615.772.81 - Cosmology

Expanded Course Description

Modules 01-06:  We begin with a general overview of fundamental cosmological observations including the expansion of the universe.  We derive the Robertson-Walker metric describing the expanding universe using the principles of homogeneity and isotropy (valid for scales ~ 100 Mpc).  We study cosmic dynamics by deriving the Friedmann-Robertson-Walker (FRW) equations using the Einstein field equations.  We study several examples of model universes containing radiation, matter, and cosmological constant and describe the benchmark Lambda-CDM model that appears to best fit current observations including accelerated expansion.  We discuss relating cosmological parameters to measured quantities.  Finally we present the most important issues in modern cosmology and the solution offered by cosmic inflation.

Modules 07-12: We study gravitational lensing, dark matter and the CMBR including the physics of recombination and causes of temperature fluctuations.  We discuss nucleosynthesis in the early universe and the problem of observed baryon-antibaryon asymmetry.  Finally we discuss the formation of structure and the importance of baryon acoustic oscillations on placing constraints on cosmological models and parameters. 

Course Structure

The course materials are divided into modules which can be accessed by clicking Course Modules on the left menu.   Each module may be divided into more than one video, and includes an assignment. 

Modules become available on Saturdays 1 AM, so each module is available for approximately two weeks before required submission(s).

Course Topics

1. Relativistic cosmological models
2. Cosmological parameters
3. Inflation
4. Gravitational lensing
5. Dark matter
6. Structure formation
7. Cosmic background radiation

Course Goals

Thorough understanding of modern relativistic cosmological theory of an expanding universe, including concepts of dark matter, dark energy, and accelerated expansion, and relating observations to theoretical parameters.

Textbooks

"Introduction to Cosmology", 2nd edition, , Barbara Ryden, CUP, ISBN:  9-781107-154834

Student Coursework Requirements

• Weekly Assignment (50% of final grade)
• Final paper and Presentation (40% of final grade)
• Muddiest Points Discussion online submission (10% of final grade)

If you are asked to resubmit an assignment you have 3 days to do so to improve that grade to a maximum of 90%.  Late assignments will be graded according to the following schedule:
3 days late:  maximum grade is 80%
6 days late:  maximum grade is 60%
Later submissions will receive ZERO.

Grading Policy

Score Range	Letter Grade
100-98	= A+
97-94	= A
93-90	= A-
89-87	= B+
86-83	= B
82-80	= B-
79-77	= C+
76-73	= C
72-70	= C-
69-67	= D+
66-63	= D
<63	= F

Course Policies

Assignments are due according to the dates posted on the course site and the course schedule.  All assignments must be submitted in PDF format. Students should use LaTex, Word, or equivalent environments to produce a PDF output for submission.

The following grades are used for this course: A+, A, A- (excellent), B+, B, B- (good), C (unsatisfactory), F (failure), I (incomplete). A grade of F indicates the student's failure to complete or comprehend the course work. 

A course for which an unsatisfactory grade (C through F) has been received may be retaken. The original grade is replaced with an R. A grade of W is issued to those who have dropped the course after the refund period but before the drop deadline. The transcript is part of the student's permanent record at the university. No grade may be changed except to correct an error, to replace an incomplete with a grade, or to replace a grade with an R. 

The Whiting School assumes that students possess acceptable written command of the English language. It is proper for faculty to consider writing quality when assigning grades.  For incomplete grades, please see the Graduate Programs catalogue for the Whiting School of Engineering.

Student Generative AI (GenAI) Use

The decision to take a demanding graduate course in theoretical physics reveals a genuine passion for learning and not just a desire for a better position at work: the passion to learn new physics concepts, to build intuition using difficult mathematics, and to look for the meaning behind each mathematical step. 

Homework assignments in such classes are not just about getting the right final answers; they are a structured way for you to test your mathematical problem-solving skills, to train yourself to recognize patterns, and to give you confidence to navigate unfamiliar ground. 

Using GenAI to solve homework assignments destroys the ability for you to master any subject, not to mention that GenAI can introduce errors while providing a pretty “final answer” that is wrong. 

If you care about learning the greatest theories humans have devised then treat homework as sacred practice: ask for hints, check your own steps, and use GenAI only in supporting ways such as clarifying definitions, doing an integral, or verifying algebra after you’ve done the work yourself.  But always describe how GenAI helped you in the mathematics.  Asking GenAI or searching the web for a  solution to any specific assignment problem is, however, forbidden.

As for Discussion posts, you can use GenAI examples to help understand a concept you are having difficulty with, but explain how GenAI was used to help you overcome the conceptual difficulty.

If you have any questions please ask.

Academic Policies

Deadlines for Adding, Dropping, and Withdrawing from Courses

Students may add a course up to one week after the start of the term for that particular course. Students may drop courses according to the drop deadlines outlined in the EP academic calendar. Between the 6th week of the class and prior to the final withdrawal deadline, a student may withdraw from a course with a W on their academic record. A record of the course will remain on the academic record with a W appearing in the grade column to indicate that the student registered and withdrew from the course. 

Academic Misconduct Policy

All students are required to read, know, and comply with the Johns Hopkins University Krieger School of Arts and Sciences (KSAS) / Whiting School of Engineering (WSE) Procedures for Handling Allegations of Misconduct by Full-Time and Part-Time Graduate Students. This policy prohibits academic misconduct, including but not limited to the following: cheating or facilitating cheating; plagiarism; reuse of assignments; unauthorized collaboration; alteration of graded assignments; and unfair competition. Course materials (old assignments, texts, or examinations, etc.) should not be shared unless authorized by the course instructor. Any questions related to this policy should be directed to EP’s academic integrity officer at ep-academic-integrity@jhu.edu.

Students with Disabilities - Accommodations and Accessibility

Johns Hopkins University values diversity and inclusion. We are committed to providing welcoming, equitable, and accessible educational experiences for all students. Our courses are designed with a proactive approach to accessibility to minimize the need for disability disclosure and accommodation requests, but we recognize that you may need additional support. Students with disabilities (including those with psychological conditions, medical conditions, and temporary disabilities) can request accommodations for this course by providing an Accommodation Letter issued by Student Disability Services (SDS). Please request accommodations for this course as early as possible to provide time for effective communication and arrangements.  For further information or to start the process of requesting accommodations, please contact EP Student Disability Services at ep-disability-svcs@jhu.edu. 

Student Conduct Code

The fundamental purpose of the JHU regulation of student conduct is to promote and to protect the health, safety, welfare, property, and rights of all members of the University community as well as to promote the orderly operation of the University and to safeguard its property and facilities. As members of the University community, students accept certain responsibilities which support the educational mission and create an environment in which all students are afforded the same opportunity to succeed academically. For a full description of the code please visit the Student Conduct Code website.

Classroom Climate

JHU is committed to creating a classroom environment that values the diversity of experiences and perspectives that all students bring. Everyone has the right to be treated with dignity and respect. Fostering an inclusive climate is important. Research and experience show that students who interact with peers who are different from themselves learn new things and experience tangible educational outcomes. At no time in this learning process should someone be singled out or treated unequally on the basis of any seen or unseen part of their identity. If you have concerns in this course about harassment, discrimination, or any unequal treatment, or if you seek accommodations or resources, please reach out to the course instructor directly. Reporting will never impact your course grade. You may also share concerns with your program chair, the Assistant Dean for Diversity and Inclusion, or the Office of Institutional Equity. In handling reports, people will protect your privacy as much as possible, but faculty and staff are required to officially report information for some cases (e.g. sexual harassment).

Course Auditing

When a student enrolls in an EP course with “audit” status, the student must reach an understanding with the instructor as to what is required to earn the “audit.” If the student does not meet those expectations, the instructor must notify the EP Registration Team (EP-Registration@exchange.johnshopkins.edu) in order for the student to be retroactively dropped or withdrawn from the course (depending on when the "audit" was requested and in accordance with EP registration deadlines). All lecture content will remain accessible to auditing students, but access to all other course material is left to the discretion of the instructor.