized, together with a sideband-summing method that coherently combines mirrored spectral components generated by the Josephson parametric amplifier. Data were acquired over the frequency range 5.83–5.94 GHz. With no statistically significant excess observed, we exclude axion-photon couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>g</mi></mrow><mrow><mi>a</mi><mi>γ</mi><mi>γ</mi></mrow></msub></mrow></math> down to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1.2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>14</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mrow><msup><mrow><mi>GeV</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></mrow></math> at a 90% confidence level. The achieved sensitivity approaches the Kim-Shifman-Vainshtein-Zakharov benchmark prediction, setting the most stringent limits to date in this range.</p>

South Korea

Saebyeok Ahn

Çağlar Kutlu

Soohyung Lee

SungWoo Youn

Sergey V. Uchaikin

Sungjae Bae

Sweden

Junu Jeong

Japan

Arjan F. van Loo

Yasunobu Nakamura

Seongjeong Oh

Jihn E. Kim

Yannis K. Semertzidis

Probing Kim-Shifman-Vainshtein-Zakharov Axion Dark Matter near 5.9 GHz Using an 8-Cell Cavity Haloscope

<p>Axions, originally proposed to resolve the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math> problem in the strong interaction, remain a leading dark matter candidate. While cavity haloscopes offer the most sensitive technique for detecting axions, searches have largely been limited to masses below <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>μeV</mi></mrow></math>. We report a sensitive search for axion dark matter with masses around <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>21</mn><mtext> </mtext><mtext> </mtext><mi>μeV</mi></mrow></math>, utilizing the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>TM</mi></mrow><mrow><mn>020</mn></mrow></msub></mrow></math> mode of a cylindrical cavity equipped with an innovative tuning mechanism. Our search achieved a sensitivity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1.7</mn><mo>×</mo></math> the Kim-Shifman-Vainshtein-Zakharov benchmark over a 100-MHz range, representing a significant advance in this mass range. These results demonstrate that higher-order modes provide a viable strategy for extending haloscope searches into previously unexplored higher-mass regions.</p>

Germany

Younggeun Kim

Jinsu Kim

Seonjeong Oh

Taehyeon Seong

Sergey Uchaikin

Axion Dark Matter Search with Sensitivity near the Kim-Shifman-Vainshtein-Zakharov Benchmark Using the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>TM</mi></mrow><mrow><mn>020</mn></mrow></msub></mrow></math> Mode

It has been known for some time that the cosmological bound on the invisible axion scale can be avoided by an early phase of strong QCD. While most approaches rely on theories where the strong coupling constant is determined through the expectation value of some scalar field, we show that this mechanism can also be implemented into the benchmark Kim-Shifman-Vainshtein-Zakharov and Dine-Fischler-Srednicki-Zhitnitsky models when the early phase of strong QCD emerges by the modification of the running coupling during inflation. For both models the physics that are responsible for making QCD strong do not displace the axions minimum by too much, so that the efficiency of the relaxation is controlled by parameters of the theory and the number of inflationary <math><mi>e</mi></math>-folds. In particular, we consider the case of very efficient relaxation where the axion abundance is dominated by inflationary quantum and postinflationary thermal fluctuations. Within this situation we identify the parameter space compatible with all cosmological constrains and derive conditions on the reheating temperature and the QCD scale during inflation that result in the axion making up all the dark matter. Because of duality below the Peccei-Quinn scale and a minor influence of the Kim-Shifman-Vainshtein-Zakharov and Dine-Fischler-Srednicki-Zhitnitsky fields on the running, our findings also apply to a minimal two-form implementation of the axion.

Emmanouil Koutsangelas

Removing the cosmological bound on the axion scale in the Kim-Shifman-Vainshtein-Zakharov and Dine-Fischler-Srednicki-Zhitnitsky models

We study the index of 4d <math><mi>N</mi><mo>=</mo><mn>4</mn></math> Yang-Mills theory with <math><mi>U</mi><mo>(</mo><mi>N</mi><mo>)</mo></math> gauge group, focusing on the physics of the dual Bogomolny-Prasad-Sommerfield black holes in <math><msub><mi>AdS</mi><mn>5</mn></msub><mo>×</mo><msup><mi>S</mi><mn>5</mn></msup></math>. Certain aspects of these black holes can be studied from finite <math><mi>N</mi></math> indices with reasonably large <math><msup><mi>N</mi><mn>2</mn></msup></math>. We make numerical studies of the index for <math><mi>N</mi><mo>≤</mo><mn>6</mn></math>, by expanding it up to reasonably high orders in the fugacity. The entropy of the index agrees very well with the Bekenstein-Hawking entropy of the dual black holes, say at <math><msup><mi>N</mi><mn>2</mn></msup><mo>=</mo><mn>25</mn></math> or 36. Our data clarifies and supports the recent ideas which allowed analytic studies of these black holes from the index, such as the complex saddle points of the Legendre transformation and the oscillating signs in the index. In particular, the complex saddle points naturally explain the <math><mfrac><mn>1</mn><mi>N</mi></mfrac></math>-subleading oscillating patterns of the index. We also illustrate the universality of our ideas by studying a model given by the inverse of the MacMahon function.

United Kingdom

Prarit Agarwal

Sunjin Choi

United States

Joonho Kim

Seok Kim

June Nahmgoong

AdS black holes and finite <math><mi>N</mi></math> indices

We explore 6d (1, 0) superconformal field theories with SU(3) and SU(2) gauge symmetries which cascade after Higgsing to the E-string theory on a single M5 near an E 8 wall. Specifically, we study the 2d   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = (0, 4) gauge theories which describe self-dual strings of these 6d theories. The self-dual strings can be also viewed as instanton string solitons of 6d Yang-Mills theories. We find the 2d anomaly-free gauge theories for self-dual strings, amending the naive ADHM gauge theories which are anomalous, and calculate their elliptic genera. While these 2d theories respect the flavor symmetry of each 6d SCFT only partially, their elliptic genera manifest the symmetry fully as these functions as BPS index are invariant in strongly coupled IR limit. Our consistent 2d (0, 4) gauge theories also provide new insights on the non-linear sigma models for the instanton strings, providing novel UV completions of the small instanton singularities. Finally, we construct new 2d quiver gauge theories for the self-dual strings in 6d E-string theory for multiple M5-branes probing the E 8 wall, and find their fully refined elliptic genera.

Kimyeong Lee

Higgsing towards E-strings

We propose new ADHM-like methods to compute the Coulomb branch instanton partition functions of 5D and 6D supersymmetric gauge theories, with certain exceptional gauge groups or exceptional matters. We study <math><msub><mi>G</mi><mn>2</mn></msub></math> theories with <math><msub><mi>n</mi><mn>7</mn></msub><mo>≤</mo><mn>3</mn></math> matters in <math><mrow><mn>7</mn></mrow></math> and <math><mi>S</mi><mi>O</mi><mo>(</mo><mn>7</mn><mo>)</mo></math> theories with <math><msub><mi>n</mi><mn>8</mn></msub><mo>≤</mo><mn>4</mn></math> matters in the spinor representation <math><mrow><mn>8</mn></mrow></math>. We also study the elliptic genera of self-dual instanton strings of 6D SCFTs with exceptional gauge groups or matters, including all non-Higgsable atomic SCFTs with rank 2 or 3 tensor branches. Some of them are tested with topological vertex calculus. We also explore a D-brane-based method to study instanton particles of 5D <math><mi>S</mi><mi>O</mi><mo>(</mo><mn>7</mn><mo>)</mo></math> and <math><mi>S</mi><mi>O</mi><mo>(</mo><mn>8</mn><mo>)</mo></math> gauge theories with matters in spinor representations, which further tests our ADHM-like proposals.

Hee-Cheol Kim

Ki-Hong Lee

Jaemo Park

6D strings and exceptional instantons

We study the asymptotic behavior of the (modified) superconformal index for 4d   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 1 gauge theory. By considering complexified chemical potential, we find that the ‘high-temperature limit’ of the index can be written in terms of the conformal anomalies 3c − 2a. We also find macroscopic entropy from our asymptotic free energy when the Hofman-Maldacena bound 1/2 &lt; a/c &lt; 3/2 for the interacting SCFT is satisfied. We study   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 1 theories that are dual to AdS5 × Y  p,p  and find that the Cardy limit of our index accounts for the Bekenstein-Hawking entropy of large black holes.

Jaewon Song

A 4d   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 1 Cardy Formula

Corrected the authors’ affiliations. Affiliation a and c were swapped.

China

Sung-Soo Kim

Erratum to: Instantons from blow-up

We generalize Nakajima-Yoshioka blowup equations to arbitrary gauge group with hypermultiplets in arbitrary representations. Using our blowup equations, we compute the instanton partition functions for 4d $$ \mathcal{N} $$ = 2 and 5d $$ \mathcal{N} $$ = 1 gauge theories for arbitrary gauge theory with a large class of matter representations, without knowing explicit construction of the instanton moduli space. Our examples include exceptional gauge theories with fundamentals, SO( ) gauge theories with spinors, and SU(6) gauge theories with rank-3 antisymmetric hypers. Remarkably, the instanton partition function is completely determined by the perturbative part.

Instantons from blow-up

We study the elliptic genera of 6d strings based on their modular properties. They are weak Jacobi forms of weight 0, whose indices are determined from the 2d chiral anomalies. We propose the ansatz for the elliptic genera which reflects the analytic structure of instanton partition functions. Given a finite amount of initial BPS data, we completely determine the elliptic genera of 6d strings in various 6d SCFTs. We also apply our ansatz to study   <math> <mi>N</mi> <mo>=</mo> <mfenced> <mn>2</mn> <mn>0</mn> </mfenced> </math>  $$ \mathcal{N}=\left(2,0\right) $$  and (1, 1) little strings as well as   <math> <mi>N</mi> <mo>=</mo> <mfenced> <mn>1</mn> <mn>0</mn> </mfenced> </math>  $$ \mathcal{N}=\left(1,0\right) $$  heterotic little strings, for which T-duality of little string theories supplies a sufficient number of initial BPS data. The anomaly polynomials of 6d little strings are worked out, which is needed for the elliptic genera bootstrap. In some little string theories, the elliptic genera must have the extra contributions from the Coulomb branch, which correspond to the additional zero modes for the full strings. The modified ansatze for such elliptic genera are also discussed.

On elliptic genera of 6d string theories