The cross sections of the ( <italic>&#945;, &#947;</italic>) reactions on the lightest <italic>p</italic>-nucleus, 74Se, and on 76Se were measured using the 4 <italic>&#960; &#947;</italic>-summing method and isotopically enriched targets at center-of-mass energies between 5.950 and 8.417 MeV, within the relevant Gamow window for <italic>p</italic>-process nucleosynthesis. The experimental cross-section data were compared with statistical-model calculations performed using the most recent version (2.2) of the nuclear reaction code TALYS, with the aim of constraining existing global models of the <italic>&#945;</italic>-particle&#8211;nucleus Optical Model Potential ( <italic>&#945;</italic>-OMP) and assessing the performance of two newly developed semi-microscopic models, one for the nuclear level density (NLD) and one for the photon strength function (PSF). Overall, very good agreement between the TALYS-2.2 calculations and the experimental data was found. Using a standard <italic>&#967;</italic> 2 analysis and a goodness-of-fit estimator ( <italic>F<inf>rms</inf></italic>), the model combination of the nucleon&#8211;nucleus Optical Model Potential ( <italic>p</italic>/ <italic>n</italic>-OMP), <italic>&#945;</italic>-OMP, NLD, and PSF that successfully reproduces the experimental cross sections was identified for each investigated reaction. Finally, the reaction rates obtained from the best model combinations were compared with those provided by well-established reaction-rate databases.

S. Harissopulos

Greece

V. Foteinou

M. Axiotis

Germany

F. Maragkos

H.W. Becker

A. Lagoyannis

Austria

P. Dimitriou

( <italic>&#945;, &#947;</italic>) Cross-section measurements on the lightest <italic>p</italic> nucleus 74Se and on 76Se

In this paper we test Non-Conservative Conformal Killing Gravity (NC-CKG), a geometric extension of general relativity in which the cosmological constant arises as a constant of integration and the energy-momentum tensor is allowed to deviate from covariant conservation through an effective coupling parameter, <italic>&#964;</italic>. We constrain the model with a Bayesian MCMC analysis combining Cosmic Chronometers, DESI DR2 baryon acoustic oscillations, and three Type Ia supernova compilations (Pantheon+, Union3, and DES-Dovekie). Across all dataset combinations, <italic>&#964;</italic> remains consistent with zero, with only a mild tendency toward negative values. A negative <italic>&#964;</italic> corresponds to a faster dilution of the pressureless matter density than the standard <math altimg='si19.svg'><msup><mi>a</mi><mrow><mo>&#8722;</mo><mn>3</mn></mrow></msup></math> scaling, while the current data do not provide statistically significant evidence for a departure from matter conservation. The conformal-Killing density parameter &#937; <inf><italic>D</italic></inf> is negative in all dataset combinations, while the resulting expansion history gives transition redshifts in the range <italic>z<inf>t</inf></italic>&#8239;&#8776;&#8239;0.68&#8211;0.74. When the SH0ES local distance-ladder calibration is included, the model gives <math altimg='si20.svg'><mrow><msub><mi>H</mi><mn>0</mn></msub><mo linebreak='goodbreak'>=</mo><mn>72.85</mn><mo>&#177;</mo><mn>0.98</mn><mspace width='0.33em' /><mrow><mi mathvariant='normal'>km</mi><mspace width='0.16em' /><msup><mi mathvariant='normal'>s</mi><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup><mspace width='0.16em' /><msup><mtext>Mpc</mtext><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></mrow></mrow></math>. This high value is not driven by the additional freedom in <italic>&#964;</italic>, since flat &#923;CDM and conservative CKG give comparable constraints under the same calibration. Model selection via AIC and BIC generally favours the conservative limit ( <math altimg='si21.svg'><mrow><mi>&#964;</mi><mo linebreak='goodbreak'>=</mo><mn>0</mn></mrow></math>) or &#923;CDM over the full non-conservative model. Overall, NC-CKG remains a geometrically motivated alternative to dark energy, although current background-expansion data do not require non-conservation. Future observations will provide stronger tests of the model.

India

M.M. Praveena

Devaraja Mallesha Naik

Testing non-conservative Conformal Killing Gravity with cosmological observations

In this paper, we investigate the production of gravitational waves during the preheating era. To achieve this purpose, we consider Gauss-Bonnet inflation model with Power–law potential, <math altimg='si11.svg'><mrow><mi>V</mi><mrow><mo>(</mo><mi>&#981;</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><msub><mi>V</mi><mn>0</mn></msub><msup><mi>&#981;</mi><mi>n</mi></msup></mrow></math>, and monomial Gauss-Bonnet coupling function, <math altimg='si12.svg'><mrow><mi>&#958;</mi><mrow><mo>(</mo><mi>&#981;</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><msub><mi>&#958;</mi><mn>0</mn></msub><msup><mi>&#981;</mi><mi>n</mi></msup></mrow></math>. We examine our model by comparing our findings with the current observational data. After that, we study the preheating stage by adopting an approach in which we establish a link between preheating duration, reheating phase and inflationary parameters. This step allows us to benefit from observational constraints imposed on inflation. Furthermore, we examine the production of gravitational waves during preheating epoch connecting the energy density to the preheating duration, <italic>N<inf>pre</inf></italic>, and then with the spectral index <italic>n<inf>s</inf></italic>. The generation of gravitational waves during preheating can satisfy observational constraints. In particular, the predicted present-day gravitational-wave energy density, expressed as a function of the scalar spectral index, is consistent with the Planck constraints for the choice of a dimensionless Gauss-Bonnet coupling parameter <math altimg='si13.svg'><mrow><mi>&#945;</mi><mo>&#8801;</mo><mn>4</mn><msub><mi>V</mi><mn>0</mn></msub><msub><mi>&#958;</mi><mn>0</mn></msub><mo linebreak='goodbreak'>/</mo><mn>3</mn><mo linebreak='goodbreak'>=</mo><mo>&#8722;</mo><mn>1.5</mn><mo linebreak='goodbreak'>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>6</mn></mrow></msup></mrow></math>, an effective equation of state parameter <math altimg='si10.svg'><mrow><mi>&#969;</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn><mo linebreak='goodbreak'>/</mo><mn>6</mn></mrow></math>, and a preheating efficiency parameter <math altimg='si14.svg'><mrow><mi>&#948;</mi><mo linebreak='goodbreak'>=</mo><msup><mn>10</mn><mn>5</mn></msup></mrow></math>.

Morocco

Brahim Asfour

Yahya Ladghami

Taoufik Ouali

Gravitational waves production during preheating within GB gravity with monomial coupling

The low-lying level structure of 80Se was investigated via the 76Ge( 9Be, 2p3n) reaction at <italic>E</italic> <inf>lab</inf>&#8239;&#8776;&#8239;31 MeV using a Compton-suppressed HPGe clover array, and level lifetimes were measured with the Doppler-shift attenuation method. Measured excitation energies and <italic>B</italic>( <italic>E</italic>2) transition strengths are reasonably well reproduced by Interacting Boson Approximation (IBA) calculations. The observed excitation-energy and transition-strength patterns associated with the <math altimg='si68.svg'><mrow><mi>&#963;</mi><mo linebreak='goodbreak'>=</mo><mn>5</mn></mrow></math> and <math altimg='si69.svg'><mrow><mi>&#963;</mi><mo linebreak='goodbreak'>=</mo><mn>3</mn></mrow></math> representations, together with candidate members of the <math altimg='si70.svg'><mrow><mi>&#963;</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn></mrow></math> representation, exhibit pronounced O(6)-like collective behavior in this five-boson system. The combined experimental observables and finite-boson IBA calculations indicate a surprisingly good correspondence with O(6) expectations for these selected collective structures. At the same time, the presence of low-lying <math altimg='si71.svg'><msubsup><mn>0</mn><mn>2</mn><mo>+</mo></msubsup></math> and <math altimg='si72.svg'><msubsup><mn>2</mn><mn>3</mn><mo>+</mo></msubsup></math> states that are not consistently accommodated within the same classification, together with a finite <italic>B</italic>( <italic>E</italic>2; <math altimg='si73.svg'><mrow><msubsup><mn>0</mn><mn>3</mn><mo>+</mo></msubsup><mo>&#8594;</mo><msubsup><mn>2</mn><mn>1</mn><mo>+</mo></msubsup><mrow><mo>)</mo></mrow></mrow></math> strength, demonstrates that the O(6) limit does not provide a complete description of the low-energy spectrum. We therefore interpret the present results as evidence for pronounced O(6)-like collective structures embedded within a more complex nuclear structure of 80Se.

R. Biswas

S. Rajbanshi

Habibur Rahaman

Saikat Sen

G. Manna

R. Palit

Abhijit Bisoi

S. Sounda

Sajad Ali

F.S. Babra

R. Banik

Israel

S. Bhattacharya

S. Bhattacharyya

Poland

P. Dey

Md. S.R. Laskar

G. Mukherjee

S. Nandi

Apurba Kumar Nayek

Romania

H. Pai

Rajkumar Santra

T. Trivedi

Emergence of O(6)-like collective structures in 80Se

The growing evidence for nanohertz gravitational waves, from NANOGrav and other observations, may be pointing to a cosmological first-order phase transition at temperatures of <math altimg='si5.svg'><mrow><mi mathvariant='script'>O</mi><mrow><mo>(</mo><mn>10</mn><mo linebreak='badbreak'>&#8722;</mo><mn>100</mn><mo>)</mo></mrow><mspace width='0.28em' /><mtext>MeV</mtext></mrow></math>. Such an interpretation requires beyond the Standard Model dynamics in this energy range. If so, it may well be the case that galactic core-collapse supernova explosions would produce the key components related to the first-order phase transition, leaving detectable imprints on the spectrum of neutrinos emitted in the initial few seconds of the collapse. This might provide further evidence in support of the early universe interpretation of the nanohertz gravitational wave signal. The scenario proposed here is also suggestive of a low-mass seesaw mechanism to explain neutrino masses. We outline the prospects for future observations of Galactic supernovae to uncover the signals of this scenario, with further confirmation from future pulsar timing array measurements of primordial nanohertz gravitational waves.

United States

Hooman Davoudiasl

Peter B. Denton

Anna M. Suliga

Cosmic overture echoed in a stellar final act: Implications of nanohertz gravitational waves for core collapse supernova neutrinos

While universal exponents for phase transitions are well-established at the critical point, the zero-temperature limit remains largely unexplored. The phase transition between small and large black holes in AdS space, analogous to that of a van der Waals fluid, provides an ideal approach for studying the first-order phase transitions near zero temperature, a regime where semi-classical black hole thermodynamics remains exact and can provide a benchmark for quantum gravity. By applying the Maxwell equal-area law to the coexistence curve, we analytically derive a set of universal exponents for the zero-temperature regime: <math altimg='si16.svg'><mrow><mi>&#945;</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn></mrow></math>, <math altimg='si17.svg'><mrow><mi>&#946;</mi><mo linebreak='goodbreak'>=</mo><mn>2</mn></mrow></math>, and <math altimg='si18.svg'><mrow><mi>&#947;</mi><mo linebreak='goodbreak'>=</mo><mi>d</mi><mo linebreak='goodbreak'>&#8722;</mo><mn>3</mn></mrow></math>, with <italic>d</italic> being the spacetime dimension. Moreover, we demonstrate that these exponents are robust, holding irrespective of the black hole&#8217;s charge and spin. Our study establish novel universal behavior in the semi-classical level in the low-temperature regime of black hole thermodynamics, and the resulting exponents serve as a necessary benchmark that any complete theory of quantum gravity must reproduce in its semi-classical limit.

China

Shao-Wen Wei

Shan-Ping Wu

Yu-Peng Zhang

Yu-Xiao Liu

Universal exponents of black hole phase transition at zero-temperature limit

In this short note we perform canonical analysis of Eddington gravity using L. Faddeev and Jackiw formalism. We demonstrate that resulting canonical action has the same form as General Relativity canonical action which proves an equivalence of Eddington gravity and General Relativity in Hamiltonian formalism.

Czechia

J. Klusoň

Canonical analysis of Eddington gravity

We solve the radical-square reflection residual of the symmetric elliptic free-fermion eight-vertex model in a minimal four-dimensional local coefficient algebra. Two parity-odd tangent channels generate an ordered product in the square of the radical, and the reflection equation fixes its parity-even completion within the trace-fixed sector whose radical-square term starts at order <italic>u</italic> 2. The resulting regular boundary object enters a double-row transfer construction. Its scalar quotient yields the open anisotropic XY Hamiltonian with diagonal boundary fields, while the full transfer object retains the non-semisimple boundary channels. Finite-chain audits through <math altimg='si1.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>12</mn></mrow></math> accompany the analytic construction.

Ze Tao

Hao Yan

Fujun Liu

Exact open anisotropic XY Hamiltonian from a non-semisimple boundary completion

A new measurement of the 2H( 15C, 3He) 14B reaction was conducted to investigate proton shell evolution in neutron-rich carbon and boron isotopes. The experiment employed a radioactive beam of 15C with a higher energy at 28.3 MeV/u and a large acceptance charged particle detector array LACPU, enabling coincident measurement of high-lying unbound states in 14B that include <italic>&#960;</italic>0 <italic>p</italic> <inf>1/2</inf>- <italic>&#960;</italic>0 <italic>p</italic> <inf>3/2</inf> transitions. A newly observed 3.45(35)-MeV resonance with a statistical significance of 3.1 <italic>&#963;</italic> in 14B exhibits <italic>&#960;</italic>0 <italic>p</italic> <inf>1/2</inf>- rather than <italic>&#960;</italic>0 <italic>p</italic> <inf>3/2</inf>-dominant character according to structural model predictions. The extracted proton spectroscopic factor of 0.16 &#8239;&#177;&#8239; 0.06 for 15C <inf>g.s.</inf> not only follows the systematic decreasing trend in neutron-rich carbon isotopes but also agrees with theoretical predictions, providing clear evidence for the <italic>Z</italic> = 6 magicity in 15C. Furthermore, systematic analysis of the energy splitting between the <italic>&#960;</italic>0 <italic>p</italic> <inf>3/2</inf> and <italic>&#960;</italic>0 <italic>p</italic> <inf>1/2</inf> orbitals in <math altimg='si4.svg'><msup><mrow /><mrow><mn>12</mn><mo>&#8722;</mo><mn>14</mn></mrow></msup></math>B reinforces the robustness of this magic number in neutron-rich nuclei systems.

H.Y. Zhu

J.L. Lou

Y.L. Ye

D.Y. Pang

M.R. Xie

J.G. Li

C.X. Yuan

S.L. Jin

Z.H. Yang

X.F. Yang

L.S. Yang

W.L. Pu

K. Wei

Y. Chen

Z.Y. Hu

B.L. Xia

H.Y. Ge

W.W. Wan

S.Q. Liang

J.H. Chen

K. Ma

J.X. Han

D.X. Wang

Q.T. Li

Z.H. Li

J.Y. Xu

H.Y. Wu

H.J. Ong

Y.Y. Yang

S.W. Xu

J.B. Ma

Zh. Bai

K. Wang

F.F. Duan

H.R. Yang

P. Ma

X.L. Wei

T.L. Qiu

<italic>Z</italic> = 6 magicity in 15C and 14B revealed by the 2H ( 15C, 3He) 14B reaction

In this paper, we investigate the Krylov complexity of the massless scalar field in the massive Bañados-Teitelboim-Zanelli (BTZ) black hole with quantum fluctuation. This fluctuation is considered to be triggered by the Hawking radiation, which indeed influences the behavior of the time evolution of Krylov complexity. Our results show that Lanczos coefficients <italic>b<inf>n</inf></italic> exhibit a black hole mass <italic>M</italic>-dependent staggering, <math altimg='si7.svg'><mrow><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle><mover><mrow><msub><mi>b</mi><mi>N</mi></msub></mrow><mo stretchy='true'>&#8254;</mo></mover><mo>&#8764;</mo><mi>M</mi></mrow></math>, inducing oscillatory complexity dynamics that intensify with lower mass black holes. Moreover, the graviton mass <italic>m</italic> is found to suppress the oscillations but accelerate the late-time exponential growth <math altimg='si8.svg'><mrow><mi>K</mi><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>&#8764;</mo><msup><mi>e</mi><mrow><msub><mi>&#955;</mi><mi>K</mi></msub><mi>t</mi></mrow></msup></mrow></math>. This study indicates that the Krylov complexity could be a sensitive probe to distinguish massless and massive gravity via operator growth signatures.

Yu-Ting Zhou

Xiao-Mei Kuang

Krylov complexity of a massless scalar field in massive BTZ black hole with quantum fluctuation