Hasil Pencarian  ::  Simpan CSV :: Kembali

Abstrak :
Dipelajari efek temperatur pada persamaan keadaan materi nuklir dan materi neutron pada bintang neutron. Perhitungan dilakukan dengan menggunakan model nuklir Walecka dengan pendekatan medan rata-rata. Penelitian difokuskan pada studi perubahan massa efektif, energi densitas, energi ikat dan tekanan, terhadap perubahan temperatur. ...... The temperature effects in the equation of state of nuclear and neutron matter in the neutron star are studied. The calculation are done by using Walecka Nuclear Model within Mean Field Approximation. The investigation focus are the change of effective mass, energy density, binding energy and pressure by increasing temperature.

Abstrak :
Hamburan neutrino dengan materi bintang quark melalui interaksi lemah arus ne- tral telah dipelajari. Untuk menjelaskan keadaan materi quark, digunakan model bag MIT. Struktur bintang quark dapat dipelajari dengan memasukkan persamaan keadaan bintang quark kedalam persamaan TOV. Dalam tulisan ini kami mempela- jari penampang lintang differensial dan lintasan bebas rata-rata neutrino. Perhitun- gan dilakukan menggunakan dua metode; Pertama dengan memperhatikan hambu- ran N-body sebagai N kali hamburan dua partikel, Kedua dengan memperlakukan efek banyak benda dengan baik dalam hamburan N-body. Kedua pendekatan dipela- jari dan dibandingkan pada kasus temperatur nol. Untuk pendekatan pertama, interaksi didominasi oleh quark down, sedangkan untuk pendekatan kedua quark down dan quark strange memberikan kontribusi yang sama. Lintasan bebas rata- rata neutrino menurun dengan meningkatnya kerapatan, temperatur dan energi awal neutrino. Untuk kasus temperatur berhingga, terdapat beberapa faktor yang perlu diperhatikan, seperti; faktor retardasi, Pauli blocking dan detailed balancing. Pauli blocking dan detailed balancing secara signifikan mengurangi nilai lintasan bebas rata-rata neutrino. Sedangkan faktor retardasi menunjukkan sifat yang tidak biasa dari lintasan bebas rata-rata neutrino-quark strange. Selain itu, efek penangkapan neutrino secara signifikan menyebabkan fraksi elektron meningkat. Kontribusi elek- tron menurunkan lintasan bebas rata-rata neutrino. Lebih lanjut, lintasan bebas rata-rata neutrino dari pusat bintang quark hingga ke permukaan bintang semakin meningkat. ......The scattering of neutrino with quark star matter through neutral current weak interaction is studied. To describe the quark matter state, MIT bag model is used. The quark star structures can be studied by inserted the quark star equation of state into TOV equation. Here we study the neutrino differential cross section and mean free path. The calculation is performed by using two method; First by considering N-body scattering as N times two body scattering, Second by treating the many body effect properly in N-body scattering. Both approach are compared and studied for the case zero temperature, where we have found that for the first approach, interaction are dominated by the one from down quark, while the second approach the down and strange quarks provide similar contribution. Neutrino mean free path decreases with increasing density, temperature and initial energy neutrino. For finite temperatur case are several factors should be considered, i.e, retardation, Pauli blocking and detailed balancing factors. Pauli blocking and detailed balancing significantly reduce the value of the neutrino mean free path. While the retardation factor indicates unusual behavior of neutrino-strange quark mean free path. In addition, the effect of neutrino trapping is significantly increased the fraction of electrons. Contribution of electrons reduces the value neutrino matter mean free path. Therefore, the neutrino mean free path from the center of quark star to the stellar surface increases.

Abstrak :
Dipelajari efek temperatur pada persamaan keadaan materi nuklir asimetrik. Perhitungan dilakukan dengan menggunakan model nuklir Walecka nonlinier diperumum dengan pendekatan medan rata-rata. Penelitian difokuskan pada studi efek temperatur pada kurva kestabilan mekanik, kestabilan kimia, dan koeksistensi fasa. Dan juga membandingkan kurva kestabilan mekanik, kestabilan kimia, dan koeksistensi fasa menggunakan parameter set yang berbeda pada temperatur tertentu.

---

The temperatur effect in the equation of state of asymetrik nuclear matter are studied. The Calculation are done by using generalized nonlinear Walecka nuclear model within mean field approximation. The investigation focus is on the temperatur effect of mechanical stabilty, chemical stability, and phase coexistance. And then we compare the curves of mechanical stabilty, chemical stability, and phase coexistance reproduced by different parameter set at finite temperature.

Abstrak :
Di alam semesta terdapat benda kompak yang merupakan sisa peluruhan dari evolusi bintang selama ratusan tahun. Salah satu benda kompak yang menarik untuk diteliti adalah bintang neutron. Karakteristik bintang neutron adalah ukurannya yang kecil dengan kerapatannya yang besar. Struktur bintang neutron didefinisikan dalam persamaan medan Einstein pada keadaan equilibrium yang disebut dengan persamaan Tolman,Oppenheimer dan Volkoff (TOV). Dalam keadaan isotropik, bintang neutron diasumsikan bersifat statis, bulat dan tidak berotasi. Penelitian mengenai bintang neutron dalam keadaan statik dan slow rotating sudah banyak dipelajari, namun penambahan efek konstanta kosmologi menjadi menarik untuk diteliti bagaimana pengaruhnya terhadap sifat bintang neutron. Pada keadaan slow rotating persamaan keadaan Einstein memiliki suku tambahan yang mengandung ω(r). Penambahan konstanta kosmologi (Λ) pada persamaan keadaan akan otomatis mengubah sifat bintang neutron. Perubahan terhadap massa-radius, momen inersia dan crust menjadi fokus yang dipelajari dalam penelitian ini. ......In the universe there are compact objects that are remnants of decay from the evolution of stars over hundreds of years. One compact object that is interesting to study is the neutron star. The characteristic of a neutron star is its small size and large density. The structure of a neutron star is defined in the Einstein field equation in a equilibrium state called the Tolman, Oppenheimer, and Volkoff (TOV) equation. In isotropic conditions, the neutron star is assumed to be static, spherical and not rotating. neutron star in static and slow rotating states have been widely studied, but the addition of the effects of cosmological constants is interesting to inverstigate how they affect the properties of neutron stars. In the slow rotating state, the Einstein state equation has an additional term containing ω(r). The addition of cosmological constants (Λ) to the state equation will automatically change the neutron stars nature. The changes of mass radius, moment of inertia and crust are the focus of this investigation.

Abstrak :
[ABSTRAK
Tumbukan ion berat menghasilkan suatu kondisi dimana jumlah proton dan neutron sama, hal ini disebut symmetric nuclear matter. Pemeriksaan terhadap karakteristik SNM masih dilakukan sampai saat ini. Efek suku non linear dianggap memberikan kontribusi terhadap karakteristik dari SNM, selain itu pemeriksaan terhadap kestabilan persamaan keadaan dilakukan dengan menggunakan metode medan rerata lanjutan. Pengecekkan lanjutan terhadap kestabilan persamaan energi dilakukan dengan mengamati nilai kecepatan suara untuk setiap parameter. Solusi dari persamaan densitas skalar, potensial skalar, dan turunan pertama potensial skalar ditunjukkan oleh titik potong ketiga kurva tersebut. Selain itu, pemeriksaan efek non linear terhadap kenaikan energi ikat dan tekanan setiap kenaikan temperatur juga diperiksa. Parameter G2 yang memiliki konstanta suku cross coupling terbukti memberikan kontribusi menahan laju kenaikan energi pada SNM, hal ini diperlihatkan oleh kurva parameter G2 merupakan kurva paling soft. Kurva parameter NLZ merupakan kurva paling stiff, serta memiliki nilai Cs paling besar saat nilai massa efektif tinggi. Kestabilan persamaan energi untuk setiap parameter masih dinilai realistik, ditinjau dari nilai C2s C2 < 1, namun setiap parameter memiliki daerahketidakstabilan saat massa efektif rendah karena nilai C2s negatif.

---

ABSTRACT
Heavy ion collision produces a condition where the total of proton equal with the total of the neutron this condition is named Symmetric Nuclear Matter SNM The investigation of SNM characteristic is still being done nowadays Effects of nonlinear term are considered to contribute to characteristics of SNM in addition to the examination of the stability equation of state were calculated using extended mean field method Advanced checking the stability of the energy equation is done by observing the sound velocity values each parameter The solution of scalar density equation scalar potential and first derivative of scalar potential are showed by crossing point of three curves The investigation of non linear effects to the binding energy increasing and pressure every rise of temperature G2 which has cross coupling term contributes to restrain increasing of SNM energy it is shown by the G2 parameter curve is softest NLZ is stiffest and has biggest Cs value when high effective mass condition The stability of energy equation every Heavy ion collision produces a condition where the total of proton equal with the total of the neutron, this condition is named Symmetric Nuclear Matter (SNM). The investigation of SNM characteristic is still being done nowadays. Effects of nonlinear term are considered to contribute to characteristics of SNM, in addition to the examination of the stability equation of state were calculated using extended mean field method. Advanced checking the stability of the energy equation is done by observing the sound velocity values each parameter. The solution of scalar density equation, scalar potential, and first derivative of scalar potential are showed by crossing point of three curves. The investigation of non linear effects to the binding energy increasing and pressure every rise of temperature. G2 which has cross coupling term contributes to restrain increasing of SNM energy, it is shown by the G2 parameter curve is softest. NLZ is stiffest, and has biggest Cs value when high effective mass condition. The stability of energy equation every parameter could be said mentioned realistic, it is considered from C2 s C2 < 1 value, but each parameter has instability region when low effective mass condition is happened, because the values C2 s are negative. , Heavy ion collision produces a condition where the total of proton equal with the total of the neutron this condition is named Symmetric Nuclear Matter SNM The investigation of SNM characteristic is still being done nowadays Effects of nonlinear term are considered to contribute to characteristics of SNM in addition to the examination of the stability equation of state were calculated using extended mean field method Advanced checking the stability of the energy equation is done by observing the sound velocity values each parameter The solution of scalar density equation scalar potential and first derivative of scalar potential are showed by crossing point of three curves The investigation of non linear effects to the binding energy increasing and pressure every rise of temperature G2 which has cross coupling term contributes to restrain increasing of SNM energy it is shown by the G2 parameter curve is softest NLZ is stiffest and has biggest Cs value when high effective mass condition The stability of energy equation every Heavy ion collision produces a condition where the total of proton equal with the total of the neutron, this condition is named Symmetric Nuclear Matter (SNM). The investigation of SNM characteristic is still being done nowadays. Effects of nonlinear term are considered to contribute to characteristics of SNM, in addition to the examination of the stability equation of state were calculated using extended mean field method. Advanced checking the stability of the energy equation is done by observing the sound velocity values each parameter. The solution of scalar density equation, scalar potential, and first derivative of scalar potential are showed by crossing point of three curves. The investigation of non linear effects to the binding energy increasing and pressure every rise of temperature. G2 which has cross coupling term contributes to restrain increasing of SNM energy, it is shown by the G2 parameter curve is softest. NLZ is stiffest, and has biggest Cs value when high effective mass condition. The stability of energy equation every parameter could be said mentioned realistic, it is considered from C2 s C2 < 1 value, but each parameter has instability region when low effective mass condition is happened, because the values C2 s are negative. Key words: coupling, soft, stiff. ix]

Abstrak :
Penelitian ini bertujuan untuk mengetahui sifat astrofisika dari bintang boson dua fluida dan perbandingannya dengan model bintang boson satu fluida pada temperatur nol dan temperatur tidak nol. Persamaan keadaan bintang boson dua fluida didapatkan pada sistem nonrelativistik dengan menggunakan representasi termodinamika serta memenuhi persamaan Gross-Pitaevskii. Penelitian ini dibatasi dengan pendekatan bahwa bintang dalam kondisi statik dan simetri bola. Persamaan keadaan bintang boson dua fluida dijadikan input Persamaan Tolman-Oppenheimer-Volkoff yang dikerjakan secara numerik dengan metode Runge-Kutta dan metode cari akar. Didapatkan relasi massa dengan jari-jari bintang boson dua fluida dengan massa maksimum pada temperatur nol dan temperatur tidak nol adalah sekitar 0.51m*. Diketahui juga bahwa pada sistem bintang boson dua fluida pada temperatur tidak nol terdapat daerah ketidakstabilan bintang pada saat tekanan dan densitas energi rendah (limit mendekati nol). ......The purpose of this study is to find out the astrophysical properties of two-fluid boson star and comparison with boson star at zero and non-zero temperature systems. The equation of state of two-fluid boson star in a non-relativistic system was found using thermodynamics representation which satisfies Gross-Pitaevskii approximation. This study is constrained to a static and spherically symmetric approximation. The equation of state of two-fluid boson star becomes an input for The Tolman-Oppenheimer-Volkoff equation which then is solved numerically using Runge-Kutta and root-finding method. We find the mass-radius relation of two-fluid boson star whose maximum mass at zero and non-zero temperature is about 0.51$m*$. We also find, in non-zero temperature system, that the two-fluid boson star has instability region in low pressure and low energy density (limit to zero).

Abstrak :
Penelitian mengenai bintang neutron telah banyak dilakukan, diantaranya adalah penelitian pada bintang neutron yang terdefromasi menggunakan persamaan TOV namun untuk keadaan medan magnet bintang yang isotropi. Adapun penelitian lainnya yang membahas mengenai formalisme relativitas umum dari bintang neutron dengan medan magnPenelitian mengenai bintang neutron telah banyak dilakukan, diantaranya adalah penelitian pada bintang neutron yang terdeformasi menggunakan pendekatan persamaan TOV namun untuk keadaan medan magnet bintang yang isotropi. Adapun penelitian lainnya ada yang membahas mengenai formalisme relativitas umum dari bintang neutron dengan medan magnet yang anisotropi. Sedangkan penelitian kali ini adalah penelitian yang coba mengakomodir kedua penelitian sebelumnya, yaitu penelitian pada bintang neutron yang mengalami deformasi dan dengan keadaan medan magnet yang anisotropi. Penelitian dilakukan dengan memodifikasi tensor metrik dan tensor-energi momentum untuk mengonstruksi persamaan gravitasi Einstein. Hasil akhir dari persamaan tersebut dapat menjelaskan bagaimana pengaruh deformasi dan medan magnet terhadap profil dari bintang neutron. ...... Many studies of Neutron Star have been done. Some research studied on deformed neutron star using TOV Equation approach, but with an isotropic magnetic field. Some are using the general relativity formalism of the neutron star with an anisotropic magnetic field. This research combine both of the methods, we study about a deformed neutron star with an anisotropic magnetic field. The research is to do some modification on metric tensor and the energy momentum tensor to construct the Einsteins gravitational equation. The final equation will show the effect of the deformation and magnetic field on the neutron star.

Abstrak :
ABSTRAK
Bentuk kompleksitas dari suatu sistem yang selanjutnya dikenal sebagai entropi konfigurasi dapat diterapkan untuk menentukan batas kestabilan dari objek astrofisika. Densitas energi sebagai fungsi yang terlokalisasi secara spasial dan terikat yang merupakan solusi dari persamaan efektif bintang dijadikan input untuk menghitung entropi konfigurasi dari bintang politropik dan bintang neutron. Disini bintang politropik dipelajari dalam limit non-relativistik dari teori gravitasi: Eddington inspired Born Infeld EiBI , dan cubic Gallileon Veinstein . Sementara bintang neutron dipelajari dalam gravitasi EiBI dengan menggunakan dua jenis persamaan keadaan: gas neutron dan baryon yang saling berinteraksi. Batas kestabilan dari masing-masing objek berdasarkan metode ini selanjutnya dapat digunakan untuk mengkonstrain parameter bebas dari masing-masing teori gravitasi termodifikasi.Kata Kunci: Entropi konfigurasi, bintang politropik, bintang neutron, teori gravitasi Eddington-inspired Born Infeld, teori gravitasi cubic Gallileon.

---

ABSTRACT
Shape complexity of a system which is known as configuration entropy can be applied to determine stability bounds on astrophysical objects. Energy density as spatially localized bounded function as solution of stellar effective equations are used to compute configuration entropy from polytropic stars and neutron stars. Here polytropic stars are studied within non relativistic limit of these modified gravities Eddington inspired Born Infeld EiBI , and cubic Gallileon Veinstein . Meanwhile, neutron stars are studied within EiBI gravity by using two kinds of equation of state neutron gas, and interacting baryons. Stability bounds on each objects based on this method can be used to constraint free parameters of each modified gravities. Keywords Configuration entropy polytropic stars neutron stars Eddington inspired Born Infeld gravity cubic Gallileon gravity.

Abstrak :
Teori gravitasi Eddington-inspired Born Infeld EiBI menyediakan ranah baru untuk kopling antara gravitasi-materi di luar relativitas umum Einstein. Kopling gravitasi-materi dipandang sebagai kontribusi anisotropik tambahan terhadap relativitas umum Einstein pada bintang. Struktur bintang dipelajari untuk persamaan keadaan bintang neutron politropik dan bintang neutron realistis. Massa dan radius bintang pada EiBI dengan materi anisotropik untuk ekspansi ? orde rendah mendekati struktur EiBI standar dengan kopling pada materi isotropik. Batas ? agar memenuhi kriteria bintang anisotropik bergantung pada stiffness persamaan keadaan bintang. Berdasarkan pendekatan ini, singularitas skalar Ricci dan Kretschmann tidak ditemukan di permukaan bintang. ......Eddington inspired Born Infeld theory of gravity EiBI provides a new playground for gravity matter coupling beyond general relativity GR . In this manuscript, I consider gravity matter coupling in EiBI as an additional anisotropic contribution to GR on stars. I show that for low order series expansion of parameter the structure of star are close to original theory. I also investigate some criteria for anisotropic star structure in this theory for polytropic and realistic neutron star equation of state EoS . The constraint of depends on the stiffness of EoS. Based on this approach, the singularity of Ricci and Kretschmann curvature scalar are not found at the surface of the star for first and second order expansion in this theory.