Anto Sulaksono

The origin of the neutron skin thickness, measured by the CREX and PREX collaborations as thin for 40 Ca and thick for 28 Pb, remains a mystery. We investigate the effects of tensor and nonlinear isovector–isoscalar terms in a relativistic mean-field model (RMF) on the properties of finite nuclei and nuclear matter. Tensor couplings are crucial for better quality binding energies of finite nuclei and charge radii for relatively heavy nuclei. However, for light nuclei, the tensor terms cannot improve the compatibility of charge radius predictions by the RMF model with experimental data. We find that parameter sets with a larger nonlinear isovector–isoscalar parameter, particularly η 2 ρ= 0.028, agree better with experimental data for Δ r n p across light, medium, and heavy isotope chains. Using PT28, we calculate Δ r n p for 208 Pb as 0.214 fm, J as 33.078, and L as 58.426. Δ r n p for 208 Pb obtained using PT28 is …

The Cisterna-Delsate-Rinaldi (CDR) model is a variant of scalar-tensor theory that modify gravity by including a term of non-minimal derivative coupling. This model gives interesting aspects in the properties of compact objects, specifically neutron stars. By adjusting one of its parameters, the maximum possible mass of neutron stars can be increased. The authors of the model had also did a perturbation analysis using odd-parity perturbation and following that they also did analysis on the slowly-rotating neutron stars. In this paper, we report our ongoing research on the linear perturbation for the Cisterna model to see its dynamical properties. More precisely, we work on the polar perturbation that affected both the metric and the scalar field, which is different from the axial perturbation used in the slow rotation case. We use higher-dimensional spacetimes to see if the obtained equations will be dimensionally …

New observational data measured with high degree of accuracy of compact isolated neutron stars and binary stars in gravitational wave remnants have the potential to explore the strong field gravity. Within the framework of energy-momentum squared gravity (EMSG) theory, we study its impact on several properties of neutron stars and plausible modifications from the predictions of general relativity. Based on a representative set of relativistic nuclear mean field models, nonrelativistic Skyrme-Hartree-Fock models, and microscopic calculations, we show deviations of neutron star mass-radius sequence in EMSG theory as compared to general relativity. The variation in the effective nuclear equation of state in EMSG results in distinct magnitudes in the reduced pressure, speed of sound, and maximum compactness at the center of neutron stars. We perform extensive correlation analysis of the nuclear model …

We have previously shown [R. Rizaldy, AR Alfarasyi, A. Sulaksono, and T. Sumaryada, Phys. Rev. C 100, 055804 (2019)] that Fermi-surface distortion can affect nuclear matter and neutron star (NS) properties within the relativistic mean-field formalism. However, our previous results had the caveat that the k f/M*< 1 approximation was used. This approximation needs revision for high-density NS cases. This work proposes a more refined approximation in calculating the Fermi-surface distortion correction. We reinvestigate the consequences in nuclear and NS matter. The new expressions of the corresponding nucleon densities, energy density, and pressures are shown. The behavior of the predictions in high-density regions is studied. We found a better convergence of results for higher δ values than in the previous work. We also found that all recent experimental observations and other calculations constrain the …

We investigate how much the Newtonian-scale gravity within alternative coupling theory agrees with our understanding of Earth’s atmosphere. We compare the atmospheric pressure structure predicted by the Minimal Exponential Measure (MEMe) model with one from US Standard Atmosphere 1976 model which deviates less than 10% from observation. By using Bayesian analysis via Markov-chain Monte Carlo, we found that, to be able to consistently reproduce our current understanding of Earth’s atmosphere structure, the parameter q should yield| q|< 3.06× 10− 14 m3J− 1 in 2σ credibility, comparable to the constraint from GW170817 standard siren. We also compare this value with bounds from Eddington-inspired Born-Infeld gravity, which share a similar Poisson equation in Newtonian-scale.

We implement a recent model proposed by Serrano–Liska (SL) (Alonso-Serrano and Liška, JHEP, 12:196, 2020) to study the ultra-compact star properties. The matter in the interior star is modeled by the quark model, deducted from QCD theory equipped with anisotropic pressure. Anisotropy is used to increase the compactness of the stars. We intend to see the signature of the “quantum gravity” effect through the SL model in ultra-compact stars. The SL model was motivated by quantum correction appearing in the black hole by adding a logarithmic term in gravity entropy used to derive the effective Einstein field equation. We expect this correction term in the SL model also affects ultra-compact star properties. The SL model with coupling constant in logarithmic term equipped with spherically symmetric metric yields correction terms that can be expressed by a function . The function vanishes at the star’s exterior. We found that the …

Tests have to be performed to rule out proposals for gravity modification. We propose a new idea for constraining alternative theories of gravity using temperature-dependent white dwarf (WD) mass-radius (MR) observational data. We have shown that several alternatives to general relativity (GR), which modified GR only within matter, might be reduced to the well-known Poisson equation similar to that of Eddington-inspired Born Infeld (EiBI) and Minimal Exponential Measure (MEMe) gravity. Retaining EiBI notation, we constrain the value of the coupling constant, , using a high-precision model-independent measurement of WD MR observations. We have demonstrated that the WD model should include detailed physics to achieve good precision. The model should include their temperature and evolutionary aspects, which may be computationally expensive. To overcome this issue, we construct a semi-analytical surrogate model based on Mestel’s …

One of the compact objects that are attractive for investigating their energy conditions is quark stars. The existence of radial and tangential pressure differences in quark stars can cause anisotropic effects on the stars. We focus on and examine the energy conditions of quark stars using the Einstein Field Equation Solution. The energy stability of an anisotropic quark star can be determined by evaluating the profile of the pressure and energy density of the star using the anisotropic EOS as an input. The used equation is the extended MIT Bag Model, which involves the constant B and interaction parameter a 4 and the corresponding parameters of anisotropic part. It is known that parameter a 4 affects the mass distribution of quark stars to be more anisotropic. This anisotropic pressure also affects the energy condition profile of the star. We find the energy state of an anisotropic quark star satisfies the energy state of an …

Tolman VII (TVII) is an analytical model for the nonrotating perfect fluid sphere with a simple quadratic density profile where its value is zero at the surface and a finite critical density value at the center. Therefore, compared to another analytical model like the constant density star, TVII is more realistic. Except for the dominant energy condition (DEC), which is violated in the region near the star’s center, the TVII satisfies all energy conditions. However, the causal condition is also violated for C> 0.26, and the maximum compactness of the TVII is restricted, ie, C max≈ 0.38. Here, we investigate the impacts of nonlocal gravity on the properties of the star of TVII within the range of the compactness of an ultracompact star (0.33≤ C≤ 0.44). This nonlocal gravity version of TVII (NGTVII) is parametrized by the nonlocal parameters (β) and the compactness (C). We have found that NGTVII can reach C max= 0.43 with β max= 3 …

We implement the Doneva-Yazadjiev (DY) anisotropic model of neutron stars into Energy Momentum Squared Gravity (EMSG) theory. We have shown that the Tolmann-Oppenheimer-Volkoff (TOV) equation within this model can be expressed in the terms of effective pressure and energy density. The structure of neutron stars (NS) is then calculated by using Basic Standard Parameter equation of state with hyperons in the center. We found that the combined model is able to adjust the mass-radius relation of the NS. We also found that this model could affect boundary limit of EMSG parameter, α, in the term of stability.

This work is motivated by the existence of mapping the extended theory of gravity with a standard energy-momentum tensor to general relativity with a modified energy-momentum tensor. We construct a modified anisotropic energy-momentum tensor from a standard isotropic energy-momentum tensor by adding a “geometrical correction” to precisely reproduce the Tolman-Oppenheimer-Volkoff equations predicted by the generalized Tolman-Oppenheimer-Volkoff (GTOV) model. This construction aims to calculate the moment of inertia (I) and tidal deformability (Λ) of neutron stars (NSs) within the GTOV model. Therefore, we can comprehensively investigate the role of each free parameter of the GTOV model in NS properties. Furthermore, through this construction we can also utilize physically acceptable stability conditions for anisotropic stars to constrain the physical range of each parameter value and investigate …

Nucleus deformation refers to a change in the nucleus surface shape. The expression of the radius of the nucleus can represent this deformation. Generally, these radii are expansions involving spherical harmonics. In addition, some divide the nucleus shape into three parts. The left and right ends are spherical, while the middle or neck uses the hyperbolic function. The deformation shape does not contain the fraction of the nucleus fragments. In fact, including all possible fraction values will provide all the probability that occurs. These probabilities can be accumulated to determine the value of the potential barrier height. Based on this reason, a technique was developed to include the fragment fraction as part of the input variable. This technique is intended to be able to use experimental data from fission products. Namely, as input to get a potential barrier height. By changing the function expression for the radius of …

In this paper, we employ one variant of the Generalized Uncertainty Principle (GUP) model, i.e., the Kempf–Mangano–Mann (KMM) model, and discuss the impact of GUP on the EoS of nuclear and neutron star matter based on the relativistic mean field (RMF) model. We input the result in the Serrano–Liška (SL) gravity theory to discuss the corresponding Neutron Star (NS) properties. We have shown that the upper bound for the GUP parameter from nuclear matter properties is MeV. If we used this upper bound to calculate NS matter, and considering SL parameter as an independent parameter, we have found that the upper bound for the SL parameter, which modifies the Einstein field equation, is m. This beta upper bound is determined by considering the anisotropy magnitude smaller than the pressure magnitude. By employing MeV and m, we obtain the mass–radius relation that satisfies NICER data for both PSR …

Abstract Effects of neutrino charge radius and magnetic moment constraints obtained from the astrophysical observations and reactor experiments, as well as in-medium modifications of the weak and electromagnetic nucleon form factors of the matter on the neutrino electroweak interaction with dense matter, are estimated. We use a relativistic mean-field model for the in-medium effective nucleon mass and quark-meson coupling model for nucleon form factors. We analyze the neutrino scattering cross section and mean free path in cold nuclear matter. We find that the increase of the cross section relative to that without neutrino form factors results in the decrease of the neutrino mean free path when neutrino form factors and the in-medium modifications of the nucleon weak and electromagnetic form factors are simultaneously considered. The quenching of the neutrino mean free path is evaluated to be about 12-58 …

Previous studies showed that the intensity of electric fields (EF) preferentially inhibits cancer cell division during mitosis at intermediate frequencies. Cancer cells have different physiological activities from normal cells, resulting in different electrical activities between the cancer cells and the surrounding normal tissue. Many researchers have researched the effects of EF intensity distribution on cancer cell division utilizing EF intensity distribution measurement. However, variations in cancer cells' surrounding tissue and cancer cells are due to electric properties property differences that have not been studied well. The acting force varies with different media surrounding tumor mass and affects treatment effectiveness. To verify the EF's role in the cancer cell division, we developed a wired mesh tomography (WMT) sensor to measure EF intensity distributions inside and around the tumor phantom with different …

Quantum gravitational effects on the near horizon may alter the black hole’s horizon drastically to be partially reflective, portrayed by a quantum membrane. With this modification, the object can be considered as an exotic compact object (ECO). Quantum effects on the strong gravitational regime may also lead to a non-conserved matter tensor that can be described phenomenologically using Rastall gravity. In this work, we study the properties of black holes and ECOs within Rastall gravity using Kerr/CFT correspondence. We systematically investigate the properties of the most general rotating black hole solutions in Rastall gravity, i.e., Kerr–Newman-NUT-Kiselev, and reveal its hidden conformal symmetry. The Cardy microscopic entropy formula and absorption cross-sections from 2D CFT are computed and then matched with gravity calculation. We also extend the dual CFT analysis for studying the properties of …

The isotropy of space is not a logical requirement but rather is an empirical question; indeed there is suggestive evidence that universe might be anisotropic. A plausible source of these anisotropies could be quantum gravity corrections. If these corrections happen to be between the electroweak scale and the Planck scale, then these anisotropies can have measurable consequences at short distances and their effects can be measured using ultra sensitive condensed matter systems. We investigate how such anisotropic quantum gravity corrections modify low energy physics through an anisotropic deformation of the Heisenberg algebra. We discuss how such anisotropies might be observed using a scanning tunnelling microscope.

The results of gravitational wave GW 170817, which was observed after the binary neutron star merger, can be put to use for tightly constraining the mass and radius of neutron stars. We calculate the mass and radius of neutron stars using a parameterized post-TOV model. The model has several free parameters that provide more flexibility than that of standard general relativity (GR) compared to the observational data. We have found that for a particular combination of the corresponding free parameters, the post-TOV model's mass-radius predictions are compatible with those of GW170817 data.

Researchers have used electric fields as a new therapeutic strategy to treat cancer for the past 15 years. Tumor Treating Fields (TTFields) is an alternating electric field-based cancer therapy approved by the US FDA to treat glioblastoma multiforme (GBM). ECCT (Electro-Capacitive Cancer therapy), a DC charged-discharged electric field (EF) cancer therapy, also shows a performance inhibiting cell proliferation. ECCT affects the cancer lesions to cause simultaneous death of the cancer cell and detached off of the surrounding tissue. The author hypothesizes that the EF produces an electric force that is not homogeneous throughout the tumor mass and generates a strong dielectrophoresis force. The force affects microtubules polymerization during mitosis and causes mitotic arrest. To examine this hypothesis, we performed a numerical simulation of the EF distribution and calculated the force acting on the tumor mass generated by the EF. We analyzed DC electric field exposure on a cancer lesion using a single lesion 2D circular model, calculated the EF intensity on the lesion using the Finite Element Method, and the dielectrophoresis force distribution to quantify the treatment efficacy. The results showed that the distribution of EF intensity was not homogeneous at the lesion-medium boundary and homogeneous within the lesion. The EF intensity is highly dependent on the dielectric constant of the medium and the applied voltage difference that may affect the effectiveness of the treatment. Variations in lesion diameter had no significant effect on the EF intensity distribution and, hence the effectiveness of the therapy. It is considered that EF …

In a recent paper by Carballo-Rubio [Phys. Rev. Lett. 120, 061102 (2018)], the author proposed an ultra-compact object model, ie, a combination of black stars and gravastars, from semi-classical gravity to obtain a generalized Tolman-Oppenheimer-Volkoff (TOV) equation with a new coupling constant lp. The resulting TOV equations have two different forms differentiated by the sign in metric function equation dgtt/dr. In the limit lp→ 0, the second (respectively, the first) form of the equations from the negative (positive) sign is (is not) going back to the TOV equation. By defining a suitably new constant parameter λ, the author has found a solution from the first form of obeying boundary conditions. In this work, we investigate the model in a vacuum to obtain exterior solutions for the model. We calculate its exterior solutions using the perturbation method by a small parameter α= lp/rs where rs= 2GM is the Schwarzschild …