Charged particle multiplicity fluctuations in Pb-Pb collisions are studied for the central events generated using EPOS3 (hydro and hydro+cascade) at <math id="M2"><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></mrow></msqrt><mo>=</mo><mn>2.76</mn><mtext> </mtext><mtext>TeV</mtext></math>. Intermittency analysis is performed in the midrapidity region in two-dimensional (<math id="M3"><mi>η</mi></math>, <math id="M4"><mi>ϕ</mi></math>) phase space within the narrow transverse momentum (<math id="M5"><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math>) bins in the low <math id="M6"><msub><mrow><mtext>p</mtext></mrow><mrow><mtext>T</mtext></mrow></msub></math> region (<math id="M7"><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo>≤</mo><mn>1.0</mn><mtext> </mtext><mtext>GeV</mtext><mo>/</mo><mi>c</mi></math>). Power-law scaling of the normalized factorial moments with the number of bins is not observed to be significant in any of the <math id="M8"><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math> bins. Scaling exponent <math id="M9"><mi>ν</mi></math>, deduced for a few <math id="M10"><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math> bins, is greater than that of the value 1.304, predicted for the second-order phase transition by the Ginzburg-Landau theory. The link in the notions of fractality is also studied. Generalized fractal dimensions, <math id="M11"><msub><mrow><mi>D</mi></mrow><mrow><mi>q</mi></mrow></msub></math>, are observed to decrease with the order of the moment <math id="M12"><mi>q</mi></math> suggesting the multifractal nature of the particle generation in EPOS3.

India

Salman Khurshid Malik

Ramni Gupta

Intermittency Study of Charged Particles Generated in Pb-Pb Collisions at Using EPOS3

From the events generated from the MC code of a multiphase transport (AMPT) model with string melting, the properties of multiplicity fluctuations of charged particles in <math id="M1"><mi>P</mi><mi>b</mi><mo>–</mo><mi>P</mi><mi>b</mi></math> collisions at <math id="M2"><mrow><msqrt><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></mrow></math> = 2.76 TeV are studied. Normalized factorial moments, <math id="M3"><mrow><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub></mrow></math>, of spatial distributions of the particles have been determined in the framework of intermittency. Those moments are found in some kinematic regions to exhibit scaling behavior at small bin sizes, but not in most regions. However, in relating <math id="M4"><mrow><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub></mrow></math> to <math id="M5"><mrow><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math> scaling behavior is found in nearly all regions. The corresponding scaling exponents, <math id="M6"><mrow><mi>ν</mi></mrow></math>, determined in the low transverse momentum (<math id="M7"><mrow><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></mrow></math>) region ≤ 1.0 GeV/c are observed to be independent of the <math id="M8"><mrow><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></mrow></math> bin position and width. The value of <math id="M9"><mrow><mi>ν</mi></mrow></math> is found to be larger than 1.304, which is the value that characterizes the Ginzburg-Landau type second-order phase transition. Thus there is no known signature for phase transition in the AMPT model. This study demonstrates that, for the system under investigation, the method of analysis is effective in extracting features that are relevant to the question of whether the dynamical processes leading phase transition are there or not.

Rohni Sharma

Scaling Properties of Multiplicity Fluctuations in the AMPT Model

We point out a potential relevance between the Krein–Gupta–Bleuler (KGB) vacuum leading to a fully covariant quantum field theory for gravity in de Sitter (dS) spacetime and the observable smallness of the cosmological constant. This may provide a formulation of linear quantum gravity in a framework amenable to developing a more complete theory determining the value of the cosmological constant.

China

Hamed Pejhan

Japan

Kazuharu Bamba

Iran

Mohammad Enayati

Surena Rahbardehghan

A small non-vanishing cosmological constant from the Krein–Gupta–Bleuler vacuum

In this paper, vacuum expectation value (VEV) of the energy–momentum tensor for a conformally coupled scalar field in de Sitter space–time is investigated through the Krein–Gupta–Bleuler construction. This construction has already been successfully applied to the de Sitter minimally coupled massless scalar field and massless spin-2 field to obtain a causal and fully covariant quantum field on de Sitter background. We also consider the effects of boundary conditions. In this respect, Casimir energy–momentum tensor induced by Dirichlet boundary condition on a curved brane is evaluated.

S. Rahbardehghan

H. Pejhan

The Krein–Gupta–Bleuler quantization in de Sitter space–time; Casimir energy–momentum tensor for a curved brane