This work presents the first experimental results on prompt neutron multiplicities from short-lived spontaneously fissioning isomers produced in the multinucleon transfer (MNT) reaction of 26Mg + 238U. The observed prompt neutron multiplicity distribution yields an average neutron number of <math altimg='si2.svg'><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover></math> = 2.65 &#8239;&#177;&#8239; 0.20 and a variance of <math altimg='si3.svg'><msubsup><mi>&#963;</mi><mrow><mi>&#957;</mi></mrow><mn>2</mn></msubsup></math> = 1.4. The half-life of the spontaneously fissioning products was determined to be <math altimg='si4.svg'><mrow><msub><mi>T</mi><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msub><mo linebreak='goodbreak'>=</mo><mn>5</mn><mo>.</mo><msubsup><mn>3</mn><mrow><mo>&#8722;</mo><mn>0.4</mn></mrow><mrow><mo>+</mo><mn>0.5</mn></mrow></msubsup><mspace width='0.16em' /><mi>&#956;</mi><mtext>s</mtext></mrow></math>. The shape of the multiplicity distribution of prompt fission neutrons was restored using the Tikhonov regularization technique and is characterized by a symmetrical distribution.

Kazakhstan

Russia

B. Sailaubekov

A.I. Svirikhin

H.M. Devaraja

A.V. Isaev

R.S. Mukhin

M.A. Bychkov

M.L. Chelnokov

V.I. Chepigin

V.D. Danilkin

I.N. Izosimov

Sh A. Kalandarov

D.E. Katrasev

A.A. Kuznetsova

O.N. Malyshev

A.G. Popeko

Yu A. Popov

E.A. Sokol

E. Teymurov

M.S. Tezekbayeva

I.I. Ulanova

First investigation of prompt neutrons from spontaneously fissioning isomers produced in multinucleon transfer reactions

The relative correlation between the magnitudes of elliptic flow ( <italic>v</italic> <inf>2</inf>) and triangular flow ( <italic>v</italic> <inf>3</inf>) has been accurately measured in nucleus-nucleus collisions at the LHC collider. As a function of the centrality of the collision, it changes sign and varies non-monotonically. We show that this is naturally explained by two combined effects. The first effect is a skewness in initial-state fluctuations, which is quantified by the correlation between the geometry-driven elliptic deformation in the reaction plane and the fluctuation-driven triangularity &#949; <inf>3</inf>. We introduce an intensive measure of this skewness, which is generically of order unity and varies little above 5 % centrality. We evaluate its magnitude using Monte Carlo simulations of the initial state, which show that it is sensitive to the nucleon width. The second effect is the fluctuation of impact parameter relative to centrality classifiers used by experiment. The ATLAS collaboration uses two different centrality classifiers, the multiplicity <italic>N<inf>ch</inf></italic> and the transverse energy <italic>E<inf>T</inf></italic>. We fit both sets of results for Pb+Pb collisions up to &#8239;&#8776;&#8239;40&#8201;% centrality with a single parameter, the intensive mixed skewness. Its value inferred from experiment agrees with theoretical expectations.

Saudi Arabia

Mubarak Alqahtani

France

Jean-Yves Ollitrault

Understanding the correlation between elliptic and triangular flow

Gravitational waves sourced by amplified scalar perturbations are a common prediction across a wide range of cosmological models. These scalar curvature fluctuations are inherently nonlinear and typically non-Gaussian. We argue that the effects of non-Gaussianity may not always be adequately captured by an expansion around a Gaussian field, expressed through nonlinear parameters such as <italic>f</italic> <inf>NL</inf>. As a consequence, the resulting amplitude of the stochastic gravitational wave background may differ significantly from predictions based on the standard quadratic source model routinely used in the literature.

Italy

Switzerland

A.J. Iovino

S. Matarrese

G. Perna

A. Ricciardone

A. Riotto

How well do we know the scalar-induced gravitational waves?

We formulate an argument, based on the use of the action-angle variables and the Bohr-Sommerfeld quantization rule, to the effect that if there exists the smallest possible non-zero area, there also exists, for massive particles, the largest possible observable speed, which is a bit less than the speed of light.

Finland

Jarmo Mäkelä

Action-angle variables in quantum gravity

Thermoelectric phenomena are traditionally associated with the interconversion of thermal and electrical energy in many-body systems. In the context of high-temperature quantum chromodynamics (QCD) matter produced in relativistic heavy-ion collisions, thermoelectric responses can provide insight into the evolving microscopic dynamics and the redistribution of effective degrees of freedom across the phase transition region. In this work, for the first time, we present a phenomenological study of the thermoelectric figure of merit ( <italic>ZT</italic>) in hot QCD matter, with a particular focus on its behavior across the hadronic and quark-gluon plasma phases. Using model-based calculations for the electrical conductivity, Seebeck coefficient, and thermal conductivity, we analyze the temperature dependence of <italic>ZT</italic> and identify characteristic features near the QCD phase transition temperature. Our results indicate that <italic>ZT</italic> exhibits nontrivial behavior near the transition region, reflecting the changing transport properties and active degrees of freedom in the medium. This phenomenological study of the thermoelectric figure of merit provides a complementary perspective to traditional transport studies and may provide critical insights for advancing the understanding of QCD matter through the transition region.

India

Kamaljeet Singh

Raghunath Sahoo

Thermoelectric figure of merit and the deconfinement phase transition

We investigate Power-Law Plateau (PLP) inflation in standard gravity and its consistency with ACT DR6 data. While many inflationary models, including the Starobinsky inflation, are disfavored by ACT observations, the PLP potential remains viable across a broad range of its parameters. Then, the dynamics of the reheating phase are investigated, with a primary focus on the reheating temperature and its relationship with the inflationary phase and primordial gravitational waves. Incorporating the overproduction of the primordial gravitational waves can affect the effective number of relativistic species during reheating. The constraint on Δ <italic>N</italic> <inf>eff</inf> can impose a lower bound on the reheating temperature. This constraint will be more efficient for a stiff equation of state. It is determined that for <italic>w<inf>re</inf></italic>&#8239;&#8819;&#8239;0.58, this constraint would be efficient. Combining the result of the reheating temperature and the inflationary phase, it is concluded that to have both a viable result standing in 1 <italic>&#963;</italic> of ACT DR6 and also to satisfy the reheating lower bound, the number of remaining e-folds of inflation after the pivot scale exits the horizon should be <italic>N<inf>k</inf></italic>&#8239;&#8818;&#8239;62. Higher e-folds of expansion result in a reheating temperature below the bound, which is disfavored. Finally, for the constraint values of the reheating temperature, the energy spectrum of the primordial gravitational waves (PGWs) has been explored. The results indicate that there is a higher chance of detection of PGWs for lower reheating temperatures and higher reheating equation of state. We also address the condensate fragmentation during reheating for stiff <italic>w<inf>re</inf></italic>&#8239;&#8805;&#8239;0.58. It is discussed that for our model, the stiff phase could last for some e-folds before <italic>w<inf>re</inf></italic>&#8239;&#8594;&#8239;1/3. This leads to a larger reheating temperature <italic>T<inf>re</inf></italic>, however, the resulting PGWs energy spectrum is suppressed and it is below the detectable level.

China

Abolhassan Mohammadi

 Yogesh

United States

Anzhong Wang

Power law plateau inflation and primordial gravitational waves in the light of ACT

In this article, the vector, axial vector and tensor form factors of <italic>B<inf>c</inf></italic> to <italic>D</italic>-wave charmonia <italic>&#968;<inf>J</inf></italic> ( <math altimg='si138.svg'><mrow><mi>J</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>,</mo><mn>3</mn></mrow></math>) and <italic>&#951;</italic> <inf><italic>c</italic>2</inf> are analyzed within the framework of three-point QCD sum rules. With the predicted vector and axial vector form factors, we study the decay widths and branching ratios of semileptonic decays <math altimg='si139.svg'><mrow><msub><mi>B</mi><mi>c</mi></msub><mo>&#8594;</mo><msub><mi>&#968;</mi><mi>J</mi></msub><mi>l</mi><mover accent='true'><msub><mi>&#957;</mi><mi>l</mi></msub><mo>&#175;</mo></mover></mrow></math> and <math altimg='si140.svg'><mrow><msub><mi>B</mi><mi>c</mi></msub><mo>&#8594;</mo><msub><mi>&#951;</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub><mi>l</mi><mover accent='true'><msub><mi>&#957;</mi><mi>l</mi></msub><mo>&#175;</mo></mover></mrow></math>. Our results indicate that the semileptonic decay branching ratios of <italic>B<inf>c</inf></italic> to <italic>D</italic>-wave charmonia decreases as the total angular momentum of the final state <italic>D</italic>-wave charmonia increases. For decay processes <math altimg='si141.svg'><mrow><msub><mi>B</mi><mi>c</mi></msub><mo>&#8594;</mo><msub><mi>&#968;</mi><mn>1</mn></msub><mi>l</mi><msub><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>l</mi></msub></mrow></math>, <math altimg='si142.svg'><mrow><msub><mi>B</mi><mi>c</mi></msub><mo>&#8594;</mo><msub><mi>&#968;</mi><mn>2</mn></msub><mrow><mo>[</mo><msub><mi>&#951;</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub><mo>]</mo></mrow><mi>l</mi><msub><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>l</mi></msub></mrow></math> and <math altimg='si143.svg'><mrow><msub><mi>B</mi><mi>c</mi></msub><mo>&#8594;</mo><msub><mi>&#968;</mi><mn>3</mn></msub><mi>l</mi><msub><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>l</mi></msub></mrow></math>, the branching ratios can reach the order of magnitude <math altimg='si100.svg'><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>3</mn></mrow></msup></math>, <math altimg='si144.svg'><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></math> and <math altimg='si145.svg'><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>5</mn></mrow></msup></math>, respectively, which can provide a valuable reference for future experimental measurements for <italic>B<inf>c</inf></italic> meson by LHCb collaboration. Furthermore, these results also can provide useful information to study the properties of <italic>B<inf>c</inf></italic> meson and <italic>D</italic>-wave charmonia.

Jie Lu

Dian-Yong Chen

Guo-Liang Yu

Zhi-Gang Wang

Systematic analysis of the transition form factors of <italic>B<inf>c</inf></italic> to <italic>D</italic>-wave charmonia and corresponding semileptonic decays

The structure of the <math altimg='si35.svg'><msubsup><mrow /><mn>22</mn><mn>43</mn></msubsup></math>Ti <inf>21</inf> nucleus has been explored employing correlations between delayed and prompt <italic>&#947;</italic> rays, leading to a substantial extension of its positive-parity yrast band up to 25/2 <math altimg='si36.svg'><msup><mrow /><mo>+</mo></msup></math>. New states were were identified using the isomer-tagging technique together with <math altimg='si37.svg'><mrow><mi>&#947;</mi><mspace width='0.16em' /><mo linebreak='goodbreak'>&#8722;</mo><mspace width='0.16em' /><mi>&#947;</mi></mrow></math> coincidences and were compared to the analogue states in the mirror nucleus <math altimg='si38.svg'><msubsup><mrow /><mn>21</mn><mn>43</mn></msubsup></math>Sc <inf>22</inf>. The Mirror Energy Differences (MED) between analogue states have been extracted and compared to the predictions from the Large-Scale Shell-Model calculations in two main shells. For the positive-parity states which involve particle-hole excitations from the <italic>sd</italic> to the <italic>fp</italic> shell, a striking correlation between the measured MED and the type of nucleons excited across the shell gap is observed. This is reinforced by the systematic behavior of non-natural parity MED for nuclei across the entire <italic>f</italic> <inf>7/2</inf> shell, which puts in evidence that experimental MED serve as direct, sensitive probes of the underlying microscopic structure of nuclear wave function.

K. Rezynkina

A. Illana Sison

S.M. Lenzi

F. Recchia

P. Ruotsalainen

P. Aguilera

K. Auranen

J. Benito

S. Carollo

M.L. Cortes

R. Escudeiro

T. Grahn

P.T. Greenlees

South Korea

J. Ha

R. Julin

H. Joukainen

H. Jutila

M. Leino

J. Louko

M. Luoma

D. Napoli

J. Ojala

J. Pakarinen

S. Pigliapoco

Spain

A. Poves

P. Rahkila

M. Sandzelius

J. Sarén

A. Tolosa-Delgado

J. Uusitalo

G.L. Zimba

Mirror energy differences between 43Ti and 43Sc: A direct insight into the nuclear wave functions

We use the Tomonaga–Schwinger (TS) formulation of quantum field theory to determine when state-dependent additions to the local Hamiltonian density (i.e., modifications to linear Schrödinger evolution) violate relativistic covariance. We derive new operator integrability conditions required for foliation independence, including the Fréchet derivative terms that arise from state-dependence. Nonlinear modifications of quantum mechanics affect operator relations at spacelike separation, leading to violation of the integrability conditions.

Stephen D.H. Hsu

Relativistic covariance and nonlinear quantum mechanics: Tomonaga-Schwinger analysis

We study the effect on the primordial tensor power spectrum of varying the number of e-folds during slow-roll inflation in Loop Quantum Cosmology with a Starobinsky potential. Using the hybrid quantization approach, we derive the effective mass governing tensor mode evolution. The choice of vacuum state is crucial, especially since the preinflationary phase predicted by Loop Quantum Cosmology invalidates the choice of the Bunch-Davies state as the preferred vacuum. We adopt a choice which is optimally adapted to the dynamics, so that it provides a non-oscillating (NO) spectrum free of spurious contributions, and permits an asymptotic Hamiltonian diagonalization (AHD) of the perturbations. For this so-called NO-AHD vacuum, we compute the power spectrum using both analytic approximations and numerical integration. Our results confirm the accuracy of our approximations in a wide range of situations, including short- and long-lived inflationary scenarios. The primordial power spectrum exhibits a characteristic cutoff on a wavenumber scale determined primarily by the background dynamics around the bounce that replaces the big bang in Loop Quantum Cosmology.

Marceau Henry

Guillermo A. Mena Marugán

Antonio Vicente-Becerril

Starobinsky potential and power suppression in hybrid loop quantum cosmology